2000-07-25 Brent Welch	<welch@ajubasolutions.com>

	* unix/Makefile.in: Need to install all the Tcl headers because
	Itcl depends on internal headers.

2000-07-25 Andreas Kupries <a.kupries@westend.com>

	* tests/iogt.test: (line 866f) New tests iogt-6.[01], highlighting
 	  buffering trouble when stacking and unstacking transformations.
	  iogt-6.0 is solved, see the changes below. iogt-6.1 remains, for
 	  now, due to the perceived complexity of solutions.

	* generic/tclIO.h: (line 139f) struct Channel, added a buffer
	  queue, to hold data pushed back when stacking a transformation.

	* generic/tclIO.c:
	  (line 91f, line 7434f) New internal function 'CopyBuffer'.
	  Derived from 'CopyAndTranslateBuffer', with translation
	  removed.
	  (line 1025f, line 1212f): Initialization of new queue.
	  (line 1164f, Tcl_StackChannel): Pushback of input queue.
	  (line 1293f, Tcl_UnstackChannel): Discard input and pushback.
	  (line 3748f, Tcl_ReadRaw): Modified to use data in the push back
	  area before going to the driver. Uses 'CopyBuffer', s.a.
	  (line 4702f, GetInput): Modified to use data in the push back
	  area before going to the driver.
 	  (line 4867f, Tcl_Seek): Modified to take pushback of the topmost
	  channel in a stack into account.
	  (line 5620f, Tcl_InputBuffered): See above. Added
	  'Tcl_ChannelBuffered'. Analogue to 'Tcl_InputBuffered' but for
	  the buffer area in the channel.

	* generic/tcl.decls: New public API 'Tcl_ChannelBuffered'. S.a.

2000-07-19  Jeff Hobbs  <hobbs@scriptics.com>

	* tests/socket.test: removed doTestsWithRemoteServer constraint
	from socket-12.*.  It requires 'exec', not a remote server.
	Cleaned up some coding errors.

2000-07-18 Brent Welch	<welch@ajubasolutions.com>

	* win/Makefile.in: Added rules for static tcldde and tclreg libraries.

2000-07-17  Jeff Hobbs  <hobbs@scriptics.com>

	* README:
	* win/README:
	* win/README.binary:
	* win/configure.in:
	* unix/configure.in:
	* unix/tcl.spec:
	* tools/tcl.wse.in:
	* generic/tcl.h (TCL_RELEASE_SERIAL): updated to patchlevel 8.3.2

	* unix/Makefile.in:
	* win/Makefile.in:
	* win/makefile.vc: added tclIOGT.c to objects list to compile.

	* generic/tclStubInit.c:
	* generic/tclIntDecls.h:
	* generic/tclInt.decls: commented out internal decls for
	TclTestChannelCmd and TclTestChannelEventCmd as they were moved to
	tclTest.c.  Added new decls for TclChannelEventScriptInvoker and
	TclChannelTransform.

	* generic/tclIO.h: new file that contains the main internal
	structures of Tcl_Channel code to allow for multiple files to
	access them.
	* generic/tclTest.c:
	* generic/tclIO.c: broke into 3 files - tclIO.c core code, tclIO.h
	header code, and tclIOGT.c - the giot test code from Kupries.  The
	channel test code also moved to tclTest.c.
	* generic/tclIO.c (CloseChannel): stopped masking out of the
	TCL_READABLE|TCL_WRITABLE bits from the state flags in
	CloseChannel, instead adding extra intelligence to
	CheckChannelErrors with a new CHANNEL_RAW_MODE bit for special
	behavior when called from Raw channel APIs.

2000-07-13  Jeff Hobbs  <hobbs@scriptics.com>

	* generic/tclIO.c (StackSetBlockMode): moved set of chanPtr
	outside of blockModeProc check to avoid infinite loop when
	blockModeProc was NULL (Kupries).  updated TransformSeekProc to
	not call Tcl_Seek directly (Kupries).

	* win/tclWinChan.c: updated fileChannelType to v2 channel struct
	* win/tclWinConsole.c: updated consoleChannelType to v2 channel struct
	* win/tclWinPipe.c: updated pipeChannelType to v2 channel struct
	* win/tclWinSerial.c: updated serialChannelType to v2 channel struct
	* win/tclWinSock.c: updated tcpChannelType to v2 channel struct

2000-07-11  Brent Welch	<welch@ajubasolutions.com>

	* win/tclConfig.sh.in: Cleaned up unix-specific autoconf variables.

2000-07-11  Jeff Hobbs  <hobbs@scriptics.com>

	* tests/iogt.test: made tests [345].0 not run by default as they
	were failing in the new design, but I'm not convinced that the
	returned result isn't correct.

	* generic/tclDecls.h:
	* generic/tclStubInit.c:
	* generic/tcl.decls: added Tcl_GetTopChannel C API that returns
	the current top channel of a channel stack.  Tcl_GetChannel was
	changed earlier to return the bottommost channel of a stack
	because that is the one that is guaranteed to stay around the
	longest, and this was needed to compensate for certain
	operations that want to look at the state of the main channel.
	Most channel APIs already compensate for grabbing the top, so it
	shouldn't be needed often.

	* generic/tclIO.c (Tcl_StackChannel, Tcl_UnstackChannel): Added
	flushing of buffers (Kupries), removed use of DownChannel macro,
	added Tcl_GetTopChannel public API to get to the top channel of
	the channel stack (necessary for TLS).  Rewrote Tcl_NotifyChannel
	for new channel design (Kupries).  Did some code cleanup in the
	transform code.  tclIO.c must still be broken into bits (separate
	out test code and giot code, create tclIO.h).

2000-07-10  Andreas Kupries <a.kupries@westend.com>

	* tests/iogt.test: Reverted some earlier changes as a fix by Jeff
	  revived the original and correct behaviour. IOW, the tests showed
	  a genuine error and I didn't see it :(.

	* generic/tclIO.c (Tcl_Read|Write_Raw): Changed to directly use
 	  the drivers and not DoRead|DoWrite. The latter use the buffering
 	  system, encoding and eol-translation and this wreaks havoc with
 	  the data going through the transformations. Both procedures use
 	  CheckForchannelErrors and let it believe that there is no
 	  background copy in progress or else stacked channels could not
	  be used for that.

	* generic/tclIO.c (TclCopyChannel, CopyData): Moved access to the
 	  topmost channel from the first to the second procedure to make
 	  the decision about that at the last possible time (Callbacks can
 	  change the stacking).

	test suite: failures of iogt-[345].0
	
2000-07-06  Jeff Hobbs  <hobbs@scriptics.com>

	* tests/iogt.test: new tests for stacked channel stuff based off
	new 'testchannel transform|unstack' code (Kupries IOGT extension).
	* generic/tcl.decls:
	* generic/tcl.h:
	* generic/tclDecls.h:
	* generic/tclStubsInit.c:
	* generic/tclIO.c (TclCopyChannel): complete rewrite of Tcl
	Channel code for stacked channels.  HOBBS: ADD MORE WHEN DONE.

2000-06-02  Jeff Hobbs  <hobbs@scriptics.com>

	* generic/tclIO.c (CloseChannel): removed the &ing out of
	(TCL_READABLE|TCL_WRITABLE) from the flags, as CloseChannel does
	this on the next pass through for the top channel, and it appeared
	to be causing hangs by not allowing the final flush.

README:  Tcl
    This is the Tcl 8.3.1 source distribution.
    This is the Tcl 8.3.2 source distribution.
    You can get any release of Tcl from:
        http://dev.scriptics.com/registration/<version>.tml
    Tcl/Tk is also available through NetCVS:
	http://dev.scriptics.com/software/tcltk/netcvs.html

RCS: @(#) $Id: README,v 1.31 2000/04/26 17:31:19 hobbs Exp $
RCS: @(#) $Id: README,v 1.31.4.1 2000/07/17 23:09:53 hobbs Exp $

Contents
--------
    1. Introduction
    2. Documentation
    3. Compiling and installing Tcl
    4. Development tools

---------------

Extensive documentation is available at our website.
The home page for this release, including new features, is
	http://dev.scriptics.com/software/tcltk/8.3.html

Detailed release notes can be found at
	http://dev.scriptics.com/software/tcltk/relnotes/tcl8.3.1.txt
	http://dev.scriptics.com/software/tcltk/relnotes/tcl8.3.2.txt

Information about Tcl itself can be found at
	http://dev.scriptics.com/scripting/

There are many Tcl books on the market.  Most are listed at
	http://dev.scriptics.com/resource/doc/books/

'\"
'\" Copyright (c) 1992-1999 Karl Lehenbauer and Mark Diekhans.
'\" Copyright (c) 2000 by Scriptics Corporation.
'\" All rights reserved.
'\" 
'\" RCS: @(#) $Id: DumpActiveMemory.3,v 1.2 2000/04/28 00:47:48 ericm Exp $
'\" 
.so man.macros
.TH "Tcl_DumpActiveMemory" 3 8.1 Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_DumpActiveMemory, Tcl_InitMemory, Tcl_ValidateAllMemory \- Validated memory allocation interface.
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
int
\fBTcl_DumpActiveMemory\fR(\fIfileName\fR)
.sp
void
\fBTcl_InitMemory\fR(\fIinterp\fR)
.sp
void
\fBTcl_ValidateAllMemory\fR(\fIfileName, line\fR)

.SH ARGUMENTS
.AP Tcl_Interp *interp in
Tcl interpreter in which to add commands.
.AP char *fileName in
For \fBTcl_DumpActiveMemory\fR, name of the file to which memory
information will be written.  For \fBTcl_ValidateAllMemory\fR, name of
the file from which the call is being made (normally \fB__FILE__\fR).
.AP int line in
Line number at which the call to \fBTcl_ValidateAllMemory\fR is made
(normally \fB__LINE__\fR).
.BE

.SH DESCRIPTION
These functions provide access to Tcl memory debugging information.
They are only available when Tcl has been compiled with
\fBTCL_MEM_DEBUG\fR defined at compile-time.
.PP 
\fBTcl_DumpActiveMemory\fR will output a list of all currently
allocated memory to the specified file.  The information output for
each allocated block of memory is:  starting and ending addresses
(excluding guard zone), size, source file where \fBckalloc\fR was
called to allocate the block and line number in that file.  It is
especially useful to call \fBTcl_DumpActiveMemory\fR after the Tcl
interpreter has been deleted.
.PP
\fBTcl_InitMemory\fR adds the Tcl \fBmemory\fR command to the
interpreter given by \fIinterp\fR.  It is called by \fBTcl_Main\fR
when Tcl has been compiled with \fBTCL_MEM_DEBUG\fR defined.
.PP
\fBTcl_ValidateAllMemory\fR forces a validation of the guard zones of
all currently allocated blocks of memory.  Normally validation of a
block occurs when its freed, unless full validation is enabled, in
which case validation of all blocks occurs when \fBckalloc\fR and
\fBckfree\fR are called.  This function forces the validation to occur
at any point.

.SH "SEE ALSO"
TCL_MEM_DEBUG, memory

.SH KEYWORDS
memory, debug

'\"
'\" Copyright (c) 1998-2000 by Scriptics Corporation.
'\" All rights reserved.
'\" 
'\" RCS: @(#) $Id: Init.3,v 1.1 2000/04/28 00:47:48 ericm Exp $
'\" 
.so man.macros
.TH Tcl_Init 3 8.0 Tcl "Tcl Library Procedures"
.BS
.SH NAME
Tcl_Init \- find and source initialization script
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
int
\fBTcl_Init\fR(\fIinterp\fR)
.SH ARGUMENTS
.AP Tcl_Interp *interp in
Interpreter to initialize.
.BE

.SH DESCRIPTION
.PP
\fBTcl_Init\fR is a helper procedure that finds and \fBsource\fR's the
\fBinit.tcl\fR script, which should exist somewhere on the Tcl library
path.  On Macintosh systems, it additionally checks for an \fBInit\fR
resource and sources the contents of that resource if \fBinit.tcl\fR
cannot be found.
.PP
\fBTcl_Init\fR is typically called from \fBTcl_AppInit\fR procedures.

.SH "SEE ALSO"
Tcl_AppInit, Tcl_Main

.SH KEYWORDS
application, initialization, interpreter

'\" 
'\" Copyright (c) 1992-1999 Karl Lehenbauer and Mark Diekhans.
'\" Copyright (c) 2000 by Scriptics Corporation.
'\" All rights reserved.
'\" 
'\" RCS: @(#) $Id: TCL_MEM_DEBUG.3,v 1.2 2000/04/28 00:47:49 ericm Exp $
'\" 
.so man.macros
.TH TCL_MEM_DEBUG 3 8.1 Tcl "Tcl Library Procedures"
.BS
.SH NAME
TCL_MEM_DEBUG \- Compile-time flag to enable Tcl memory debugging.

.SH DESCRIPTION
When Tcl is compiled with \fBTCL_MEM_DEBUG\fR defined, a powerful set
of memory debugging aids are included in the compiled binary.  This
includes C and Tcl functions which can aid with debugging
memory leaks, memory allocation overruns, and other memory related
errors.

.SH ENABLING MEMORY DEBUGGING
.PP
To enable memory debugging, Tcl should be recompiled from scratch with
\fBTCL_MEM_DEBUG\fR defined.  This will also compile in a non-stub
version of \fBTcl_InitMemory\fR to add the \fBmemory\fR command to Tcl.
.PP
\fBTCL_MEM_DEBUG\fR must be either left defined for all modules or undefined
for all modules that are going to be linked together.  If they are not, link
errors will occur, with either \fBTclDbCkfree\fR and \fBTcl_DbCkalloc\fR or
\fBTcl_Ckalloc\fR and \fBTcl_Ckfree\fR being undefined.
.PP
Once memory debugging support has been compiled into Tcl, the C
functions \fBTcl_ValidateAllMemory\fR, and \fBTcl_DumpActiveMemory\fR,
and the Tcl \fBmemory\fR command can be used to validate and examine
memory usage.

.SH GUARD ZONES
.PP
When memory debugging is enabled, whenever a call to \fBckalloc\fR is
made, slightly more memory than requested is allocated so the memory debugging
code can keep track of the allocated memory, and eight-byte ``guard
zones'' are placed in front of and behind the space that will be
returned to the caller.  (The size of the guard zone is defined by the
C #define \fBGUARD_SIZE\fR in \fIbaseline/src/ckalloc.c\fR -- it can
be extended if you suspect large overwrite problems, at some cost in
performance.)  A known pattern is written into the guard zones and, on
a call to \fBckfree\fR, the guard zones of the space being freed are
checked to see if either zone has been modified in any way.  If one
has been, the guard bytes and their new contents are identified, and a
``low guard failed'' or ``high guard failed'' message is issued.  The
``guard failed'' message includes the address of the memory packet and
the file name and line number of the code that called \fBckfree\fR.
This allows you to detect the common sorts of one-off problems, where
not enough space was allocated to contain the data written, for
example.

.SH DEBUGGING DIFFICULT MEMORY CORRUPTION PROBLEMS
.PP
Normally, Tcl compiled with memory debugging enabled will make it easy
to isolate a corruption problem.  Turning on memory validation with
the memory command can help isolate difficult problems.  If you
suspect (or know) that corruption is occurring before the Tcl
interpreter comes up far enough for you to issue commands, you can set
\fBMEM_VALIDATE\fR define, recompile tclCkalloc.c and rebuild Tcl.
This will enable memory validation from the first call to
\fBckalloc\fR, again, at a large performance impact.
.PP
If you are desperate and validating memory on every call to
\fBckalloc\fR and \fBckfree\fR isn't enough, you can explicitly call
\fBTcl_ValidateAllMemory\fR directly at any point.  It takes a \fIchar
*\fR and an \fIint\fR which are normally the filename and line number
of the caller, but they can actually be anything you want.  Remember
to remove the calls after you find the problem.

.SH "SEE ALSO"
memory, Tcl_ValidateAllMemory, Tcl_DumpActiveMemory

.SH KEYWORDS
memory, debug

'\"
'\" Copyright (c) 1992-1999 by Karl Lehenbauer and Mark Diekhans
'\" Copyright (c) 2000 by Scriptics Corporation.
'\" All rights reserved.
'\" 
'\" RCS: @(#) $Id: memory.n,v 1.2 2000/04/28 00:47:49 ericm Exp $
'\" 
.so man.macros
.TH memory n 8.1 Tcl "Tcl Built-In Commands"
.BS
.SH NAME
memory \- Control Tcl memory debugging capabilities.
.SH SYNOPSIS
\fBmemory \fIoption \fR?\fIarg arg ...\fR?

.SH DESCRIPTION
.PP
The \fBmemory\fR command gives the Tcl developer control of Tcl's memory
debugging capabilities.  The memory command has several suboptions, which are
described below.  It is only available when Tcl has been compiled with
memory debugging enabled (when \fBTCL_MEM_DEBUG\fR is defined at
compile time).
.TP
\fBmemory info\fR
Produces a report containing the total allocations and frees since 
Tcl began, the current packets allocated (the current
number of calls to \fBckalloc\fR not met by a corresponding call 
to \fBckfree\fR), the current bytes allocated, and the maximum number
of packets and bytes allocated.
.TP
\fBmemory trace [on|off]\fR
.br
Turns memory tracing on or off.  When memory tracing is on, every call
to \fBckalloc\fR causes a line of trace information to be written to
\fIstderr\fR, consisting of the word \fIckalloc\fR, followed by the
address returned, the amount of memory allocated, and the C filename
and line number of the code performing the allocation.  For example:
.CS
ckalloc 40e478 98 tclProc.c 1406
.CE
Calls to \fBckfree\fR are traced in the same manner.
.TP
\fBmemory validate [on|off]\fR
Turns memory validation on or off. When memory validation is enabled,
on every call to \fBckalloc\fR or \fBckfree\fR, the guard zones are
checked for every piece of memory currently in existence that was
allocated by \fBckalloc\fR.  This has a large performance impact and
should only be used when overwrite problems are strongly suspected.
The advantage of enabling memory validation is that a guard zone
overwrite can be detected on the first call to \fBckalloc\fR or
\fBckfree\fR after the overwrite occurred, rather than when the
specific memory with the overwritten guard zone(s) is freed, which may
occur long after the overwrite occurred.
.TP
\fBmemory trace_on_at_malloc\fR \fIcount\fR
Enable memory tracing after \fIcount\fR \fBckalloc\fR's have been performed.
For example, if you enter \fBmemory trace_on_at_malloc 100\fR,
after the 100th call to \fBckalloc\fR, memory trace information will begin
being displayed for all allocations and frees.  Since there can be a lot
of memory activity before a problem occurs, judicious use of this option
can reduce the slowdown caused by tracing (and the amount of trace information
produced), if you can identify a number of allocations that occur before
the problem sets in.  The current number of memory allocations that have 
occurred since Tcl started is printed on a guard zone failure.
.TP
\fBmemory break_on_malloc\fR \fIcount\fR
After the \fBcount\fR allocations have been performed, \fBckalloc\fR's
output a message to this effect and that it is now attempting to enter
the C debugger.  Tcl will then issue a \fISIGINT\fR signal against itself.
If you are running Tcl under a C debugger, it should then enter the debugger
command mode.
.TP
\fB memory display\fR \fIfile\fR
Write a list of all currently allocated memory to the specified file.

.SH "SEE ALSO"
ckalloc, ckfree, Tcl_ValidateAllMemory, Tcl_DumpActiveMemory, TCL_MEM_DEBUG

.SH KEYWORDS
memory, debug

# tcl.decls --
#
#	This file contains the declarations for all supported public
#	functions that are exported by the Tcl library via the stubs table.
#	This file is used to generate the tclDecls.h, tclPlatDecls.h,
#	tclStub.c, and tclPlatStub.c files.
#	
#
# Copyright (c) 1998-1999 by Scriptics Corporation.
# See the file "license.terms" for information on usage and redistribution
# of this file, and for a DISCLAIMER OF ALL WARRANTIES.
# 
# RCS: @(#) $Id: tcl.decls,v 1.33 2000/04/09 16:04:17 kupries Exp $
# RCS: @(#) $Id: tcl.decls,v 1.33.4.3 2000/07/25 16:54:47 kupries Exp $

library tcl

# Define the tcl interface with several sub interfaces:
#     tclPlat	 - platform specific public
#     tclInt	 - generic private
#     tclPlatInt - platform specific private

declare 281 generic {
    Tcl_Channel Tcl_StackChannel(Tcl_Interp *interp, \
	    Tcl_ChannelType *typePtr, ClientData instanceData, \
	    int mask, Tcl_Channel prevChan)
}
declare 282 generic {
    void Tcl_UnstackChannel(Tcl_Interp *interp, Tcl_Channel chan)
    int Tcl_UnstackChannel(Tcl_Interp *interp, Tcl_Channel chan)
}
declare 283 generic {
    Tcl_Channel Tcl_GetStackedChannel(Tcl_Channel chan)
}
# Reserved for future use (8.0.x vs. 8.1)
#  declare 284 generic {
#  }

declare 392 generic {
    void Tcl_MutexFinalize (Tcl_Mutex *mutex)
}
declare 393 generic {
    int Tcl_CreateThread (Tcl_ThreadId *idPtr, Tcl_ThreadCreateProc proc, \
	    ClientData clientData, int stackSize, int flags)
}

declare 394 generic {
    int Tcl_ReadRaw (Tcl_Channel chan, char *dst, int bytesToRead)
}
declare 395 generic {
    int Tcl_WriteRaw (Tcl_Channel chan, char *src, int srcLen)
}
declare 396 generic {
    Tcl_Channel Tcl_GetTopChannel (Tcl_Channel chan)
}
declare 397 generic {
    int Tcl_ChannelBuffered (Tcl_Channel chan)
}

##############################################################################

# Define the platform specific public Tcl interface.  These functions are
# only available on the designated platform.

interface tclPlat

 * Copyright (c) 1993-1996 Lucent Technologies.
 * Copyright (c) 1994-1998 Sun Microsystems, Inc.
 * Copyright (c) 1998-2000 by Scriptics Corporation.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tcl.h,v 1.70 2000/04/19 08:32:44 hobbs Exp $
 * RCS: @(#) $Id: tcl.h,v 1.70.4.2 2000/07/17 23:09:54 hobbs Exp $
 */

#ifndef _TCL
#define _TCL

/*
 * For C++ compilers, use extern "C"

 * tools/tcl.wse.in	(for windows installer)
 * tools/tclSplash.bmp	(not patchlevel)
 */

#define TCL_MAJOR_VERSION   8
#define TCL_MINOR_VERSION   3
#define TCL_RELEASE_LEVEL   TCL_FINAL_RELEASE
#define TCL_RELEASE_SERIAL  1
#define TCL_RELEASE_SERIAL  2

#define TCL_VERSION	    "8.3"
#define TCL_PATCH_LEVEL	    "8.3.1"
#define TCL_PATCH_LEVEL	    "8.3.2"

/*
 * The following definitions set up the proper options for Windows
 * compilers.  We use this method because there is no autoconf equivalent.
 */

#ifndef __WIN32__

typedef struct Tcl_Pid_ *Tcl_Pid;
typedef struct Tcl_RegExp_ *Tcl_RegExp;
typedef struct Tcl_ThreadDataKey_ *Tcl_ThreadDataKey;
typedef struct Tcl_ThreadId_ *Tcl_ThreadId;
typedef struct Tcl_TimerToken_ *Tcl_TimerToken;
typedef struct Tcl_Trace_ *Tcl_Trace;
typedef struct Tcl_Var_ *Tcl_Var;
typedef struct Tcl_ChannelVersion_ *Tcl_ChannelVersion;

/*
 * Definition of the interface to procedures implementing threads.
 * A procedure following this definition is given to each call of
 * 'Tcl_CreateThread' and will be called as the main fuction of
 * the new thread created by that call.
 */

/*
 * Bits passed to Tcl_DriverClose2Proc to indicate which side of a channel
 * should be closed.
 */

#define TCL_CLOSE_READ		(1<<1)
#define TCL_CLOSE_WRITE	(1<<2)
#define TCL_CLOSE_WRITE		(1<<2)

/*
 * Value to use as the closeProc for a channel that supports the
 * close2Proc interface.
 */

#define TCL_CLOSE2PROC	((Tcl_DriverCloseProc *)1)

/*
 * Channel version tag.  This was introduced in 8.3.2/8.4.
 */

#define TCL_CHANNEL_VERSION_1	((Tcl_ChannelVersion) 0x1)
#define TCL_CHANNEL_VERSION_2	((Tcl_ChannelVersion) 0x2)

/*
 * Typedefs for the various operations in a channel type:
 */

typedef int	(Tcl_DriverBlockModeProc) _ANSI_ARGS_((
		    ClientData instanceData, int mode));
typedef int	(Tcl_DriverCloseProc) _ANSI_ARGS_((ClientData instanceData,

		    ClientData instanceData, Tcl_Interp *interp,
		    char *optionName, Tcl_DString *dsPtr));
typedef void	(Tcl_DriverWatchProc) _ANSI_ARGS_((
		    ClientData instanceData, int mask));
typedef int	(Tcl_DriverGetHandleProc) _ANSI_ARGS_((
		    ClientData instanceData, int direction,
		    ClientData *handlePtr));
typedef int	(Tcl_DriverFlushProc) _ANSI_ARGS_((
		    ClientData instanceData));
typedef int	(Tcl_DriverHandlerProc) _ANSI_ARGS_((
		    ClientData instanceData, int interestMask));

/*
 * The following declarations either map ckalloc and ckfree to
 * malloc and free, or they map them to procedures with all sorts
 * of debugging hooks defined in tclCkalloc.c.
 */

 * One such structure exists for each type (kind) of channel.
 * It collects together in one place all the functions that are
 * part of the specific channel type.
 */

typedef struct Tcl_ChannelType {
    char *typeName;			/* The name of the channel type in Tcl
                                         * commands. This storage is owned by
                                         * channel type. */
					 * commands. This storage is owned by
					 * channel type. */
    Tcl_DriverBlockModeProc *blockModeProc;
    					/* Set blocking mode for the
                                         * raw channel. May be NULL. */
    Tcl_ChannelVersion version;		/* Version of the channel. */
    Tcl_DriverCloseProc *closeProc;	/* Procedure to call to close the
                                         * channel, or TCL_CLOSE2PROC if the
                                         * close2Proc should be used
                                         * instead. */
					 * channel, or TCL_CLOSE2PROC if the
					 * close2Proc should be used
					 * instead. */
    Tcl_DriverInputProc *inputProc;	/* Procedure to call for input
                                         * on channel. */
					 * on channel. */
    Tcl_DriverOutputProc *outputProc;	/* Procedure to call for output
                                         * on channel. */
					 * on channel. */
    Tcl_DriverSeekProc *seekProc;	/* Procedure to call to seek
                                         * on the channel. May be NULL. */
					 * on the channel. May be NULL. */
    Tcl_DriverSetOptionProc *setOptionProc;
    					/* Set an option on a channel. */
					/* Set an option on a channel. */
    Tcl_DriverGetOptionProc *getOptionProc;
    					/* Get an option from a channel. */
					/* Get an option from a channel. */
    Tcl_DriverWatchProc *watchProc;	/* Set up the notifier to watch
                                         * for events on this channel. */
					 * for events on this channel. */
    Tcl_DriverGetHandleProc *getHandleProc;
					/* Get an OS handle from the channel
                                         * or NULL if not supported. */
    Tcl_DriverClose2Proc *close2Proc;   /* Procedure to call to close the
					 * or NULL if not supported. */
    Tcl_DriverClose2Proc *close2Proc;	/* Procedure to call to close the
					 * channel if the device supports
					 * closing the read & write sides
					 * independently. */
    Tcl_DriverBlockModeProc *blockModeProc;
					/* Set blocking mode for the
					 * raw channel. May be NULL. */
    /*
     * Only valid in TCL_CHANNEL_VERSION_2 channels
     */
    Tcl_DriverFlushProc *flushProc;	/* Procedure to call to flush a
					 * channel. May be NULL. */
    Tcl_DriverHandlerProc *handlerProc;	/* Procedure to call to handle a
					 * channel event.  This will be passed
					 * up the stacked channel chain. */
} Tcl_ChannelType;

/*
 * The following macros are provided as convenience functions
 * for accessing the internals of the Tcl_ChannelType
 */

#define Tcl_ChannelName(chanTypePtr)		((chanTypePtr)->typeName)
#define Tcl_ChannelVersion(chanTypePtr) \
	(((chanTypePtr)->version == TCL_CHANNEL_VERSION_2) ? \
		TCL_CHANNEL_VERSION_2 : TCL_CHANNEL_VERSION_1)
#define Tcl_ChannelBlockModeProc(chanTypePtr) \
	(((chanTypePtr)->version == TCL_CHANNEL_VERSION_2) ? \
		(chanTypePtr)->blockModeProc : \
		(Tcl_DriverBlockModeProc *) (chanTypePtr)->version)
#define Tcl_ChannelCloseProc(chanTypePtr)	((chanTypePtr)->closeProc)
#define Tcl_ChannelClose2Proc(chanTypePtr)	((chanTypePtr)->close2Proc)
#define Tcl_ChannelInputProc(chanTypePtr)	((chanTypePtr)->inputProc)
#define Tcl_ChannelOutputProc(chanTypePtr)	((chanTypePtr)->outputProc)
#define Tcl_ChannelSeekProc(chanTypePtr)	((chanTypePtr)->seekProc)
#define Tcl_ChannelSetOptionProc(chanTypePtr)	((chanTypePtr)->setOptionProc)
#define Tcl_ChannelGetOptionProc(chanTypePtr)	((chanTypePtr)->getOptionProc)
#define Tcl_ChannelWatchProc(chanTypePtr)	((chanTypePtr)->watchProc)
#define Tcl_ChannelGetHandleProc(chanTypePtr)	((chanTypePtr)->getHandleProc)
#define Tcl_ChannelFlushProc(chanTypePtr)	((chanTypePtr)->flushProc)
#define Tcl_ChannelHandlerProc(chanTypePtr)	((chanTypePtr)->handlerProc)

/*
 * The following flags determine whether the blockModeProc above should
 * set the channel into blocking or nonblocking mode. They are passed
 * as arguments to the blockModeProc procedure in the above structure.
 */

#define TCL_MODE_BLOCKING 0		/* Put channel into blocking mode. */
#define TCL_MODE_NONBLOCKING 1		/* Put channel into nonblocking
#define TCL_MODE_BLOCKING	0	/* Put channel into blocking mode. */
#define TCL_MODE_NONBLOCKING	1	/* Put channel into nonblocking
					 * mode. */

/*
 * Enum for different types of file paths.
 */

typedef enum Tcl_PathType {

/*
 * tclDecls.h --
 *
 *	Declarations of functions in the platform independent public Tcl API.
 *
 * Copyright (c) 1998-1999 by Scriptics Corporation.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclDecls.h,v 1.34 2000/04/09 16:04:17 kupries Exp $
 * RCS: @(#) $Id: tclDecls.h,v 1.34.4.3 2000/07/25 16:54:48 kupries Exp $
 */

#ifndef _TCLDECLS
#define _TCLDECLS

/*
 * WARNING: This file is automatically generated by the tools/genStubs.tcl

EXTERN void		Tcl_InitMemory _ANSI_ARGS_((Tcl_Interp * interp));
/* 281 */
EXTERN Tcl_Channel	Tcl_StackChannel _ANSI_ARGS_((Tcl_Interp * interp, 
				Tcl_ChannelType * typePtr, 
				ClientData instanceData, int mask, 
				Tcl_Channel prevChan));
/* 282 */
EXTERN void		Tcl_UnstackChannel _ANSI_ARGS_((Tcl_Interp * interp, 
EXTERN int		Tcl_UnstackChannel _ANSI_ARGS_((Tcl_Interp * interp, 
				Tcl_Channel chan));
/* 283 */
EXTERN Tcl_Channel	Tcl_GetStackedChannel _ANSI_ARGS_((Tcl_Channel chan));
/* Slot 284 is reserved */
/* Slot 285 is reserved */
/* 286 */
EXTERN void		Tcl_AppendObjToObj _ANSI_ARGS_((Tcl_Obj * objPtr, 

/* 392 */
EXTERN void		Tcl_MutexFinalize _ANSI_ARGS_((Tcl_Mutex * mutex));
/* 393 */
EXTERN int		Tcl_CreateThread _ANSI_ARGS_((Tcl_ThreadId * idPtr, 
				Tcl_ThreadCreateProc proc, 
				ClientData clientData, int stackSize, 
				int flags));
/* 394 */
EXTERN int		Tcl_ReadRaw _ANSI_ARGS_((Tcl_Channel chan, 
				char * dst, int bytesToRead));
/* 395 */
EXTERN int		Tcl_WriteRaw _ANSI_ARGS_((Tcl_Channel chan, 
				char * src, int srcLen));
/* 396 */
EXTERN Tcl_Channel	Tcl_GetTopChannel _ANSI_ARGS_((Tcl_Channel chan));
/* 397 */
EXTERN int		Tcl_ChannelBuffered _ANSI_ARGS_((Tcl_Channel chan));

typedef struct TclStubHooks {
    struct TclPlatStubs *tclPlatStubs;
    struct TclIntStubs *tclIntStubs;
    struct TclIntPlatStubs *tclIntPlatStubs;
} TclStubHooks;

#endif /* __WIN32__ */
#ifdef MAC_TCL
    void *reserved278;
#endif /* MAC_TCL */
    void (*tcl_GetVersion) _ANSI_ARGS_((int * major, int * minor, int * patchLevel, int * type)); /* 279 */
    void (*tcl_InitMemory) _ANSI_ARGS_((Tcl_Interp * interp)); /* 280 */
    Tcl_Channel (*tcl_StackChannel) _ANSI_ARGS_((Tcl_Interp * interp, Tcl_ChannelType * typePtr, ClientData instanceData, int mask, Tcl_Channel prevChan)); /* 281 */
    void (*tcl_UnstackChannel) _ANSI_ARGS_((Tcl_Interp * interp, Tcl_Channel chan)); /* 282 */
    int (*tcl_UnstackChannel) _ANSI_ARGS_((Tcl_Interp * interp, Tcl_Channel chan)); /* 282 */
    Tcl_Channel (*tcl_GetStackedChannel) _ANSI_ARGS_((Tcl_Channel chan)); /* 283 */
    void *reserved284;
    void *reserved285;
    void (*tcl_AppendObjToObj) _ANSI_ARGS_((Tcl_Obj * objPtr, Tcl_Obj * appendObjPtr)); /* 286 */
    Tcl_Encoding (*tcl_CreateEncoding) _ANSI_ARGS_((Tcl_EncodingType * typePtr)); /* 287 */
    void (*tcl_CreateThreadExitHandler) _ANSI_ARGS_((Tcl_ExitProc * proc, ClientData clientData)); /* 288 */
    void (*tcl_DeleteThreadExitHandler) _ANSI_ARGS_((Tcl_ExitProc * proc, ClientData clientData)); /* 289 */

    Tcl_Mutex * (*tcl_GetAllocMutex) _ANSI_ARGS_((void)); /* 387 */
    int (*tcl_GetChannelNames) _ANSI_ARGS_((Tcl_Interp * interp)); /* 388 */
    int (*tcl_GetChannelNamesEx) _ANSI_ARGS_((Tcl_Interp * interp, char * pattern)); /* 389 */
    int (*tcl_ProcObjCmd) _ANSI_ARGS_((ClientData clientData, Tcl_Interp * interp, int objc, Tcl_Obj *CONST objv[])); /* 390 */
    void (*tcl_ConditionFinalize) _ANSI_ARGS_((Tcl_Condition * condPtr)); /* 391 */
    void (*tcl_MutexFinalize) _ANSI_ARGS_((Tcl_Mutex * mutex)); /* 392 */
    int (*tcl_CreateThread) _ANSI_ARGS_((Tcl_ThreadId * idPtr, Tcl_ThreadCreateProc proc, ClientData clientData, int stackSize, int flags)); /* 393 */
    int (*tcl_ReadRaw) _ANSI_ARGS_((Tcl_Channel chan, char * dst, int bytesToRead)); /* 394 */
    int (*tcl_WriteRaw) _ANSI_ARGS_((Tcl_Channel chan, char * src, int srcLen)); /* 395 */
    Tcl_Channel (*tcl_GetTopChannel) _ANSI_ARGS_((Tcl_Channel chan)); /* 396 */
    int (*tcl_ChannelBuffered) _ANSI_ARGS_((Tcl_Channel chan)); /* 397 */
} TclStubs;

#ifdef __cplusplus
extern "C" {
#endif
extern TclStubs *tclStubsPtr;
#ifdef __cplusplus

#define Tcl_MutexFinalize \
	(tclStubsPtr->tcl_MutexFinalize) /* 392 */
#endif
#ifndef Tcl_CreateThread
#define Tcl_CreateThread \
	(tclStubsPtr->tcl_CreateThread) /* 393 */
#endif
#ifndef Tcl_ReadRaw
#define Tcl_ReadRaw \
	(tclStubsPtr->tcl_ReadRaw) /* 394 */
#endif
#ifndef Tcl_WriteRaw
#define Tcl_WriteRaw \
	(tclStubsPtr->tcl_WriteRaw) /* 395 */
#endif
#ifndef Tcl_GetTopChannel
#define Tcl_GetTopChannel \
	(tclStubsPtr->tcl_GetTopChannel) /* 396 */
#endif
#ifndef Tcl_ChannelBuffered
#define Tcl_ChannelBuffered \
	(tclStubsPtr->tcl_ChannelBuffered) /* 397 */
#endif

#endif /* defined(USE_TCL_STUBS) && !defined(USE_TCL_STUB_PROCS) */

/* !END!: Do not edit above this line. */

#endif /* _TCLDECLS */

/* 
 * tclIO.c --
 *
 *	This file provides the generic portions (those that are the same on
 *	all platforms and for all channel types) of Tcl's IO facilities.
 *
 * Copyright (c) 1998 Scriptics Corporation
 * Copyright (c) 1998-2000 Ajuba Solutions
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclIO.c,v 1.20.2.3 2000/06/02 20:04:06 hobbs Exp $
 * RCS: @(#) $Id: tclIO.c,v 1.20.2.3.2.6 2000/07/25 16:54:49 kupries Exp $
 */

#include "tclInt.h"
#include "tclPort.h"

#include "tclIO.h"
/*
 * Make sure that both EAGAIN and EWOULDBLOCK are defined. This does not
 * compile on systems where neither is defined. We want both defined so
 * that we can test safely for both. In the code we still have to test for
 * both because there may be systems on which both are defined and have
 * different values.
 */

#if ((!defined(EWOULDBLOCK)) && (defined(EAGAIN)))
#   define EWOULDBLOCK EAGAIN
#endif
#if ((!defined(EAGAIN)) && (defined(EWOULDBLOCK)))
#   define EAGAIN EWOULDBLOCK
#endif
#if ((!defined(EAGAIN)) && (!defined(EWOULDBLOCK)))
error one of EWOULDBLOCK or EAGAIN must be defined
#endif


/*
 * The following structure encapsulates the state for a background channel
 * copy.  Note that the data buffer for the copy will be appended to this
 * structure.
 */

typedef struct CopyState {
    struct Channel *readPtr;	/* Pointer to input channel. */
    struct Channel *writePtr;	/* Pointer to output channel. */
    int readFlags;		/* Original read channel flags. */
    int writeFlags;		/* Original write channel flags. */
    int toRead;			/* Number of bytes to copy, or -1. */
    int total;			/* Total bytes transferred (written). */
    Tcl_Interp *interp;		/* Interp that started the copy. */
    Tcl_Obj *cmdPtr;		/* Command to be invoked at completion. */
    int bufSize;		/* Size of appended buffer. */
    char buffer[1];		/* Copy buffer, this must be the last
				 * field. */
} CopyState;

/*
 * struct ChannelBuffer:
 *
 * Buffers data being sent to or from a channel.
 */

typedef struct ChannelBuffer {
    int nextAdded;		/* The next position into which a character
                                 * will be put in the buffer. */
    int nextRemoved;		/* Position of next byte to be removed
                                 * from the buffer. */
    int bufLength;		/* How big is the buffer? */
    struct ChannelBuffer *nextPtr;
    				/* Next buffer in chain. */
    char buf[4];		/* Placeholder for real buffer. The real
                                 * buffer occuppies this space + bufSize-4
                                 * bytes. This must be the last field in
                                 * the structure. */
} ChannelBuffer;

#define CHANNELBUFFER_HEADER_SIZE	(sizeof(ChannelBuffer) - 4)

/*
 * How much extra space to allocate in buffer to hold bytes from previous
 * buffer (when converting to UTF-8) or to hold bytes that will go to
 * next buffer (when converting from UTF-8).
 */
 
#define BUFFER_PADDING	    16
 
/*
 * The following defines the *default* buffer size for channels.
 */

#define CHANNELBUFFER_DEFAULT_SIZE	(1024 * 4)

/*
 * Structure to record a close callback. One such record exists for
 * each close callback registered for a channel.
 */

typedef struct CloseCallback {
    Tcl_CloseProc *proc;		/* The procedure to call. */
    ClientData clientData;		/* Arbitrary one-word data to pass
                                         * to the callback. */
    struct CloseCallback *nextPtr;	/* For chaining close callbacks. */
} CloseCallback;

/*
 * The following structure describes the information saved from a call to
 * "fileevent". This is used later when the event being waited for to
 * invoke the saved script in the interpreter designed in this record.
 */

typedef struct EventScriptRecord {
    struct Channel *chanPtr;	/* The channel for which this script is
                                 * registered. This is used only when an
                                 * error occurs during evaluation of the
                                 * script, to delete the handler. */
    Tcl_Obj *scriptPtr;		/* Script to invoke. */
    Tcl_Interp *interp;		/* In what interpreter to invoke script? */
    int mask;			/* Events must overlap current mask for the
                                 * stored script to be invoked. */
    struct EventScriptRecord *nextPtr;
    				/* Next in chain of records. */
} EventScriptRecord;

/*
 * struct Channel:
 *
 * One of these structures is allocated for each open channel. It contains data
 * specific to the channel but which belongs to the generic part of the Tcl
 * channel mechanism, and it points at an instance specific (and type
 * specific) * instance data, and at a channel type structure.
 */

typedef struct Channel {
    char *channelName;		/* The name of the channel instance in Tcl
                                 * commands. Storage is owned by the generic IO
                                 * code,  is dynamically allocated. */
    int	flags;			/* ORed combination of the flags defined
                                 * below. */
    Tcl_Encoding encoding;	/* Encoding to apply when reading or writing
				 * data on this channel.  NULL means no
				 * encoding is applied to data. */
    Tcl_EncodingState inputEncodingState;
				/* Current encoding state, used when converting
				 * input data bytes to UTF-8. */
    int inputEncodingFlags;	/* Encoding flags to pass to conversion
				 * routine when converting input data bytes to
				 * UTF-8.  May be TCL_ENCODING_START before
				 * converting first byte and TCL_ENCODING_END
				 * when EOF is seen. */
    Tcl_EncodingState outputEncodingState;
				/* Current encoding state, used when converting
				 * UTF-8 to output data bytes. */
    int outputEncodingFlags;	/* Encoding flags to pass to conversion
				 * routine when converting UTF-8 to output
				 * data bytes.  May be TCL_ENCODING_START
				 * before converting first byte and
				 * TCL_ENCODING_END when EOF is seen. */
    Tcl_EolTranslation inputTranslation;
				/* What translation to apply for end of line
                                 * sequences on input? */    
    Tcl_EolTranslation outputTranslation;
    				/* What translation to use for generating
                                 * end of line sequences in output? */
    int inEofChar;		/* If nonzero, use this as a signal of EOF
                                 * on input. */
    int outEofChar;             /* If nonzero, append this to the channel
                                 * when it is closed if it is open for
                                 * writing. */
    int unreportedError;	/* Non-zero if an error report was deferred
                                 * because it happened in the background. The
                                 * value is the POSIX error code. */
    ClientData instanceData;	/* Instance-specific data provided by
				 * creator of channel. */

    Tcl_ChannelType *typePtr;	/* Pointer to channel type structure. */
    int refCount;		/* How many interpreters hold references to
                                 * this IO channel? */
    CloseCallback *closeCbPtr;	/* Callbacks registered to be called when the
                                 * channel is closed. */
    char *outputStage;		/* Temporary staging buffer used when
				 * translating EOL before converting from
				 * UTF-8 to external form. */
    ChannelBuffer *curOutPtr;	/* Current output buffer being filled. */
    ChannelBuffer *outQueueHead;/* Points at first buffer in output queue. */
    ChannelBuffer *outQueueTail;/* Points at last buffer in output queue. */

    ChannelBuffer *saveInBufPtr;/* Buffer saved for input queue - eliminates
                                 * need to allocate a new buffer for "gets"
                                 * that crosses buffer boundaries. */
    ChannelBuffer *inQueueHead;	/* Points at first buffer in input queue. */
    ChannelBuffer *inQueueTail;	/* Points at last buffer in input queue. */

    struct ChannelHandler *chPtr;/* List of channel handlers registered
                                  * for this channel. */
    int interestMask;		/* Mask of all events this channel has
                                 * handlers for. */
    struct Channel *nextChanPtr;/* Next in list of channels currently open. */
    EventScriptRecord *scriptRecordPtr;
    				/* Chain of all scripts registered for
                                 * event handlers ("fileevent") on this
                                 * channel. */
    int bufSize;		/* What size buffers to allocate? */
    Tcl_TimerToken timer;	/* Handle to wakeup timer for this channel. */
    CopyState *csPtr;		/* State of background copy, or NULL. */
    struct Channel* supercedes; /* Refers to channel this one was stacked upon.
				   This reference is NULL for normal channels.
				   See Tcl_StackChannel. */

} Channel;
    
/*
 * Values for the flags field in Channel. Any ORed combination of the
 * following flags can be stored in the field. These flags record various
 * options and state bits about the channel. In addition to the flags below,
 * the channel can also have TCL_READABLE (1<<1) and TCL_WRITABLE (1<<2) set.
 */

#define CHANNEL_NONBLOCKING	(1<<3)	/* Channel is currently in
					 * nonblocking mode. */
#define CHANNEL_LINEBUFFERED	(1<<4)	/* Output to the channel must be
					 * flushed after every newline. */
#define CHANNEL_UNBUFFERED	(1<<5)	/* Output to the channel must always
					 * be flushed immediately. */
#define BUFFER_READY		(1<<6)	/* Current output buffer (the
					 * curOutPtr field in the
                                         * channel structure) should be
                                         * output as soon as possible even
                                         * though it may not be full. */
#define BG_FLUSH_SCHEDULED	(1<<7)	/* A background flush of the
					 * queued output buffers has been
                                         * scheduled. */
#define CHANNEL_CLOSED		(1<<8)	/* Channel has been closed. No
					 * further Tcl-level IO on the
                                         * channel is allowed. */
#define CHANNEL_EOF		(1<<9)	/* EOF occurred on this channel.
					 * This bit is cleared before every
                                         * input operation. */
#define CHANNEL_STICKY_EOF	(1<<10)	/* EOF occurred on this channel because
					 * we saw the input eofChar. This bit
                                         * prevents clearing of the EOF bit
                                         * before every input operation. */
#define CHANNEL_BLOCKED	(1<<11)	/* EWOULDBLOCK or EAGAIN occurred
				 * on this channel. This bit is
				 * cleared before every input or
				 * output operation. */
#define INPUT_SAW_CR		(1<<12)	/* Channel is in CRLF eol input
					 * translation mode and the last
                                         * byte seen was a "\r". */
#define INPUT_NEED_NL		(1<<15)	/* Saw a '\r' at end of last buffer,
					 * and there should be a '\n' at
					 * beginning of next buffer. */
#define CHANNEL_DEAD		(1<<13)	/* The channel has been closed by
					 * the exit handler (on exit) but
                                         * not deallocated. When any IO
                                         * operation sees this flag on a
                                         * channel, it does not call driver
                                         * level functions to avoid referring
                                         * to deallocated data. */
#define CHANNEL_NEED_MORE_DATA	(1<<14)	/* The last input operation failed
					 * because there was not enough data
					 * to complete the operation.  This
					 * flag is set when gets fails to
					 * get a complete line or when read
					 * fails to get a complete character.
					 * When set, file events will not be
					 * delivered for buffered data until
					 * the state of the channel changes. */

/*
 * For each channel handler registered in a call to Tcl_CreateChannelHandler,
 * there is one record of the following type. All of records for a specific
 * channel are chained together in a singly linked list which is stored in
 * the channel structure.
 */

typedef struct ChannelHandler {
    Channel *chanPtr;		/* The channel structure for this channel. */
    int mask;			/* Mask of desired events. */
    Tcl_ChannelProc *proc;	/* Procedure to call in the type of
                                 * Tcl_CreateChannelHandler. */
    ClientData clientData;	/* Argument to pass to procedure. */
    struct ChannelHandler *nextPtr;
    				/* Next one in list of registered handlers. */
} ChannelHandler;

/*
 * This structure keeps track of the current ChannelHandler being invoked in
 * the current invocation of ChannelHandlerEventProc. There is a potential
 * problem if a ChannelHandler is deleted while it is the current one, since
 * ChannelHandlerEventProc needs to look at the nextPtr field. To handle this
 * problem, structures of the type below indicate the next handler to be
 * processed for any (recursively nested) dispatches in progress. The
 * nextHandlerPtr field is updated if the handler being pointed to is deleted.
 * The nextPtr field is used to chain together all recursive invocations, so
 * that Tcl_DeleteChannelHandler can find all the recursively nested
 * invocations of ChannelHandlerEventProc and compare the handler being
 * deleted against the NEXT handler to be invoked in that invocation; when it
 * finds such a situation, Tcl_DeleteChannelHandler updates the nextHandlerPtr
 * field of the structure to the next handler.
 */

typedef struct NextChannelHandler {
    ChannelHandler *nextHandlerPtr;	/* The next handler to be invoked in
                                         * this invocation. */
    struct NextChannelHandler *nestedHandlerPtr;
    /* Next nested invocation of
     * ChannelHandlerEventProc. */
} NextChannelHandler;


/*
 * The following structure describes the event that is added to the Tcl
 * event queue by the channel handler check procedure.
 */

typedef struct ChannelHandlerEvent {
    Tcl_Event header;		/* Standard header for all events. */
    Channel *chanPtr;		/* The channel that is ready. */
    int readyMask;		/* Events that have occurred. */
} ChannelHandlerEvent;

/*
 * The following structure is used by Tcl_GetsObj() to encapsulates the
 * state for a "gets" operation.
 */
 
typedef struct GetsState {
    Tcl_Obj *objPtr;		/* The object to which UTF-8 characters
				 * will be appended. */
    char **dstPtr;		/* Pointer into objPtr's string rep where
				 * next character should be stored. */
    Tcl_Encoding encoding;	/* The encoding to use to convert raw bytes
				 * to UTF-8.  */
    ChannelBuffer *bufPtr;	/* The current buffer of raw bytes being
				 * emptied. */
    Tcl_EncodingState state;	/* The encoding state just before the last
				 * external to UTF-8 conversion in
				 * FilterInputBytes(). */
    int rawRead;		/* The number of bytes removed from bufPtr
				 * in the last call to FilterInputBytes(). */
    int bytesWrote;		/* The number of bytes of UTF-8 data
				 * appended to objPtr during the last call to
				 * FilterInputBytes(). */
    int charsWrote;		/* The corresponding number of UTF-8
				 * characters appended to objPtr during the
				 * last call to FilterInputBytes(). */
    int totalChars;		/* The total number of UTF-8 characters
				 * appended to objPtr so far, just before the
				 * last call to FilterInputBytes(). */
} GetsState;

/*
 * All static variables used in this file are collected into a single
 * instance of the following structure.  For multi-threaded implementations,
 * there is one instance of this structure for each thread.
 *
 * Notice that different structures with the same name appear in other
 * files.  The structure defined below is used in this file only.
 */

typedef struct ThreadSpecificData {

    /*
     * This variable holds the list of nested ChannelHandlerEventProc 
     * invocations.
     */
    NextChannelHandler *nestedHandlerPtr;

    /*
     * List of all channels currently open.
     * List of all channels currently open, indexed by ChannelState,
     * as only one ChannelState exists per set of stacked channels.
     */
    Channel *firstChanPtr;
    ChannelState *firstCSPtr;
#ifdef oldcode
    /*
     * Has a channel exit handler been created yet?
     */
    int channelExitHandlerCreated;

    /*

/*
 * Static functions in this file:
 */

static ChannelBuffer *	AllocChannelBuffer _ANSI_ARGS_((int length));
static void		ChannelEventScriptInvoker _ANSI_ARGS_((
    ClientData clientData, int flags));
static void		ChannelTimerProc _ANSI_ARGS_((
    ClientData clientData));
static int		CheckChannelErrors _ANSI_ARGS_((Channel *chanPtr,
	int direction));
				ClientData clientData));
static int		CheckChannelErrors _ANSI_ARGS_((ChannelState *statePtr,
				int direction));
static int		CheckFlush _ANSI_ARGS_((Channel *chanPtr,
	ChannelBuffer *bufPtr, int newlineFlag));
				ChannelBuffer *bufPtr, int newlineFlag));
static int		CheckForDeadChannel _ANSI_ARGS_((Tcl_Interp *interp,
	Channel *chan));
				ChannelState *statePtr));
static void		CheckForStdChannelsBeingClosed _ANSI_ARGS_((
    Tcl_Channel chan));
				Tcl_Channel chan));
static void		CleanupChannelHandlers _ANSI_ARGS_((
    Tcl_Interp *interp, Channel *chanPtr));
				Tcl_Interp *interp, Channel *chanPtr));
static int		CloseChannel _ANSI_ARGS_((Tcl_Interp *interp,
	Channel *chanPtr, int errorCode));
				Channel *chanPtr, int errorCode));
static void		CommonGetsCleanup _ANSI_ARGS_((Channel *chanPtr,
	Tcl_Encoding encoding));
				Tcl_Encoding encoding));
static int		CopyAndTranslateBuffer _ANSI_ARGS_((
				ChannelState *statePtr, char *result,
				int space));
static int		CopyBuffer _ANSI_ARGS_((
    Channel *chanPtr, char *result, int space));
				Channel *chanPtr, char *result,
				int space));
static int		CopyData _ANSI_ARGS_((CopyState *csPtr, int mask));
static void		CopyEventProc _ANSI_ARGS_((ClientData clientData,
	int mask));
				int mask));
static void		CreateScriptRecord _ANSI_ARGS_((
    Tcl_Interp *interp, Channel *chanPtr,
    int mask, Tcl_Obj *scriptPtr));
				Tcl_Interp *interp, Channel *chanPtr,
				int mask, Tcl_Obj *scriptPtr));
static void		DeleteChannelTable _ANSI_ARGS_((
    ClientData clientData, Tcl_Interp *interp));
				ClientData clientData, Tcl_Interp *interp));
static void		DeleteScriptRecord _ANSI_ARGS_((Tcl_Interp *interp,
	Channel *chanPtr, int mask));
static void		DiscardInputQueued _ANSI_ARGS_((
    Channel *chanPtr, int discardSavedBuffers));
				Channel *chanPtr, int mask));
static void		DiscardInputQueued _ANSI_ARGS_((ChannelState *statePtr,
				int discardSavedBuffers));
static void		DiscardOutputQueued _ANSI_ARGS_((
    Channel *chanPtr));
				ChannelState *chanPtr));
static int		DoRead _ANSI_ARGS_((Channel *chanPtr, char *srcPtr,
	int slen));
				int slen));
static int		DoWrite _ANSI_ARGS_((Channel *chanPtr, char *src,
	int srcLen));
				int srcLen));
static int		FilterInputBytes _ANSI_ARGS_((Channel *chanPtr,
	GetsState *statePtr));
				GetsState *statePtr));
static int		FlushChannel _ANSI_ARGS_((Tcl_Interp *interp,
	Channel *chanPtr, int calledFromAsyncFlush));
				Channel *chanPtr, int calledFromAsyncFlush));
static Tcl_HashTable *	GetChannelTable _ANSI_ARGS_((Tcl_Interp *interp));
static int		GetInput _ANSI_ARGS_((Channel *chanPtr));
static void		PeekAhead _ANSI_ARGS_((Channel *chanPtr,
	char **dstEndPtr, GetsState *gsPtr));
static int		ReadBytes _ANSI_ARGS_((Channel *chanPtr,
	Tcl_Obj *objPtr, int charsLeft, int *offsetPtr));
static int		ReadChars _ANSI_ARGS_((Channel *chanPtr,
	Tcl_Obj *objPtr, int charsLeft, int *offsetPtr,
	int *factorPtr));
static void		RecycleBuffer _ANSI_ARGS_((Channel *chanPtr,
	ChannelBuffer *bufPtr, int mustDiscard));
				char **dstEndPtr, GetsState *gsPtr));
static int		ReadBytes _ANSI_ARGS_((ChannelState *statePtr,
				Tcl_Obj *objPtr, int charsLeft,
				int *offsetPtr));
static int		ReadChars _ANSI_ARGS_((ChannelState *statePtr,
				Tcl_Obj *objPtr, int charsLeft, int *offsetPtr,
				int *factorPtr));
static void		RecycleBuffer _ANSI_ARGS_((ChannelState *statePtr,
				ChannelBuffer *bufPtr, int mustDiscard));
static int		StackSetBlockMode _ANSI_ARGS_((Channel *chanPtr,
				int mode));
static int		SetBlockMode _ANSI_ARGS_((Tcl_Interp *interp,
	Channel *chanPtr, int mode));
				Channel *chanPtr, int mode));
static void		StopCopy _ANSI_ARGS_((CopyState *csPtr));
static int		TranslateInputEOL _ANSI_ARGS_((Channel *chanPtr,
	char *dst, CONST char *src, int *dstLenPtr,
	int *srcLenPtr));
static int		TranslateOutputEOL _ANSI_ARGS_((Channel *chanPtr,
	char *dst, CONST char *src, int *dstLenPtr,
	int *srcLenPtr));
static int		TranslateInputEOL _ANSI_ARGS_((ChannelState *statePtr,
				char *dst, CONST char *src, int *dstLenPtr,
				int *srcLenPtr));
static int		TranslateOutputEOL _ANSI_ARGS_((ChannelState *statePtr,
				char *dst, CONST char *src, int *dstLenPtr,
				int *srcLenPtr));
static void		UpdateInterest _ANSI_ARGS_((Channel *chanPtr));
static int		WriteBytes _ANSI_ARGS_((Channel *chanPtr,
	CONST char *src, int srcLen));
				CONST char *src, int srcLen));
static int		WriteChars _ANSI_ARGS_((Channel *chanPtr,
	CONST char *src, int srcLen));
				CONST char *src, int srcLen));


/*
 *---------------------------------------------------------------------------
 *
 * TclInitIOSubsystem --
 *

	/* ARGSUSED */
void
TclFinalizeIOSubsystem()
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    Channel *chanPtr;			/* Iterates over open channels. */
    Channel *nextChanPtr;		/* Iterates over open channels. */

    ChannelState *nextCSPtr;		/* Iterates over open channels. */
    ChannelState *statePtr;		/* state of channel stack */

    for (chanPtr = tsdPtr->firstChanPtr; chanPtr != (Channel *) NULL;
	 chanPtr = nextChanPtr) {
        nextChanPtr = chanPtr->nextChanPtr;
    for (statePtr = tsdPtr->firstCSPtr; statePtr != (ChannelState *) NULL;
	 statePtr = nextCSPtr) {
	chanPtr		= statePtr->topChanPtr;
        nextCSPtr	= statePtr->nextCSPtr;

        /*
         * Set the channel back into blocking mode to ensure that we wait
         * for all data to flush out.
         */
        
        (void) Tcl_SetChannelOption(NULL, (Tcl_Channel) chanPtr,
                "-blocking", "on");

        if ((chanPtr == (Channel *) tsdPtr->stdinChannel) ||
                (chanPtr == (Channel *) tsdPtr->stdoutChannel) ||
                (chanPtr == (Channel *) tsdPtr->stderrChannel)) {

            /*
             * Decrement the refcount which was earlier artificially bumped
             * up to keep the channel from being closed.
             */

            chanPtr->refCount--;
            statePtr->refCount--;
        }

        if (chanPtr->refCount <= 0) {
        if (statePtr->refCount <= 0) {

	    /*
             * Close it only if the refcount indicates that the channel is not
             * referenced from any interpreter. If it is, that interpreter will
             * close the channel when it gets destroyed.
             */

             * Finally, we clean up the fields in the channel data structure
             * since all of them have been deleted already. We mark the
             * channel with CHANNEL_DEAD to prevent any further IO operations
             * on it.
             */

            chanPtr->instanceData = (ClientData) NULL;
            chanPtr->flags |= CHANNEL_DEAD;
            statePtr->flags |= CHANNEL_DEAD;
        }
    }
}


/*
 *----------------------------------------------------------------------

    Tcl_Channel chan;		/* The channel for which to create the
                                 * close callback. */
    Tcl_CloseProc *proc;	/* The callback routine to call when the
                                 * channel will be closed. */
    ClientData clientData;	/* Arbitrary data to pass to the
                                 * close callback. */
{
    Channel *chanPtr;
    ChannelState *statePtr;
    CloseCallback *cbPtr;

    chanPtr = (Channel *) chan;
    statePtr = ((Channel *) chan)->state;

    cbPtr = (CloseCallback *) ckalloc((unsigned) sizeof(CloseCallback));
    cbPtr->proc = proc;
    cbPtr->clientData = clientData;

    cbPtr->nextPtr = chanPtr->closeCbPtr;
    chanPtr->closeCbPtr = cbPtr;
    cbPtr->nextPtr = statePtr->closeCbPtr;
    statePtr->closeCbPtr = cbPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DeleteCloseHandler --
 *

    Tcl_Channel chan;		/* The channel for which to cancel the
                                 * close callback. */
    Tcl_CloseProc *proc;	/* The procedure for the callback to
                                 * remove. */
    ClientData clientData;	/* The callback data for the callback
                                 * to remove. */
{
    Channel *chanPtr;
    ChannelState *statePtr;
    CloseCallback *cbPtr, *cbPrevPtr;

    chanPtr = (Channel *) chan;
    for (cbPtr = chanPtr->closeCbPtr, cbPrevPtr = (CloseCallback *) NULL;
    statePtr = ((Channel *) chan)->state;
    for (cbPtr = statePtr->closeCbPtr, cbPrevPtr = (CloseCallback *) NULL;
	 cbPtr != (CloseCallback *) NULL;
	 cbPtr = cbPtr->nextPtr) {
        if ((cbPtr->proc == proc) && (cbPtr->clientData == clientData)) {
            if (cbPrevPtr == (CloseCallback *) NULL) {
                chanPtr->closeCbPtr = cbPtr->nextPtr;
                statePtr->closeCbPtr = cbPtr->nextPtr;
            }
            ckfree((char *) cbPtr);
            break;
        } else {
            cbPrevPtr = cbPtr;
        }
    }

DeleteChannelTable(clientData, interp)
    ClientData clientData;	/* The per-interpreter data structure. */
    Tcl_Interp *interp;		/* The interpreter being deleted. */
{
    Tcl_HashTable *hTblPtr;	/* The hash table. */
    Tcl_HashSearch hSearch;	/* Search variable. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    Channel *chanPtr;	/* Channel being deleted. */
    Channel *chanPtr;		/* Channel being deleted. */
    ChannelState *statePtr;	/* State of Channel being deleted. */
    EventScriptRecord *sPtr, *prevPtr, *nextPtr;
    				/* Variables to loop over all channel events
                                 * registered, to delete the ones that refer
                                 * to the interpreter being deleted. */
    

    /*
     * Delete all the registered channels - this will close channels whose
     * refcount reaches zero.
     */
    
    hTblPtr = (Tcl_HashTable *) clientData;
    for (hPtr = Tcl_FirstHashEntry(hTblPtr, &hSearch);
	 hPtr != (Tcl_HashEntry *) NULL;
	 hPtr = Tcl_FirstHashEntry(hTblPtr, &hSearch)) {

        chanPtr = (Channel *) Tcl_GetHashValue(hPtr);
	statePtr = chanPtr->state;

        /*
         * Remove any fileevents registered in this interpreter.
         */
        
        for (sPtr = chanPtr->scriptRecordPtr,
        for (sPtr = statePtr->scriptRecordPtr,
                 prevPtr = (EventScriptRecord *) NULL;
	     sPtr != (EventScriptRecord *) NULL;
	     sPtr = nextPtr) {
            nextPtr = sPtr->nextPtr;
            if (sPtr->interp == interp) {
                if (prevPtr == (EventScriptRecord *) NULL) {
                    chanPtr->scriptRecordPtr = nextPtr;
                    statePtr->scriptRecordPtr = nextPtr;
                } else {
                    prevPtr->nextPtr = nextPtr;
                }

                Tcl_DeleteChannelHandler((Tcl_Channel) chanPtr,
                        ChannelEventScriptInvoker, (ClientData) sPtr);
                        TclChannelEventScriptInvoker, (ClientData) sPtr);

		Tcl_DecrRefCount(sPtr->scriptPtr);
                ckfree((char *) sPtr);
            } else {
                prevPtr = sPtr;
            }
        }

        /*
         * Cannot call Tcl_UnregisterChannel because that procedure calls
         * Tcl_GetAssocData to get the channel table, which might already
         * be inaccessible from the interpreter structure. Instead, we
         * emulate the behavior of Tcl_UnregisterChannel directly here.
         */

        Tcl_DeleteHashEntry(hPtr);
        chanPtr->refCount--;
        if (chanPtr->refCount <= 0) {
            if (!(chanPtr->flags & BG_FLUSH_SCHEDULED)) {
        statePtr->refCount--;
        if (statePtr->refCount <= 0) {
            if (!(statePtr->flags & BG_FLUSH_SCHEDULED)) {
                (void) Tcl_Close(interp, (Tcl_Channel) chanPtr);
            }
        }
    }
    Tcl_DeleteHashTable(hTblPtr);
    ckfree((char *) hTblPtr);
}

 *----------------------------------------------------------------------
 */

static void
CheckForStdChannelsBeingClosed(chan)
    Tcl_Channel chan;
{
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = ((Channel *) chan)->state;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if ((chan == tsdPtr->stdinChannel) && (tsdPtr->stdinInitialized)) {
        if (chanPtr->refCount < 2) {
            chanPtr->refCount = 0;
        if (statePtr->refCount < 2) {
            statePtr->refCount = 0;
            tsdPtr->stdinChannel = NULL;
            return;
        }
    } else if ((chan == tsdPtr->stdoutChannel) && (tsdPtr->stdoutInitialized)) {
        if (chanPtr->refCount < 2) {
            chanPtr->refCount = 0;
    } else if ((chan == tsdPtr->stdoutChannel)
	    && (tsdPtr->stdoutInitialized)) {
        if (statePtr->refCount < 2) {
            statePtr->refCount = 0;
            tsdPtr->stdoutChannel = NULL;
            return;
        }
    } else if ((chan == tsdPtr->stderrChannel) && (tsdPtr->stderrInitialized)) {
        if (chanPtr->refCount < 2) {
            chanPtr->refCount = 0;
    } else if ((chan == tsdPtr->stderrChannel)
	    && (tsdPtr->stderrInitialized)) {
        if (statePtr->refCount < 2) {
            statePtr->refCount = 0;
            tsdPtr->stderrChannel = NULL;
            return;
        }
    }
}

/*

    Tcl_Channel chan;		/* The channel to add to this interpreter
                                 * channel table. */
{
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    int new;			/* Is the hash entry new or does it exist? */
    Channel *chanPtr;		/* The actual channel. */
    ChannelState *statePtr;	/* State of the actual channel. */

    /*
     * Always (un)register bottom-most channel in the stack.  This makes
     * management of the channel list easier because no manipulation is
     * necessary during (un)stack operation.
     */
    chanPtr = (Channel *) chan;
    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    statePtr = chanPtr->state;

    if (chanPtr->channelName == (char *) NULL) {
    if (statePtr->channelName == (char *) NULL) {
        panic("Tcl_RegisterChannel: channel without name");
    }
    if (interp != (Tcl_Interp *) NULL) {
        hTblPtr = GetChannelTable(interp);
        hPtr = Tcl_CreateHashEntry(hTblPtr, chanPtr->channelName, &new);
        hPtr = Tcl_CreateHashEntry(hTblPtr, statePtr->channelName, &new);
        if (new == 0) {
            if (chan == (Tcl_Channel) Tcl_GetHashValue(hPtr)) {
                return;
            }

	    /* Andreas Kupries <a.kupries@westend.com>, 12/13/1998
	     * "Trf-Patch for filtering channels"
	     *
	     * This is the change to 'Tcl_RegisterChannel'.
	     *
	     * Explanation:
	     *		The moment a channel is stacked upon another he
	     *		takes the identity of the channel he supercedes,
	     *		i.e. he gets the *same* name. Because of this we
	     *		cannot check for duplicate names anymore, they
	     *		have to be allowed now.
	     */

	    /* panic("Tcl_RegisterChannel: duplicate channel names"); */
	    panic("Tcl_RegisterChannel: duplicate channel names");
        }
        Tcl_SetHashValue(hPtr, (ClientData) chanPtr);
    }
    chanPtr->refCount++;
    statePtr->refCount++;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnregisterChannel --
 *

Tcl_UnregisterChannel(interp, chan)
    Tcl_Interp *interp;		/* Interpreter in which channel is defined. */
    Tcl_Channel chan;		/* Channel to delete. */
{
    Tcl_HashTable *hTblPtr;	/* Hash table of channels. */
    Tcl_HashEntry *hPtr;	/* Search variable. */
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of the real channel. */

    /*
     * Always (un)register bottom-most channel in the stack.  This makes
     * management of the channel list easier because no manipulation is
     * necessary during (un)stack operation.
     */
    chanPtr = (Channel *) chan;
    
    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    statePtr = chanPtr->state;

    if (interp != (Tcl_Interp *) NULL) {
        hTblPtr = (Tcl_HashTable *) Tcl_GetAssocData(interp, "tclIO", NULL);
        if (hTblPtr == (Tcl_HashTable *) NULL) {
            return TCL_OK;
        }
        hPtr = Tcl_FindHashEntry(hTblPtr, chanPtr->channelName);
        hPtr = Tcl_FindHashEntry(hTblPtr, statePtr->channelName);
        if (hPtr == (Tcl_HashEntry *) NULL) {
            return TCL_OK;
        }
        if ((Channel *) Tcl_GetHashValue(hPtr) != chanPtr) {
            return TCL_OK;
        }
        Tcl_DeleteHashEntry(hPtr);

        /*
         * Remove channel handlers that refer to this interpreter, so that they
         * will not be present if the actual close is delayed and more events
         * happen on the channel. This may occur if the channel is shared
         * between several interpreters, or if the channel has async
         * flushing active.
         */
    
        CleanupChannelHandlers(interp, chanPtr);
    }

    chanPtr->refCount--;
    statePtr->refCount--;
    
    /*
     * Perform special handling for standard channels being closed. If the
     * refCount is now 1 it means that the last reference to the standard
     * channel is being explicitly closed, so bump the refCount down
     * artificially to 0. This will ensure that the channel is actually
     * closed, below. Also set the static pointer to NULL for the channel.
     */

    CheckForStdChannelsBeingClosed(chan);

    /*
     * If the refCount reached zero, close the actual channel.
     */

    if (chanPtr->refCount <= 0) {
    if (statePtr->refCount <= 0) {

        /*
         * Ensure that if there is another buffer, it gets flushed
         * whether or not we are doing a background flush.
         */

        if ((chanPtr->curOutPtr != NULL) &&
                (chanPtr->curOutPtr->nextAdded >
                        chanPtr->curOutPtr->nextRemoved)) {
            chanPtr->flags |= BUFFER_READY;
        if ((statePtr->curOutPtr != NULL) &&
                (statePtr->curOutPtr->nextAdded >
                        statePtr->curOutPtr->nextRemoved)) {
            statePtr->flags |= BUFFER_READY;
        }
        chanPtr->flags |= CHANNEL_CLOSED;
        if (!(chanPtr->flags & BG_FLUSH_SCHEDULED)) {
        statePtr->flags |= CHANNEL_CLOSED;
        if (!(statePtr->flags & BG_FLUSH_SCHEDULED)) {
            if (Tcl_Close(interp, chan) != TCL_OK) {
                return TCL_ERROR;
            }
        }
    }
    return TCL_OK;
}

     * have access to the standard channels.
     */

    name = chanName;
    if ((chanName[0] == 's') && (chanName[1] == 't')) {
	chanPtr = NULL;
	if (strcmp(chanName, "stdin") == 0) {
	    chanPtr = (Channel *)Tcl_GetStdChannel(TCL_STDIN);
	    chanPtr = (Channel *) Tcl_GetStdChannel(TCL_STDIN);
	} else if (strcmp(chanName, "stdout") == 0) {
	    chanPtr = (Channel *)Tcl_GetStdChannel(TCL_STDOUT);
	    chanPtr = (Channel *) Tcl_GetStdChannel(TCL_STDOUT);
	} else if (strcmp(chanName, "stderr") == 0) {
	    chanPtr = (Channel *)Tcl_GetStdChannel(TCL_STDERR);
	    chanPtr = (Channel *) Tcl_GetStdChannel(TCL_STDERR);
	}
	if (chanPtr != NULL) {
	    name = chanPtr->channelName;
	    name = chanPtr->state->channelName;
	}
    }
    

    hTblPtr = GetChannelTable(interp);
    hPtr = Tcl_FindHashEntry(hTblPtr, name);
    if (hPtr == (Tcl_HashEntry *) NULL) {
        Tcl_AppendResult(interp, "can not find channel named \"",
                chanName, "\"", (char *) NULL);
        return NULL;
    }

    /*
     * Always return bottom-most channel in the stack.  This one lives
     * the longest - other channels may go away unnoticed.
     * The other APIs compensate where necessary to retrieve the
     * topmost channel again.
     */
    chanPtr = (Channel *) Tcl_GetHashValue(hPtr);
    chanPtr = chanPtr->state->bottomChanPtr;
    if (modePtr != NULL) {
        *modePtr = (chanPtr->flags & (TCL_READABLE|TCL_WRITABLE));
        *modePtr = (chanPtr->state->flags & (TCL_READABLE|TCL_WRITABLE));
    }
    
    return (Tcl_Channel) chanPtr;
}

/*
 *----------------------------------------------------------------------

    Tcl_ChannelType *typePtr;	/* The channel type record. */
    char *chanName;		/* Name of channel to record. */
    ClientData instanceData;	/* Instance specific data. */
    int mask;			/* TCL_READABLE & TCL_WRITABLE to indicate
                                 * if the channel is readable, writable. */
{
    Channel *chanPtr;		/* The channel structure newly created. */
    ChannelState *statePtr;	/* The stack-level independent state info
				 * for the channel. */
    CONST char *name;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    chanPtr = (Channel *) ckalloc((unsigned) sizeof(Channel));
    
    chanPtr  = (Channel *) ckalloc((unsigned) sizeof(Channel));
    statePtr = (ChannelState *) ckalloc((unsigned) sizeof(ChannelState));
    chanPtr->state = statePtr;

    chanPtr->instanceData	= instanceData;
    chanPtr->typePtr		= typePtr;

    /*
     * Set all the bits that are part of the stack-independent state
     * information for the channel.
     */

    if (chanName != (char *) NULL) {
        chanPtr->channelName = ckalloc((unsigned) (strlen(chanName) + 1));
        strcpy(chanPtr->channelName, chanName);
        statePtr->channelName = ckalloc((unsigned) (strlen(chanName) + 1));
        strcpy(statePtr->channelName, chanName);
    } else {
        panic("Tcl_CreateChannel: NULL channel name");
    }

    chanPtr->flags = mask;
    statePtr->flags		= mask;

    /*
     * Set the channel to system default encoding.
     */

    chanPtr->encoding = NULL;
    statePtr->encoding = NULL;
    name = Tcl_GetEncodingName(NULL);
    if (strcmp(name, "binary") != 0) {
    	chanPtr->encoding = Tcl_GetEncoding(NULL, name);
    	statePtr->encoding = Tcl_GetEncoding(NULL, name);
    }
    chanPtr->inputEncodingState = NULL;
    chanPtr->inputEncodingFlags = TCL_ENCODING_START;
    chanPtr->outputEncodingState = NULL;
    chanPtr->outputEncodingFlags = TCL_ENCODING_START;
    statePtr->inputEncodingState	= NULL;
    statePtr->inputEncodingFlags	= TCL_ENCODING_START;
    statePtr->outputEncodingState	= NULL;
    statePtr->outputEncodingFlags	= TCL_ENCODING_START;

    /*
     * Set the channel up initially in AUTO input translation mode to
     * accept "\n", "\r" and "\r\n". Output translation mode is set to
     * a platform specific default value. The eofChar is set to 0 for both
     * input and output, so that Tcl does not look for an in-file EOF
     * indicator (e.g. ^Z) and does not append an EOF indicator to files.
     */

    chanPtr->inputTranslation = TCL_TRANSLATE_AUTO;
    chanPtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
    chanPtr->inEofChar = 0;
    chanPtr->outEofChar = 0;
    statePtr->inputTranslation	= TCL_TRANSLATE_AUTO;
    statePtr->outputTranslation	= TCL_PLATFORM_TRANSLATION;
    statePtr->inEofChar		= 0;
    statePtr->outEofChar	= 0;

    chanPtr->unreportedError = 0;
    statePtr->unreportedError	= 0;
    chanPtr->instanceData = instanceData;
    chanPtr->typePtr = typePtr;
    chanPtr->refCount = 0;
    chanPtr->closeCbPtr = (CloseCallback *) NULL;
    chanPtr->curOutPtr = (ChannelBuffer *) NULL;
    chanPtr->outQueueHead = (ChannelBuffer *) NULL;
    chanPtr->outQueueTail = (ChannelBuffer *) NULL;
    chanPtr->saveInBufPtr = (ChannelBuffer *) NULL;
    chanPtr->inQueueHead = (ChannelBuffer *) NULL;
    chanPtr->inQueueTail = (ChannelBuffer *) NULL;
    chanPtr->chPtr = (ChannelHandler *) NULL;
    chanPtr->interestMask = 0;
    chanPtr->scriptRecordPtr = (EventScriptRecord *) NULL;
    chanPtr->bufSize = CHANNELBUFFER_DEFAULT_SIZE;
    chanPtr->timer = NULL;
    chanPtr->csPtr = NULL;
    statePtr->refCount		= 0;
    statePtr->closeCbPtr	= (CloseCallback *) NULL;
    statePtr->curOutPtr		= (ChannelBuffer *) NULL;
    statePtr->outQueueHead	= (ChannelBuffer *) NULL;
    statePtr->outQueueTail	= (ChannelBuffer *) NULL;
    statePtr->saveInBufPtr	= (ChannelBuffer *) NULL;
    statePtr->inQueueHead	= (ChannelBuffer *) NULL;
    statePtr->inQueueTail	= (ChannelBuffer *) NULL;
    statePtr->chPtr		= (ChannelHandler *) NULL;
    statePtr->interestMask	= 0;
    statePtr->scriptRecordPtr	= (EventScriptRecord *) NULL;
    statePtr->bufSize		= CHANNELBUFFER_DEFAULT_SIZE;
    statePtr->timer		= NULL;
    statePtr->csPtr		= NULL;
    chanPtr->supercedes = (Channel*) NULL;

    chanPtr->outputStage = NULL;
    if ((chanPtr->encoding != NULL) && (chanPtr->flags & TCL_WRITABLE)) {
	chanPtr->outputStage = (char *)
	    ckalloc((unsigned) (chanPtr->bufSize + 2));
    statePtr->outputStage	= NULL;
    if ((statePtr->encoding != NULL) && (statePtr->flags & TCL_WRITABLE)) {
	statePtr->outputStage = (char *)
	    ckalloc((unsigned) (statePtr->bufSize + 2));
    }

    /*
     * As we are creating the channel, it is obviously the top for now
     */
    statePtr->topChanPtr	= chanPtr;
    statePtr->bottomChanPtr	= chanPtr;
    chanPtr->downChanPtr	= (Channel *) NULL;
    chanPtr->upChanPtr		= (Channel *) NULL;
    chanPtr->inQueueHead        = (ChannelBuffer*) NULL;
    chanPtr->inQueueTail        = (ChannelBuffer*) NULL;

    /*
     * Link the channel into the list of all channels; create an on-exit
     * handler if there is not one already, to close off all the channels
     * in the list on exit.
     */

    chanPtr->nextChanPtr = tsdPtr->firstChanPtr;
    tsdPtr->firstChanPtr = chanPtr;
    statePtr->nextCSPtr  = tsdPtr->firstCSPtr;
    tsdPtr->firstCSPtr   = statePtr;

    /*
     * Install this channel in the first empty standard channel slot, if
     * the channel was previously closed explicitly.
     */

    if ((tsdPtr->stdinChannel == NULL) && (tsdPtr->stdinInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel)chanPtr, TCL_STDIN);
    if ((tsdPtr->stdinChannel == NULL) &&
	    (tsdPtr->stdinInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDIN);
        Tcl_RegisterChannel((Tcl_Interp *) NULL, (Tcl_Channel) chanPtr);
    } else if ((tsdPtr->stdoutChannel == NULL) && (tsdPtr->stdoutInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel)chanPtr, TCL_STDOUT);
    } else if ((tsdPtr->stdoutChannel == NULL) &&
	    (tsdPtr->stdoutInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDOUT);
        Tcl_RegisterChannel((Tcl_Interp *) NULL, (Tcl_Channel) chanPtr);
    } else if ((tsdPtr->stderrChannel == NULL) && (tsdPtr->stderrInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel)chanPtr, TCL_STDERR);
    } else if ((tsdPtr->stderrChannel == NULL) &&
	    (tsdPtr->stderrInitialized == 1)) {
	Tcl_SetStdChannel((Tcl_Channel) chanPtr, TCL_STDERR);
        Tcl_RegisterChannel((Tcl_Interp *) NULL, (Tcl_Channel) chanPtr);
    } 
    return (Tcl_Channel) chanPtr;
}

/*
 *----------------------------------------------------------------------

 *    replaced by the new typePtr.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_StackChannel(interp, typePtr, instanceData, mask, prevChan)
    Tcl_Interp*      interp;       /* The interpreter we are working in */
    Tcl_Interp	    *interp;	   /* The interpreter we are working in */
    Tcl_ChannelType *typePtr;	   /* The channel type record for the new
				    * channel. */
    ClientData       instanceData; /* Instance specific data for the new
    ClientData	     instanceData; /* Instance specific data for the new
				    * channel. */
    int              mask;	   /* TCL_READABLE & TCL_WRITABLE to indicate
    int		     mask;	   /* TCL_READABLE & TCL_WRITABLE to indicate
				    * if the channel is readable, writable. */
    Tcl_Channel      prevChan;	   /* The channel structure to replace */
    Tcl_Channel	     prevChan;	   /* The channel structure to replace */
{
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    Channel            *chanPtr, *pt;
    int                 interest = 0;
    ThreadSpecificData	*tsdPtr = TCL_TSD_INIT(&dataKey);
    Channel		*chanPtr, *prevChanPtr;
    ChannelState	*statePtr;

    /*
     * AK, 06/30/1999
     *
     * Tcl_StackChannel differs from Tcl_ReplaceChannel of the
     * original "Trf" patch. Instead of seeing the
     * newly created structure as the *new* channel to cover the specified
     * one use it to *save* the current state of the specified channel and
     * then reinitialize the current structure for the given transformation.
     * Find the given channel in the list of all channels.
     * If we don't find it, then it was never registered correctly.
     *
     * Advantages:
     * - No splicing into the (thread-)global list of channels (or the per-
     *   interp hash-tables).
     * - Users of the C-API still have valid channel references even after
     *   the call to this procedure.
     *
     * Disadvantages:
     * - Untested code.
     */

     * This operation should occur at the top of a channel stack.
    /*
     * Find the given channel in the list of all channels.
     */

    pt     = (Channel*) tsdPtr->firstChanPtr;
    statePtr    = (ChannelState *) tsdPtr->firstCSPtr;
    prevChanPtr = ((Channel *) prevChan)->state->topChanPtr;

    while (pt != (Channel *) prevChan) {
	pt = pt->nextChanPtr;
    while (statePtr->topChanPtr != prevChanPtr) {
	statePtr = statePtr->nextCSPtr;
    }

    /*
     * 'pt == prevChan' now (or NULL, if not found).
    if (statePtr == NULL) {
     */

	Tcl_AppendResult(interp, "couldn't find state for channel \"",
    if (!pt) {
		Tcl_GetChannelName(prevChan), "\"", (char *) NULL);
        return (Tcl_Channel) NULL;
    }

    /*
     * Here we check if the given "mask" matches the "flags"
     * of the already existing channel.
     *
     *	  | - | R | W | RW |
     *	--+---+---+---+----+	<=>  0 != (chan->mask & prevChan->mask)
     *	- |   |   |   |    |
     *	R |   | + |   | +  |	The superceding channel is allowed to
     *	W |   |   | + | +  |	restrict the capabilities of the
     *	RW|   | + | + | +  |	superceded one !
     *	--+---+---+---+----+
     */

    if ((mask & (statePtr->flags & (TCL_READABLE | TCL_WRITABLE))) == 0) {
	Tcl_AppendResult(interp,
		"reading and writing both disallowed for channel \"",
    if ((mask & Tcl_GetChannelMode (prevChan)) == 0) {
		Tcl_GetChannelName(prevChan), "\"", (char *) NULL);
        return (Tcl_Channel) NULL;
    }

    /*
     * Flush the buffers. This ensures that any data still in them
     * at this time is not handled by the new transformation. Restrict
     * this to writable channels. Take care to hide a possible bg-copy
     * in progress from Tcl_Flush and the CheckForChannelErrors inside.
     */
    chanPtr = (Channel *) ckalloc((unsigned) sizeof(Channel));

    if ((mask & TCL_WRITABLE) != 0) {
        CopyState *csPtr;

        csPtr           = statePtr->csPtr;
	statePtr->csPtr = (CopyState*) NULL;

	if (Tcl_Flush((Tcl_Channel) prevChanPtr) != TCL_OK) {
	    statePtr->csPtr = csPtr;
	    Tcl_AppendResult(interp, "could not flush channel \"",
		    Tcl_GetChannelName(prevChan), "\"", (char *) NULL);
	    return (Tcl_Channel) NULL;
	}

	statePtr->csPtr = csPtr;
    }
    /*
     * Discard any input in the buffers. They are not yet read by the
     * If there is some interest in the channel, remove it, break
     * down the whole chain. It will be reconstructed later.
     * user of the channel, so they have to go through the new
     * transformation before reading. As the buffers contain the
     * untransformed form their contents are not only useless but actually
     * distorts our view of the system.
     *
     * To preserve the information without having to read them again and
     * to avoid problems with the location in the channel (seeking might
     * be impossible) we move the buffers from the common state structure
     * into the channel itself. We use the buffers in the channel below
     * the new transformation to hold the data. In the future this allows
     * us to write transformations which pre-read data and push the unused
     * part back when they are going away.
     */

    if (((mask & TCL_READABLE) != 0) &&
	(statePtr->inQueueHead != (ChannelBuffer*) NULL)) {
      /*
       * Remark: It is possible that the channel buffers contain data from
       * some earlier push-backs.
       */
    interest = pt->interestMask;

      statePtr->inQueueTail->nextPtr = prevChanPtr->inQueueHead;
      prevChanPtr->inQueueHead       = statePtr->inQueueHead;

      if (prevChanPtr->inQueueTail == (ChannelBuffer*) NULL) {
    pt->interestMask = 0;

    if (interest) {
        (pt->typePtr->watchProc) (pt->instanceData, 0);
	prevChanPtr->inQueueTail = statePtr->inQueueTail;
      }

      statePtr->inQueueHead          = (ChannelBuffer*) NULL;
      statePtr->inQueueTail          = (ChannelBuffer*) NULL;
    }

    chanPtr = (Channel *) ckalloc((unsigned) sizeof(Channel));

    /*
     * Save some of the current state into the new structure,
     * reinitialize the parts which will stay with the transformation.
     *
     * Remarks:
     * - We cannot discard the buffers, and they cannot be used from the
     *   transformation placed later into the 'pt' structure. Save them,
     *   and believe that Tcl_SetChannelOption (buffering, none) will do
     *   the right thing.
     * - encoding and EOL-translation control information is initialized
     *   to values for 'binary'. This is later reinforced via
     *   Tcl_SetChanneloption to get the handling of flags and the event
     *   system right.
     * - The 'interestMask' of the saved channel is cleared, but the
     *   transformations WatchProc is used to establish the connection
     *   between transformation and underlying channel. This should
     *   reestablish the correct mask.
     * - TTO = Transform Takes Over.   The hidden channel no longer
     *         needs to perform this function.
     */

    chanPtr->channelName = (char *) ckalloc (strlen(pt->channelName)+1);
    strcpy (chanPtr->channelName, pt->channelName);

    chanPtr->state		= statePtr;
    chanPtr->flags               = pt->flags;           /* Save */

    chanPtr->encoding            = (Tcl_Encoding) NULL; /* == 'binary' */
    chanPtr->inputEncodingState  = (Tcl_EncodingState) NULL;
    chanPtr->inputEncodingFlags  = TCL_ENCODING_START;
    chanPtr->outputEncodingState = (Tcl_EncodingState) NULL;
    chanPtr->outputEncodingFlags = TCL_ENCODING_START;

    chanPtr->inputTranslation    = TCL_TRANSLATE_LF; /* == 'binary' */
    chanPtr->outputTranslation   = TCL_TRANSLATE_LF; /* == 'binary' */
    chanPtr->inEofChar           = pt->inEofChar;         /* Save */
    chanPtr->outEofChar          = pt->outEofChar;        /* Save */

    chanPtr->unreportedError     = pt->unreportedError;   /* Save */
    chanPtr->instanceData        = pt->instanceData;      /* Save */
    chanPtr->typePtr             = pt->typePtr;           /* Save */
    chanPtr->instanceData	= instanceData;
    chanPtr->typePtr		= typePtr;
    chanPtr->refCount            = 0;   /* None, as the structure is covered */
    chanPtr->closeCbPtr          = (CloseCallback*) NULL; /* TTO */

    chanPtr->outputStage         = (char*) NULL;
    chanPtr->downChanPtr	= prevChanPtr;
    chanPtr->upChanPtr		= (Channel *) NULL;
    chanPtr->curOutPtr           = pt->curOutPtr;    /* Save */
    chanPtr->outQueueHead        = pt->outQueueHead; /* Save */
    chanPtr->outQueueTail        = pt->outQueueTail; /* Save */
    chanPtr->saveInBufPtr        = pt->saveInBufPtr; /* Save */
    chanPtr->inQueueHead         = pt->inQueueHead;  /* Save */
    chanPtr->inQueueTail         = pt->inQueueTail;  /* Save */
    chanPtr->inQueueHead        = (ChannelBuffer*) NULL;
    chanPtr->inQueueTail        = (ChannelBuffer*) NULL;

    chanPtr->chPtr               = (ChannelHandler *) NULL;  /* TTO */
    chanPtr->interestMask        = 0;
    chanPtr->nextChanPtr         = (Channel*) NULL;     /* Is not in list! */
    chanPtr->scriptRecordPtr     = (EventScriptRecord *) NULL; /* TTO */
    chanPtr->bufSize             = CHANNELBUFFER_DEFAULT_SIZE;
    chanPtr->timer               = (Tcl_TimerToken) NULL;      /* TTO */
    chanPtr->csPtr               = (CopyState*) NULL;          /* TTO */

    /*
     * Place new block at the head of a possibly existing list of previously
     * stacked channels, then do the missing initializations of translation
     * stacked channels.
     * and buffer system.
     */

    chanPtr->supercedes          = pt->supercedes;

    prevChanPtr->upChanPtr	= chanPtr;
    Tcl_SetChannelOption (interp, (Tcl_Channel) chanPtr,
	    "-translation", "binary");
    Tcl_SetChannelOption (interp, (Tcl_Channel) chanPtr,
	    "-buffering",   "none");

    statePtr->topChanPtr	= chanPtr;
    /*
     * Save accomplished, now reinitialize the (old) structure for the
     * transformation.
     *
     * - The information about encoding and eol-translation is taken
     *   without change.  There is no need to fiddle with
     *   refCount et. al.
     *
     * Don't forget to use the same blocking mode as the old channel.
     */

    pt->flags               = mask | (chanPtr->flags & CHANNEL_NONBLOCKING);

    /*
     * EDITORS NOTE:  all the lines with "take it as is" should get
     * deleted once this code has been debugged.
     */

    /* pt->encoding,            take it as is */
    /* pt->inputEncodingState,  take it as is */
    /* pt->inputEncodingFlags,  take it as is */
    /* pt->outputEncodingState, take it as is */
    /* pt->outputEncodingFlags, take it as is */

    /* pt->inputTranslation,    take it as is */
    /* pt->outputTranslation,   take it as is */

    /*
     * No special EOF character, that condition is determined by the
     * old channel
     */

    pt->inEofChar           = 0;
    pt->outEofChar          = 0;

    pt->unreportedError     = 0; /* No errors yet */
    pt->instanceData        = instanceData; /* Transformation state */
    pt->typePtr             = typePtr;      /* Transformation type */
    /* pt->refCount,            take it as it is */
    /* pt->closeCbPtr,          take it as it is */

    /* pt->outputStage,         take it as it is */
    pt->curOutPtr           = (ChannelBuffer *) NULL;
    pt->outQueueHead        = (ChannelBuffer *) NULL;
    pt->outQueueTail        = (ChannelBuffer *) NULL;
    pt->saveInBufPtr        = (ChannelBuffer *) NULL;
    pt->inQueueHead         = (ChannelBuffer *) NULL;
    pt->inQueueTail         = (ChannelBuffer *) NULL;

    /* pt->chPtr,               take it as it is */
    /* pt->interestMask,        take it as it is */
    /* pt->nextChanPtr,         take it as it is */
    /* pt->scriptRecordPtr,     take it as it is */
    pt->bufSize             = CHANNELBUFFER_DEFAULT_SIZE;
    /* pt->timer,               take it as it is */
    /* pt->csPtr,               take it as it is */

    /*
     * Have the transformation reference the new structure containing
     * the saved channel.
     */

    pt->supercedes          = chanPtr;

    /*
     * Don't forget to reinitialize the output buffer used for encodings.
     */

    if ((chanPtr->encoding != NULL) && (chanPtr->flags & TCL_WRITABLE)) {
        chanPtr->outputStage = (char *)
	    ckalloc((unsigned) (chanPtr->bufSize + 2));
    }

    /*
     * Event handling: If the information in the old channel shows
     * that there was interest in some events call the 'WatchProc'
     * of the transformation to establish the proper connection
     * between them.
     */

    if (interest) {
        (pt->typePtr->watchProc) (pt->instanceData, interest);
    }

    /*
     * The superceded channel is effectively unregistered
     * We cannot decrement its reference count because that
     * can cause it to get garbage collected out from under us.
     * Don't add the following code:
     *
     * chanPtr->supercedes->refCount --;
     */

    return (Tcl_Channel) chanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_UnstackChannel --
 *
 *	Unstacks an entry in the hash table for a Tcl_Channel
 *	record. This is the reverse to 'Tcl_StackChannel'.
 *	The old, superceded channel is uncovered and re-registered
 *	in the appropriate data structures.
 *
 * Results:
 *	Returns the old Tcl_Channel, i.e. the one which was stacked over.
 *	A standard Tcl result.
 *
 * Side effects:
 *	If TCL_ERROR is returned, the posix error code will be set
 *	See above.
 *	with Tcl_SetErrno.
 *
 *----------------------------------------------------------------------
 */

void
int
Tcl_UnstackChannel (interp, chan)
    Tcl_Interp* interp; /* The interpreter we are working in */
    Tcl_Interp *interp; /* The interpreter we are working in */
    Tcl_Channel chan;   /* The channel to unstack */
{
    Channel      *chanPtr  = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;
    int result = 0;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    Channel* chanPtr = (Channel*) chan;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    if (chanPtr->supercedes != (Channel*) NULL) {
    if (chanPtr->downChanPtr != (Channel *) NULL) {
        /*
	 * Instead of manipulating the per-thread / per-interp list/hashtable
	 * of registered channels we wind down the state of the transformation,
	 * and then restore the state of underlying channel into the old
	 * structure.
	 */

	Channel *downChanPtr = chanPtr->downChanPtr;
	Tcl_DString       dsTrans; /* storage to save option information */
	Tcl_DString       dsBuf;   /* storage to save option information */
	Channel           top;     /* Save area for current transformation */
	Channel*          chanDownPtr = chanPtr->supercedes;
	int               interest;	/* interest mask of transformation
					 * before destruct. */
	int               saveInputEncodingFlags;  /* Save area for encoding */
 	int               saveOutputEncodingFlags; /* related information */
	Tcl_EncodingState saveInputEncodingState;
	Tcl_EncodingState saveOutputEncodingState;
	Tcl_Encoding      saveEncoding;

	/*
	 * Event handling: Disallow the delivery of events from the
	 * old, now uncovered channel to the transformation.
	 * Flush the buffers. This ensures that any data still in them
	 * at this time _is_ handled by the transformation we are unstacking
	 *
	 * This is done before everything else to avoid problems
	 * after our heavy-duty shuffling of pointers around.
	 * right now. Restrict this to writable channels. Take care to hide
	 * a possible bg-copy in progress from Tcl_Flush and the
	 * CheckForChannelErrors inside.
	 */

	interest = chanPtr->interestMask;
	if (statePtr->flags & TCL_WRITABLE) {
        (chanPtr->typePtr->watchProc) (chanPtr->instanceData, 0);

	    CopyState*    csPtr;
	/* 1. Swap the information in the top channel (the transformation)
	 *    and the channel below, with some exceptions. This additionally
	 *    cuts the top channel out of the chain. Without the latter
	 *    a Tcl_Close on the transformation would be impossible, as that
	 *    procedure will free the structure, making 'top' unusable.
	 *
	 * chanPtr     -> top channel, transformation.

	    csPtr           = statePtr->csPtr;
	 * chanDownPtr -> channel immediately below the transformation.
	 */
	    statePtr->csPtr = (CopyState*) NULL;

	memcpy ((void*) &top,        (void*) chanPtr,     sizeof (Channel));
	memcpy ((void*) chanPtr,     (void*) chanDownPtr, sizeof (Channel));
	top.supercedes = (Channel*) NULL;
	    if (Tcl_Flush((Tcl_Channel) chanPtr) != TCL_OK) {
	        statePtr->csPtr = csPtr;
		Tcl_AppendResult(interp, "could not flush channel \"",
			Tcl_GetChannelName((Tcl_Channel) chanPtr), "\"",
			(char *) NULL);
	memcpy ((void*) chanDownPtr, (void*) &top,        sizeof (Channel));

		return TCL_ERROR;
	    }
	/* Now:
 	 * chanPtr     -> channel immediately below the transformation, now top
 	 * chanDownPtr -> transformation, cut loose.
 	 *
 	 * Handle the exceptions mentioned above, i.e. move the information

	    statePtr->csPtr = csPtr;
 	 * from the transformation into the new top, and reinitialize it to
 	 * safe values in the transformation.
 	 */

	}
	chanPtr->refCount        = chanDownPtr->refCount;
	chanPtr->closeCbPtr      = chanDownPtr->closeCbPtr;
	chanPtr->chPtr           = chanDownPtr->chPtr;
	chanPtr->nextChanPtr     = chanDownPtr->nextChanPtr;
	chanPtr->scriptRecordPtr = chanDownPtr->scriptRecordPtr;
	chanPtr->timer           = chanDownPtr->timer;
	chanPtr->csPtr           = chanDownPtr->csPtr;

	chanDownPtr->refCount        = 0;
	chanDownPtr->closeCbPtr      = (CloseCallback*) NULL;
	chanDownPtr->chPtr           = (ChannelHandler*) NULL;
	chanDownPtr->nextChanPtr     = (Channel*) NULL;
	chanDownPtr->scriptRecordPtr = (EventScriptRecord*) NULL;
	chanDownPtr->timer           = (Tcl_TimerToken) NULL;
	chanDownPtr->csPtr           = (CopyState*) NULL;

	/*
	/* The now uncovered channel still has encoding and eol-translation
	 * deactivated, i.e. switched to 'binary'. *Don't* touch this until
	 * after the transformation is closed for good, as it may write
	 * Anything in the input queue and the push-back buffers of
	 * the transformation going away is transformed data, but not
	 * information into it during that (-> flushing of data waiting in
	 * internal buffers!) and rely on these settings. Thanks to Matt
	 * Newman <matt@sensus.org> for finding this goof.
	 *
	 * But we also have to protect the state of the encoding from removal
	 * yet read. As unstacking means that the caller does not want
	 * to see transformed data any more we have to discard these
	 * during the close. So we save it in some local variables.
	 * Additionally the current value of the options is lost after we
	 * close, we have to save them now.
	 * bytes. To avoid writing an analogue to 'DiscardInputQueued'
	 * we move the information in the push back buffers to the
	 * input queue and then call 'DiscardInputQueued' on that.
	 */

 	saveEncoding            = chanDownPtr->encoding;
 	saveInputEncodingState  = chanDownPtr->inputEncodingState;
 	saveInputEncodingFlags  = chanDownPtr->inputEncodingFlags;
	if (((statePtr->flags & TCL_READABLE)  != 0) &&
	    ((statePtr->inQueueHead != (ChannelBuffer*) NULL) ||
	     (chanPtr->inQueueHead  != (ChannelBuffer*) NULL))) {
 	saveOutputEncodingState = chanDownPtr->outputEncodingState;
 	saveOutputEncodingFlags = chanDownPtr->outputEncodingFlags;

 	Tcl_DStringInit (&dsTrans);
 	Tcl_GetChannelOption (interp, (Tcl_Channel) chanDownPtr,
	    if ((statePtr->inQueueHead != (ChannelBuffer*) NULL) &&
		(chanPtr->inQueueHead  != (ChannelBuffer*) NULL)) {
	        statePtr->inQueueTail->nextPtr = chanPtr->inQueueHead;
		statePtr->inQueueTail = chanPtr->inQueueTail;
	        statePtr->inQueueHead = statePtr->inQueueTail;
		"-translation", &dsTrans);

 	Tcl_DStringInit (&dsBuf);
 	Tcl_GetChannelOption (interp, (Tcl_Channel) chanDownPtr,
		"-buffering", &dsBuf);

	    } else if (chanPtr->inQueueHead != (ChannelBuffer*) NULL) {
	/*
	 * Prevent the accidential removal of the encoding during
	 * the destruction of the transformation channel.
	 */

	        statePtr->inQueueHead = chanPtr->inQueueHead;
	chanDownPtr->encoding            = (Tcl_Encoding) NULL;
	chanDownPtr->inputEncodingState  = (Tcl_EncodingState) NULL;
	chanDownPtr->inputEncodingFlags  = TCL_ENCODING_START;
		statePtr->inQueueTail = chanPtr->inQueueTail;
	chanDownPtr->outputEncodingState = (Tcl_EncodingState) NULL;
	chanDownPtr->outputEncodingFlags = TCL_ENCODING_START;

	    }
	/*
	 * A little trick: Add the transformation structure to the
	 * per-thread list of existing channels (which it never were
	 * part of so far), or Tcl_Close/FlushChannel will panic
	 * ("damaged channel list").
	 *

	 * Afterward do a regular close upon the transformation.
	 * This may cause flushing of data into the old channel (if the
	 * transformation remembered its own channel in itself).
	 *
	    chanPtr->inQueueHead          = (ChannelBuffer*) NULL;
	    chanPtr->inQueueTail          = (ChannelBuffer*) NULL;

	 * We know that its refCount dropped to 0.
	 */

	    DiscardInputQueued (statePtr, 0);
	}
	chanDownPtr->nextChanPtr = tsdPtr->firstChanPtr;
	tsdPtr->firstChanPtr     = chanDownPtr;

	statePtr->topChanPtr	= downChanPtr;
	Tcl_Close (interp, (Tcl_Channel)chanDownPtr);
	downChanPtr->upChanPtr	= (Channel *) NULL;

	/*
	 * Now it is possible to wind down the transformation (in 'top'),
	 * especially to copy the current encoding and translation control
	 * information down.
	 * Leave this link intact for closeproc
	 *  chanPtr->downChanPtr	= (Channel *) NULL;
	 */
	

	/*
	 * Close and free the channel driver state.
	 */
	 * Move the currently active encoding from the save area
	 * to the now uncovered channel. We assume here that this
	 * channel uses 'encoding binary' (==> encoding == NULL, etc.
	 * This allows us to simply copy the pointers without having to
	 * think about refcounts and deallocation of the old encoding.
	 *

	 * And don't forget to reenable the EOL-translation used by the
	 * transformation. Using a DString to do this *is* a bit awkward,
	 * but still the best way to handle the complexities here, like
	 * flag manipulation and event system.
	 */

	if (chanPtr->typePtr->closeProc != TCL_CLOSE2PROC) {
	chanPtr->encoding            = saveEncoding;
	chanPtr->inputEncodingState  = saveInputEncodingState;
	chanPtr->inputEncodingFlags  = saveInputEncodingFlags;
	chanPtr->outputEncodingState = saveOutputEncodingState;
	chanPtr->outputEncodingFlags = saveOutputEncodingFlags;

	Tcl_SetChannelOption (interp, (Tcl_Channel) chanPtr,
	    result = (chanPtr->typePtr->closeProc)(chanPtr->instanceData,
		    interp);
		"-translation", dsTrans.string);

	Tcl_SetChannelOption (interp, (Tcl_Channel) chanPtr,
	} else {
	    result = (chanPtr->typePtr->close2Proc)(chanPtr->instanceData,
		    interp, 0);
		"-buffering", dsBuf.string);

	}
	Tcl_DStringFree (&dsTrans);
	Tcl_DStringFree (&dsBuf);

	chanPtr->typePtr	= NULL;
	/*
	 * Event handling: If the information from the now destroyed
	 * transformation shows that there was interest in some events
	 * call the 'WatchProc' of the now uncovered channel to renew
	 * AK: Tcl_NotifyChannel may hold a reference to this block of memory
	 * that interest with underlying channels or the driver.
	 */

	Tcl_EventuallyFree((ClientData) chanPtr, TCL_DYNAMIC);
	if (interest) {
	    chanPtr->interestMask = 0;
	    (chanPtr->typePtr->watchProc) (chanPtr->instanceData,
		    interest);
	UpdateInterest(downChanPtr);
	    chanPtr->interestMask = interest;
	}


	if (result != 0) {
	    Tcl_SetErrno(result);
	    return TCL_ERROR;
	}
    } else {
        /*
        /* This channel does not cover another one.
	 * This channel does not cover another one.
	 * Simply do a close, if necessary.
	 */

        if (chanPtr->refCount <= 0) {
	    Tcl_Close (interp, chan);
	}
    }
        if (statePtr->refCount <= 0) {
            if (Tcl_Close(interp, chan) != TCL_OK) {
                return TCL_ERROR;
            }
	}
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetStackedChannel --
 *
 *	Determines wether the specified channel is stacked upon another.
 *	Determines whether the specified channel is stacked upon another.
 *
 * Results:
 *	NULL if the channel is not stacked upon another one, or a reference
 *	to the channel it is stacked upon. This reference can be used in
 *	queries, but modification is not allowed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_GetStackedChannel(chan)
    Tcl_Channel chan;
{
    Channel* chanPtr = (Channel*) chan;
    return (Tcl_Channel) chanPtr->supercedes;
    Channel *chanPtr = (Channel *) chan;	/* The actual channel. */

    return (Tcl_Channel) chanPtr->downChanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetTopChannel --
 *
 *	Returns the top channel of a channel stack.
 *
 * Results:
 *	NULL if the channel is not stacked upon another one, or a reference
 *	to the channel it is stacked upon. This reference can be used in
 *	queries, but modification is not allowed.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_GetTopChannel(chan)
    Tcl_Channel chan;
{
    Channel *chanPtr = (Channel *) chan;	/* The actual channel. */

    return (Tcl_Channel) chanPtr->state->topChanPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelInstanceData --
 *
 *	Returns the client data associated with a channel.
 *
 * Results:
 *	The client data.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_GetChannelInstanceData(chan)
    Tcl_Channel chan;		/* Channel for which to return client data. */
{
    Channel *chanPtr = (Channel *) chan;	/* The actual channel. */

    return chanPtr->instanceData;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelType --
 *
 *	Given a channel structure, returns the channel type structure.
 *
 * Results:
 *	Returns a pointer to the channel type structure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_ChannelType *
Tcl_GetChannelType(chan)
    Tcl_Channel chan;		/* The channel to return type for. */
{
    Channel *chanPtr = (Channel *) chan;	/* The actual channel. */

    return chanPtr->typePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelMode --
 *

 */

int
Tcl_GetChannelMode(chan)
    Tcl_Channel chan;		/* The channel for which the mode is
                                 * being computed. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
    Channel *chanPtr;		/* The actual channel. */
					/* State of actual channel. */

    chanPtr = (Channel *) chan;
    return (chanPtr->flags & (TCL_READABLE | TCL_WRITABLE));
    return (statePtr->flags & (TCL_READABLE | TCL_WRITABLE));
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelName --
 *

 *----------------------------------------------------------------------
 */

char *
Tcl_GetChannelName(chan)
    Tcl_Channel chan;		/* The channel for which to return the name. */
{
    Channel *chanPtr;		/* The actual channel. */
    ChannelState *statePtr;	/* State of actual channel. */

    chanPtr = (Channel *) chan;
    return chanPtr->channelName;
    statePtr = ((Channel *) chan)->state;
    return statePtr->channelName;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelType --
 *
 *	Given a channel structure, returns the channel type structure.
 *
 * Results:
 *	Returns a pointer to the channel type structure.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

Tcl_ChannelType *
Tcl_GetChannelType(chan)
    Tcl_Channel chan;		/* The channel to return type for. */
{
    Channel *chanPtr;		/* The actual channel. */

    chanPtr = (Channel *) chan;
    return chanPtr->typePtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelHandle --
 *

    int direction;		/* TCL_WRITABLE or TCL_READABLE. */
    ClientData *handlePtr;	/* Where to store handle */
{
    Channel *chanPtr;		/* The actual channel. */
    ClientData handle;
    int result;

    chanPtr = (Channel *) chan;
    chanPtr = ((Channel *) chan)->state->bottomChanPtr;
    result = (chanPtr->typePtr->getHandleProc)(chanPtr->instanceData,
	    direction, &handle);
    if (handlePtr) {
	*handlePtr = handle;
    }
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelInstanceData --
 *
 *	Returns the client data associated with a channel.
 *
 * Results:
 *	The client data.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

ClientData
Tcl_GetChannelInstanceData(chan)
    Tcl_Channel chan;		/* Channel for which to return client data. */
{
    Channel *chanPtr;		/* The actual channel. */

    chanPtr = (Channel *) chan;
    return chanPtr->instanceData;
}

/*
 *---------------------------------------------------------------------------
 *
 * AllocChannelBuffer --
 *
 *	A channel buffer has BUFFER_PADDING bytes extra at beginning to

 * Side effects:
 *	May free a buffer to the OS.
 *
 *----------------------------------------------------------------------
 */

static void
RecycleBuffer(chanPtr, bufPtr, mustDiscard)
    Channel *chanPtr;		/* Channel for which to recycle buffers. */
RecycleBuffer(statePtr, bufPtr, mustDiscard)
    ChannelState *statePtr;	/* ChannelState in which to recycle buffers. */
    ChannelBuffer *bufPtr;	/* The buffer to recycle. */
    int mustDiscard;		/* If nonzero, free the buffer to the
                                 * OS, always. */
{
    /*
     * Do we have to free the buffer to the OS?
     */

    if (mustDiscard) {
        ckfree((char *) bufPtr);
        return;
    }
    

    /*
     * Only save buffers for the input queue if the channel is readable.
     */
    
    if (chanPtr->flags & TCL_READABLE) {
        if (chanPtr->inQueueHead == (ChannelBuffer *) NULL) {
            chanPtr->inQueueHead = bufPtr;
            chanPtr->inQueueTail = bufPtr;
    if (statePtr->flags & TCL_READABLE) {
        if (statePtr->inQueueHead == (ChannelBuffer *) NULL) {
            statePtr->inQueueHead = bufPtr;
            statePtr->inQueueTail = bufPtr;
            goto keepit;
        }
        if (chanPtr->saveInBufPtr == (ChannelBuffer *) NULL) {
            chanPtr->saveInBufPtr = bufPtr;
        if (statePtr->saveInBufPtr == (ChannelBuffer *) NULL) {
            statePtr->saveInBufPtr = bufPtr;
            goto keepit;
        }
    }

    /*
     * Only save buffers for the output queue if the channel is writable.
     */

    if (chanPtr->flags & TCL_WRITABLE) {
        if (chanPtr->curOutPtr == (ChannelBuffer *) NULL) {
            chanPtr->curOutPtr = bufPtr;
    if (statePtr->flags & TCL_WRITABLE) {
        if (statePtr->curOutPtr == (ChannelBuffer *) NULL) {
            statePtr->curOutPtr = bufPtr;
            goto keepit;
        }
    }

    /*
     * If we reached this code we return the buffer to the OS.
     */

 * Side effects:
 *	Recycles buffers.
 *
 *----------------------------------------------------------------------
 */

static void
DiscardOutputQueued(chanPtr)
    Channel *chanPtr;		/* The channel for which to discard output. */
DiscardOutputQueued(statePtr)
    ChannelState *statePtr;	/* ChannelState for which to discard output. */
{
    ChannelBuffer *bufPtr;
    
    while (chanPtr->outQueueHead != (ChannelBuffer *) NULL) {
        bufPtr = chanPtr->outQueueHead;
        chanPtr->outQueueHead = bufPtr->nextPtr;
        RecycleBuffer(chanPtr, bufPtr, 0);
    while (statePtr->outQueueHead != (ChannelBuffer *) NULL) {
        bufPtr = statePtr->outQueueHead;
        statePtr->outQueueHead = bufPtr->nextPtr;
        RecycleBuffer(statePtr, bufPtr, 0);
    }
    chanPtr->outQueueHead = (ChannelBuffer *) NULL;
    chanPtr->outQueueTail = (ChannelBuffer *) NULL;
    statePtr->outQueueHead = (ChannelBuffer *) NULL;
    statePtr->outQueueTail = (ChannelBuffer *) NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * CheckForDeadChannel --
 *
 *	This function checks is a given channel is Dead.
 *      (A channel that has been closed but not yet deallocated.)
 *
 * Results:
 *	True (1) if channel is Dead, False (0) if channel is Ok
 *
 * Side effects:
 *      None
 *
 *----------------------------------------------------------------------
 */

static int
CheckForDeadChannel(interp, chanPtr)
CheckForDeadChannel(interp, statePtr)
    Tcl_Interp *interp;		/* For error reporting (can be NULL) */
    Channel    *chanPtr;	/* The channel to check. */
    ChannelState *statePtr;	/* The channel state to check. */
{
    if (chanPtr->flags & CHANNEL_DEAD) {
    if (statePtr->flags & CHANNEL_DEAD) {
        Tcl_SetErrno(EINVAL);
	if (interp) {
	    Tcl_AppendResult(interp,
		    "unable to access channel: invalid channel",
		    (char *) NULL);   
	}
	return 1;

FlushChannel(interp, chanPtr, calledFromAsyncFlush)
    Tcl_Interp *interp;			/* For error reporting during close. */
    Channel *chanPtr;			/* The channel to flush on. */
    int calledFromAsyncFlush;		/* If nonzero then we are being
                                         * called from an asynchronous
                                         * flush callback. */
{
    ChannelState *statePtr = chanPtr->state;
					/* State of the channel stack. */
    ChannelBuffer *bufPtr;		/* Iterates over buffered output
                                         * queue. */
    int toWrite;			/* Amount of output data in current
                                         * buffer available to be written. */
    int written;			/* Amount of output data actually
                                         * written in current round. */
    int errorCode = 0;			/* Stores POSIX error codes from
                                         * channel driver operations. */
    int wroteSome;			/* Set to one if any data was
    int wroteSome = 0;			/* Set to one if any data was
					 * written to the driver. */

    restartFlushChannel:
    wroteSome = 0;

    /*
     * Prevent writing on a dead channel -- a channel that has been closed
     * but not yet deallocated. This can occur if the exit handler for the
     * channel deallocation runs before all channels are deregistered in
     * all interpreters.
     */
    
    if (CheckForDeadChannel(interp,chanPtr)) return -1;
    if (CheckForDeadChannel(interp, statePtr)) return -1;
    
    /*
     * Loop over the queued buffers and attempt to flush as
     * much as possible of the queued output to the channel.
     */

    while (1) {

        /*
         * If the queue is empty and there is a ready current buffer, OR if
         * the current buffer is full, then move the current buffer to the
         * queue.
         */
        
        if (((chanPtr->curOutPtr != (ChannelBuffer *) NULL) &&
                (chanPtr->curOutPtr->nextAdded == chanPtr->curOutPtr->bufLength))
                || ((chanPtr->flags & BUFFER_READY) &&
                        (chanPtr->outQueueHead == (ChannelBuffer *) NULL))) {
            chanPtr->flags &= (~(BUFFER_READY));
            chanPtr->curOutPtr->nextPtr = (ChannelBuffer *) NULL;
            if (chanPtr->outQueueHead == (ChannelBuffer *) NULL) {
                chanPtr->outQueueHead = chanPtr->curOutPtr;

        if (((statePtr->curOutPtr != (ChannelBuffer *) NULL) &&
                (statePtr->curOutPtr->nextAdded == statePtr->curOutPtr->bufLength))
                || ((statePtr->flags & BUFFER_READY) &&
                        (statePtr->outQueueHead == (ChannelBuffer *) NULL))) {
            statePtr->flags &= (~(BUFFER_READY));
            statePtr->curOutPtr->nextPtr = (ChannelBuffer *) NULL;
            if (statePtr->outQueueHead == (ChannelBuffer *) NULL) {
                statePtr->outQueueHead = statePtr->curOutPtr;
            } else {
                chanPtr->outQueueTail->nextPtr = chanPtr->curOutPtr;
                statePtr->outQueueTail->nextPtr = statePtr->curOutPtr;
            }
            chanPtr->outQueueTail = chanPtr->curOutPtr;
            chanPtr->curOutPtr = (ChannelBuffer *) NULL;
            statePtr->outQueueTail = statePtr->curOutPtr;
            statePtr->curOutPtr = (ChannelBuffer *) NULL;
        }
        bufPtr = chanPtr->outQueueHead;
        bufPtr = statePtr->outQueueHead;

        /*
         * If we are not being called from an async flush and an async
         * flush is active, we just return without producing any output.
         */

        if ((!calledFromAsyncFlush) &&
                (chanPtr->flags & BG_FLUSH_SCHEDULED)) {
                (statePtr->flags & BG_FLUSH_SCHEDULED)) {
            return 0;
        }

        /*
         * If the output queue is still empty, break out of the while loop.
         */

        if (bufPtr == (ChannelBuffer *) NULL) {
            break;	/* Out of the "while (1)". */
        }

        /*
         * Produce the output on the channel.
         */
        

        toWrite = bufPtr->nextAdded - bufPtr->nextRemoved;
        written = (chanPtr->typePtr->outputProc) (chanPtr->instanceData,
                (char *) bufPtr->buf + bufPtr->nextRemoved, toWrite,
		&errorCode);
            

	/*
         * If the write failed completely attempt to start the asynchronous
         * flush mechanism and break out of this loop - do not attempt to
         * write any more output at this time.
         */

        if (written < 0) {

            if ((errorCode == EWOULDBLOCK) || (errorCode == EAGAIN)) {
		/*
		 * This used to check for CHANNEL_NONBLOCKING, and panic
		 * if the channel was blocking.  However, it appears
		 * that setting stdin to -blocking 0 has some effect on
		 * the stdout when it's a tty channel (dup'ed underneath)
		 */
		if (!(chanPtr->flags & BG_FLUSH_SCHEDULED)) {
		    chanPtr->flags |= BG_FLUSH_SCHEDULED;
		if (!(statePtr->flags & BG_FLUSH_SCHEDULED)) {
		    statePtr->flags |= BG_FLUSH_SCHEDULED;
		    UpdateInterest(chanPtr);
		}
		errorCode = 0;
		break;
            }

            /*
             * Decide whether to report the error upwards or defer it.
             */

            if (calledFromAsyncFlush) {
                if (chanPtr->unreportedError == 0) {
                    chanPtr->unreportedError = errorCode;
                if (statePtr->unreportedError == 0) {
                    statePtr->unreportedError = errorCode;
                }
            } else {
                Tcl_SetErrno(errorCode);
		if (interp != NULL) {
		    Tcl_SetResult(interp,
			    Tcl_PosixError(interp), TCL_VOLATILE);
		}
            }

            /*
             * When we get an error we throw away all the output
             * currently queued.
             */

            DiscardOutputQueued(chanPtr);
            DiscardOutputQueued(statePtr);
            continue;
        } else {
	    wroteSome = 1;
	}

        bufPtr->nextRemoved += written;

        /*
         * If this buffer is now empty, recycle it.
         */

        if (bufPtr->nextRemoved == bufPtr->nextAdded) {
            chanPtr->outQueueHead = bufPtr->nextPtr;
            if (chanPtr->outQueueHead == (ChannelBuffer *) NULL) {
                chanPtr->outQueueTail = (ChannelBuffer *) NULL;
            statePtr->outQueueHead = bufPtr->nextPtr;
            if (statePtr->outQueueHead == (ChannelBuffer *) NULL) {
                statePtr->outQueueTail = (ChannelBuffer *) NULL;
            }
            RecycleBuffer(chanPtr, bufPtr, 0);
            RecycleBuffer(statePtr, bufPtr, 0);
        }
    }	/* Closes "while (1)". */

    /*
     * If we wrote some data while flushing in the background, we are done.
     * We can't finish the background flush until we run out of data and
     * the channel becomes writable again.  This ensures that all of the
     * pending data has been flushed at the system level.
     */

    if (chanPtr->flags & BG_FLUSH_SCHEDULED) {
    if (statePtr->flags & BG_FLUSH_SCHEDULED) {
	if (wroteSome) {
	    return errorCode;
	} else if (chanPtr->outQueueHead == (ChannelBuffer *) NULL) {
	    chanPtr->flags &= (~(BG_FLUSH_SCHEDULED));
	} else if (statePtr->outQueueHead == (ChannelBuffer *) NULL) {
	    statePtr->flags &= (~(BG_FLUSH_SCHEDULED));
	    (chanPtr->typePtr->watchProc)(chanPtr->instanceData,
		    chanPtr->interestMask);
		    statePtr->interestMask);
	}
    }

    /*
     * If the channel is flagged as closed, delete it when the refCount
     * drops to zero, the output queue is empty and there is no output
     * in the current output buffer.
     */

    if ((chanPtr->flags & CHANNEL_CLOSED) && (chanPtr->refCount <= 0) &&
            (chanPtr->outQueueHead == (ChannelBuffer *) NULL) &&
            ((chanPtr->curOutPtr == (ChannelBuffer *) NULL) ||
                    (chanPtr->curOutPtr->nextAdded ==
                            chanPtr->curOutPtr->nextRemoved))) {
    if ((statePtr->flags & CHANNEL_CLOSED) && (statePtr->refCount <= 0) &&
            (statePtr->outQueueHead == (ChannelBuffer *) NULL) &&
            ((statePtr->curOutPtr == (ChannelBuffer *) NULL) ||
                    (statePtr->curOutPtr->nextAdded ==
                            statePtr->curOutPtr->nextRemoved))) {
	/*
	 * CloseChannel may side-effect the errno value, so we seed it
	 * and retrieve the it once we have closed the final channel.
	 */
	Tcl_SetErrno(errorCode);
	if (CloseChannel(interp, chanPtr, errorCode)) {
	return CloseChannel(interp, chanPtr, errorCode);
	    goto restartFlushChannel;
	}
	errorCode = Tcl_GetErrno();
    }
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *

CloseChannel(interp, chanPtr, errorCode)
    Tcl_Interp *interp;			/* For error reporting. */
    Channel *chanPtr;			/* The channel to close. */
    int errorCode;			/* Status of operation so far. */
{
    int result = 0;			/* Of calling driver close
                                         * operation. */
    Channel *prevChanPtr;		/* Preceding channel in list of
                                         * all channels - used to splice a
    ChannelState *prevCSPtr;		/* Preceding channel state in list of
                                         * all states - used to splice a
                                         * channel out of the list on close. */
    ChannelState *statePtr;		/* state of the channel stack. */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (chanPtr == NULL) {
        return result;
    }
    statePtr = chanPtr->state;
    

    /*
     * No more input can be consumed so discard any leftover input.
     */

    DiscardInputQueued(chanPtr, 1);
    DiscardInputQueued(statePtr, 1);

    /*
     * Discard a leftover buffer in the current output buffer field.
     */

    if (chanPtr->curOutPtr != (ChannelBuffer *) NULL) {
        ckfree((char *) chanPtr->curOutPtr);
        chanPtr->curOutPtr = (ChannelBuffer *) NULL;
    if (statePtr->curOutPtr != (ChannelBuffer *) NULL) {
        ckfree((char *) statePtr->curOutPtr);
        statePtr->curOutPtr = (ChannelBuffer *) NULL;
    }
    
    /*
     * The caller guarantees that there are no more buffers
     * queued for output.
     */

    if (chanPtr->outQueueHead != (ChannelBuffer *) NULL) {
    if (statePtr->outQueueHead != (ChannelBuffer *) NULL) {
        panic("TclFlush, closed channel: queued output left");
    }

    /*
     * If the EOF character is set in the channel, append that to the
     * output device.
     */

    if ((chanPtr->outEofChar != 0) && (chanPtr->flags & TCL_WRITABLE)) {
    if ((statePtr->outEofChar != 0) && (statePtr->flags & TCL_WRITABLE)) {
        int dummy;
        char c;

        c = (char) chanPtr->outEofChar;
        c = (char) statePtr->outEofChar;
        (chanPtr->typePtr->outputProc) (chanPtr->instanceData, &c, 1, &dummy);
    }

#if 0
    /*
     * Remove TCL_READABLE and TCL_WRITABLE from chanPtr->flags, so
     * Remove TCL_READABLE and TCL_WRITABLE from statePtr->flags, so
     * that close callbacks can not do input or output (assuming they
     * squirreled the channel away in their clientData). This also
     * prevents infinite loops if the callback calls any C API that
     * could call FlushChannel.
     */

    /*
     * This prevents any data from being flushed from stacked channels.
     */
    chanPtr->flags &= (~(TCL_READABLE|TCL_WRITABLE));
    statePtr->flags &= (~(TCL_READABLE|TCL_WRITABLE));
#endif

    /*
     * Splice this channel out of the list of all channels.
     */

    if (chanPtr == tsdPtr->firstChanPtr) {
        tsdPtr->firstChanPtr = chanPtr->nextChanPtr;
    if (tsdPtr->firstCSPtr && (statePtr == tsdPtr->firstCSPtr)) {
        tsdPtr->firstCSPtr = statePtr->nextCSPtr;
    } else {
        for (prevChanPtr = tsdPtr->firstChanPtr;
	     prevChanPtr && (prevChanPtr->nextChanPtr != chanPtr);
	     prevChanPtr = prevChanPtr->nextChanPtr) {
        for (prevCSPtr = tsdPtr->firstCSPtr;
	     prevCSPtr && (prevCSPtr->nextCSPtr != statePtr);
	     prevCSPtr = prevCSPtr->nextCSPtr) {
            /* Empty loop body. */
        }
        if (prevChanPtr == (Channel *) NULL) {
        if (prevCSPtr == (ChannelState *) NULL) {
            panic("FlushChannel: damaged channel list");
        }
        prevChanPtr->nextChanPtr = chanPtr->nextChanPtr;
        prevCSPtr->nextCSPtr = statePtr->nextCSPtr;
    }

    /*
     * Close and free the channel driver state.
     */
            

    if (chanPtr->typePtr->closeProc != TCL_CLOSE2PROC) {
	result = (chanPtr->typePtr->closeProc)(chanPtr->instanceData, interp);
    } else {
	result = (chanPtr->typePtr->close2Proc)(chanPtr->instanceData, interp,
		0);
    }
    
    if (chanPtr->channelName != (char *) NULL) {
        ckfree(chanPtr->channelName);

    /*
     * Some resources can be cleared only if the bottom channel
     * in a stack is closed. All the other channels in the stack
     * are not allowed to remove.
     */

    if (chanPtr == statePtr->bottomChanPtr) {
	if (statePtr->channelName != (char *) NULL) {
	    ckfree(statePtr->channelName);
	    statePtr->channelName = NULL;
	}

	Tcl_FreeEncoding(statePtr->encoding);
	if (statePtr->outputStage != NULL) {
	    ckfree((char *) statePtr->outputStage);
	    statePtr->outputStage = (char *) NULL;
	}
    }

    /*
     * If we are being called synchronously, report either
     * any latent error on the channel or the current error.
     */

    if (chanPtr->unreportedError != 0) {
        errorCode = chanPtr->unreportedError;
    if (statePtr->unreportedError != 0) {
        errorCode = statePtr->unreportedError;
    }
    if (errorCode == 0) {
        errorCode = result;
        if (errorCode != 0) {
            Tcl_SetErrno(errorCode);
        }
    }

    /*
     * Cancel any outstanding timer.
     */

    Tcl_DeleteTimerHandler(chanPtr->timer);
    Tcl_DeleteTimerHandler(statePtr->timer);

    /*
     * Mark the channel as deleted by clearing the type structure.
     */

    if (chanPtr->supercedes != (Channel *) NULL) {
    if (chanPtr->downChanPtr != (Channel *) NULL) {
        /*
	 * Unwind the state of the transformation, and then restore the state
	 * of (unstack) the underlying channel into the TOP channel structure.
	 */

#if 0
	ChannelHandler *chPtr, *chNext;	/* Iterate over channel handlers. */
	NextChannelHandler *nhPtr;
	Channel *chanDownPtr = chanPtr->supercedes;

	int code = TCL_OK;
	/*
	 * Insert ourselves upon back into the list of open channels,
	 * because we are only eliminating the NEXT channel in the stack.
	 */
	chanPtr->nextChanPtr = tsdPtr->firstChanPtr;
	tsdPtr->firstChanPtr = chanPtr;

	/*
	 * Some initial bits taken from Tcl_Close, to be applied to our
	 * underlying channel.
	 */

	/*
	while (chanPtr->downChanPtr != (Channel *) NULL) {
	    /*
	 * Remove any references to channel handlers for this channel that
	 * may be about to be invoked.
	 */

	     * Unwind the state of the transformation, and then restore the
	for (nhPtr = tsdPtr->nestedHandlerPtr;
             nhPtr != (NextChannelHandler *) NULL;
             nhPtr = nhPtr->nestedHandlerPtr) {
	    if (nhPtr->nextHandlerPtr &&
		    (nhPtr->nextHandlerPtr->chanPtr == chanDownPtr)) {
		nhPtr->nextHandlerPtr = NULL;
	    }
	}

	     * state of (unstack) the underlying channel into the TOP channel
	/*
	 * Remove all the channel handler records attached to the channel
	 * itself.
	 */
        
	     * structure.
	for (chPtr = chanDownPtr->chPtr; chPtr != NULL; chPtr = chNext) {
	    chNext = chPtr->nextPtr;
	    ckfree((char *) chPtr);
	}
	chanDownPtr->chPtr = (ChannelHandler *) NULL;

	/*
	 * Cancel any pending copy operation.
	 */

	StopCopy(chanDownPtr->csPtr);
  
	/*
	 * Ensure that the last output buffer will be flushed.
	 */
    
	if ((chanDownPtr->curOutPtr != (ChannelBuffer *) NULL) &&
		(chanDownPtr->curOutPtr->nextAdded >
			chanDownPtr->curOutPtr->nextRemoved)) {
	    chanDownPtr->flags |= BUFFER_READY;
	}

	/*
	 * Free timer associated with the TOP stacked channel, and
	 * moving the timer for the NEXT stacked channel to the TOP.
	 */
	     */
	if (chanDownPtr->timer != NULL) {
	    Tcl_DeleteTimerHandler(chanDownPtr->timer);
	    chanPtr->timer = Tcl_CreateTimerHandler(0, ChannelTimerProc,
		    (ClientData) chanPtr);
	    code = Tcl_UnstackChannel(interp, (Tcl_Channel) chanPtr);
	} else {
	    chanPtr->timer = NULL;
	}

	    if (code == TCL_ERROR) {
	/*
	 * Bring the information from the NEXT channel into the TOP
	 * channel, with some exceptions. This additionally
	 * cuts the NEXT channel out of the chain and frees it.
	 *
	 * We may want to extract unreportedError as well (hobbs).
	 */

		errorCode = Tcl_GetErrno();
	chanPtr->channelName	= chanDownPtr->channelName;
	chanPtr->flags		= chanDownPtr->flags | CHANNEL_CLOSED;

		break;
	Tcl_FreeEncoding(chanDownPtr->encoding);
	chanDownPtr->encoding	= NULL;

	    }
	chanPtr->instanceData	= chanDownPtr->instanceData;
	chanPtr->typePtr	= chanDownPtr->typePtr;

	    chanPtr = chanPtr->downChanPtr;
	if (chanDownPtr->outputStage != NULL) {
	    ckfree((char *) chanDownPtr->outputStage);
	}

	chanPtr->curOutPtr	= chanDownPtr->curOutPtr;
#else
	Channel *downChanPtr = chanPtr->downChanPtr;
	chanPtr->outQueueHead	= chanDownPtr->outQueueHead;
	chanPtr->outQueueTail	= chanDownPtr->outQueueTail;
	chanPtr->saveInBufPtr	= chanDownPtr->saveInBufPtr;
	chanPtr->inQueueHead	= chanDownPtr->inQueueHead;
	chanPtr->inQueueTail	= chanDownPtr->inQueueTail;
	chanPtr->supercedes	= chanDownPtr->supercedes;

	/*
	 * Event handling: If the information from the now destroyed
	 * transformation shows that there was interest in some events
	 * call the 'WatchProc' of the now uncovered channel to renew
	 * that interest with underlying channels or the driver.
	 */

	statePtr->nextCSPtr	= tsdPtr->firstCSPtr;
	if (chanDownPtr->interestMask) {
	    int interest = chanDownPtr->interestMask;

	tsdPtr->firstCSPtr	= statePtr;
	    chanPtr->interestMask = 0;
	    (chanPtr->typePtr->watchProc)(chanPtr->instanceData, interest);
	    chanPtr->interestMask = interest;
	}


	statePtr->topChanPtr	= downChanPtr;
	Tcl_EventuallyFree((ClientData) chanDownPtr, TCL_DYNAMIC);
	return 1;
    } else {
	/*
	 * There is only the TOP Channel, so we free the remaining
	downChanPtr->upChanPtr	= (Channel *) NULL;
	 * pointers we have and then ourselves.
	 */
	chanPtr->typePtr = NULL;
	chanPtr->typePtr	= NULL;

	Tcl_FreeEncoding(chanPtr->encoding);
	if (chanPtr->outputStage != NULL) {
	    ckfree((char *) chanPtr->outputStage);
	}

	Tcl_EventuallyFree((ClientData) chanPtr, TCL_DYNAMIC);
	return 0;
	return Tcl_Close(interp, (Tcl_Channel) downChanPtr);
#endif
    }

    /*
     * There is only the TOP Channel, so we free the remaining
     * pointers we have and then ourselves.
     */
    chanPtr->typePtr = NULL;

    Tcl_EventuallyFree((ClientData) chanPtr, TCL_DYNAMIC);

    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_Close --
 *

                                         * interpreter. */
{
    ChannelHandler *chPtr, *chNext;	/* Iterate over channel handlers. */
    CloseCallback *cbPtr;		/* Iterate over close callbacks
                                         * for this channel. */
    EventScriptRecord *ePtr, *eNextPtr;	/* Iterate over eventscript records. */
    Channel *chanPtr;			/* The real IO channel. */
    ChannelState *statePtr;		/* State of real IO channel. */
    int result;				/* Of calling FlushChannel. */
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    NextChannelHandler *nhPtr;

    if (chan == (Tcl_Channel) NULL) {
        return TCL_OK;
    }
    

    /*
     * Perform special handling for standard channels being closed. If the
     * refCount is now 1 it means that the last reference to the standard
     * channel is being explicitly closed, so bump the refCount down
     * artificially to 0. This will ensure that the channel is actually
     * closed, below. Also set the static pointer to NULL for the channel.
     */

    CheckForStdChannelsBeingClosed(chan);

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = (Channel *) chan;
    if (chanPtr->refCount > 0) {
    chanPtr	= (Channel *) chan;
    statePtr	= chanPtr->state;
    chanPtr	= statePtr->topChanPtr;

    if (statePtr->refCount > 0) {
        panic("called Tcl_Close on channel with refCount > 0");
    }

    /*
     * Remove any references to channel handlers for this channel that
     * may be about to be invoked.
     */

        }
    }

    /*
     * Remove all the channel handler records attached to the channel
     * itself.
     */
        
    for (chPtr = chanPtr->chPtr;

    for (chPtr = statePtr->chPtr;
	 chPtr != (ChannelHandler *) NULL;
	 chPtr = chNext) {
        chNext = chPtr->nextPtr;
        ckfree((char *) chPtr);
    }
    chanPtr->chPtr = (ChannelHandler *) NULL;
    
    statePtr->chPtr = (ChannelHandler *) NULL;

    
    /*
     * Cancel any pending copy operation.
     */

    StopCopy(chanPtr->csPtr);
    StopCopy(statePtr->csPtr);

    /*
     * Must set the interest mask now to 0, otherwise infinite loops
     * will occur if Tcl_DoOneEvent is called before the channel is
     * finally deleted in FlushChannel. This can happen if the channel
     * has a background flush active.
     */
        
    chanPtr->interestMask = 0;
    statePtr->interestMask = 0;
    
    /*
     * Remove any EventScript records for this channel.
     */

    for (ePtr = chanPtr->scriptRecordPtr;
    for (ePtr = statePtr->scriptRecordPtr;
	 ePtr != (EventScriptRecord *) NULL;
	 ePtr = eNextPtr) {
        eNextPtr = ePtr->nextPtr;
	Tcl_DecrRefCount(ePtr->scriptPtr);
        ckfree((char *) ePtr);
    }
    chanPtr->scriptRecordPtr = (EventScriptRecord *) NULL;
    statePtr->scriptRecordPtr = (EventScriptRecord *) NULL;
        
    /*
     * Invoke the registered close callbacks and delete their records.
     */

    while (chanPtr->closeCbPtr != (CloseCallback *) NULL) {
        cbPtr = chanPtr->closeCbPtr;
        chanPtr->closeCbPtr = cbPtr->nextPtr;
    while (statePtr->closeCbPtr != (CloseCallback *) NULL) {
        cbPtr = statePtr->closeCbPtr;
        statePtr->closeCbPtr = cbPtr->nextPtr;
        (cbPtr->proc) (cbPtr->clientData);
        ckfree((char *) cbPtr);
    }

    /*
     * Ensure that the last output buffer will be flushed.
     */
    
    if ((chanPtr->curOutPtr != (ChannelBuffer *) NULL) &&
	    (chanPtr->curOutPtr->nextAdded > chanPtr->curOutPtr->nextRemoved)) {
        chanPtr->flags |= BUFFER_READY;
    if ((statePtr->curOutPtr != (ChannelBuffer *) NULL) &&
	    (statePtr->curOutPtr->nextAdded > statePtr->curOutPtr->nextRemoved)) {
        statePtr->flags |= BUFFER_READY;
    }

    /*
     * If this channel supports it, close the read side, since we don't need it
     * anymore and this will help avoid deadlocks on some channel types.
     */

    if (chanPtr->typePtr->closeProc == TCL_CLOSE2PROC) {
	result = (chanPtr->typePtr->close2Proc)(chanPtr->instanceData, interp,
		TCL_CLOSE_READ);
    } else {
	result = 0;
    }

    /*
     * The call to FlushChannel will flush any queued output and invoke
     * the close function of the channel driver, or it will set up the
     * channel to be flushed and closed asynchronously.
     */

    chanPtr->flags |= CHANNEL_CLOSED;
    statePtr->flags |= CHANNEL_CLOSED;
    if ((FlushChannel(interp, chanPtr, 0) != 0) || (result != 0)) {
        return TCL_ERROR;
    }
    return TCL_OK;
}

/*

int
Tcl_Write(chan, src, srcLen)
    Tcl_Channel chan;			/* The channel to buffer output for. */
    char *src;				/* Data to queue in output buffer. */
    int srcLen;				/* Length of data in bytes, or < 0 for
					 * strlen(). */
{
    /*
     * Always use the topmost channel of the stack
     */
    Channel *chanPtr;
    ChannelState *statePtr;	/* state info for channel */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_WRITABLE) != 0) {
    statePtr = ((Channel *) chan)->state;
    chanPtr  = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }

    if (srcLen < 0) {
        srcLen = strlen(src);
    }
    return DoWrite(chanPtr, src, srcLen);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_WriteRaw --
 *
 *	Puts a sequence of bytes into an output buffer, may queue the
 *	buffer for output if it gets full, and also remembers whether the
 *	current buffer is ready e.g. if it contains a newline and we are in
 *	line buffering mode.
 *
 * Results:
 *	The number of bytes written or -1 in case of error. If -1,
 *	Tcl_GetErrno will return the error code.
 *
 * Side effects:
 *	May buffer up output and may cause output to be produced on the
 *	channel.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_WriteRaw(chan, src, srcLen)
    Tcl_Channel chan;			/* The channel to buffer output for. */
    char *src;				/* Data to queue in output buffer. */
    int srcLen;				/* Length of data in bytes, or < 0 for
					 * strlen(). */
{
    Channel *chanPtr = ((Channel *) chan);
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    int errorCode, written;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE | CHANNEL_RAW_MODE) != 0) {
	return -1;
    }

    if (srcLen < 0) {
        srcLen = strlen(src);
    }

    /*
     * Go immediately to the driver, do all the error handling by ourselves.
     * The code was stolen from 'FlushChannel'.
     */

    written = (chanPtr->typePtr->outputProc) (chanPtr->instanceData,
	    src, srcLen, &errorCode);

    if (written < 0) {
	Tcl_SetErrno(errorCode);
    }

    return written;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_WriteChars --
 *
 *	Takes a sequence of UTF-8 characters and converts them for output

int
Tcl_WriteChars(chan, src, len)
    Tcl_Channel chan;		/* The channel to buffer output for. */
    CONST char *src;		/* UTF-8 characters to queue in output buffer. */
    int len;			/* Length of string in bytes, or < 0 for 
				 * strlen(). */
{
    /*
     * Always use the topmost channel of the stack
     */
    Channel *chanPtr;
    ChannelState *statePtr;	/* state info for channel */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_WRITABLE) != 0) {
    statePtr = ((Channel *) chan)->state;
    chanPtr  = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }
    if (len < 0) {
        len = strlen(src);
    }
    if (chanPtr->encoding == NULL) {
    if (statePtr->encoding == NULL) {
	/*
	 * Inefficient way to convert UTF-8 to byte-array, but the  
	 * code parallels the way it is done for objects.
	 */

	Tcl_Obj *objPtr;
	int result;

 */

int
Tcl_WriteObj(chan, objPtr)
    Tcl_Channel chan;		/* The channel to buffer output for. */
    Tcl_Obj *objPtr;		/* The object to write. */
{
    /*
     * Always use the topmost channel of the stack
     */
    Channel *chanPtr;
    ChannelState *statePtr;	/* state info for channel */
    char *src;
    int srcLen;

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_WRITABLE) != 0) {
    statePtr = ((Channel *) chan)->state;
    chanPtr  = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }
    if (chanPtr->encoding == NULL) {
    if (statePtr->encoding == NULL) {
	src = (char *) Tcl_GetByteArrayFromObj(objPtr, &srcLen);
	return WriteBytes(chanPtr, src, srcLen);
    } else {
	src = Tcl_GetStringFromObj(objPtr, &srcLen);
	return WriteChars(chanPtr, src, srcLen);
    }
}

static int
WriteBytes(chanPtr, src, srcLen)
    Channel *chanPtr;		/* The channel to buffer output for. */
    CONST char *src;		/* Bytes to write. */
    int srcLen;			/* Number of bytes to write. */
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    char *dst;
    int dstLen, dstMax, sawLF, savedLF, total, toWrite;
    
    total = 0;
    sawLF = 0;
    savedLF = 0;

    /*
     * Loop over all bytes in src, storing them in output buffer with
     * proper EOL translation.
     */

    while (srcLen + savedLF > 0) {
	bufPtr = chanPtr->curOutPtr;
	bufPtr = statePtr->curOutPtr;
	if (bufPtr == NULL) {
	    bufPtr = AllocChannelBuffer(chanPtr->bufSize);
	    chanPtr->curOutPtr	= bufPtr;
	    bufPtr = AllocChannelBuffer(statePtr->bufSize);
	    statePtr->curOutPtr	= bufPtr;
	}
	dst = bufPtr->buf + bufPtr->nextAdded;
	dstMax = bufPtr->bufLength - bufPtr->nextAdded;
	dstLen = dstMax;

	toWrite = dstLen;
	if (toWrite > srcLen) {

	     * line-based, we will need to flush it.
	     */

	    *dst++ = '\n';
	    dstLen--;
	    sawLF++;
	}
	sawLF += TranslateOutputEOL(chanPtr, dst, src, &dstLen, &toWrite);
	sawLF += TranslateOutputEOL(statePtr, dst, src, &dstLen, &toWrite);
	dstLen += savedLF;
	savedLF = 0;

	if (dstLen > dstMax) {
	    savedLF = 1;
	    dstLen = dstMax;
	}

static int
WriteChars(chanPtr, src, srcLen)
    Channel *chanPtr;		/* The channel to buffer output for. */
    CONST char *src;		/* UTF-8 string to write. */
    int srcLen;			/* Length of UTF-8 string in bytes. */
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    char *dst, *stage;
    int saved, savedLF, sawLF, total, toWrite, flags;
    int dstWrote, dstLen, stageLen, stageMax, stageRead;
    Tcl_Encoding encoding;
    char safe[BUFFER_PADDING];
    
    total = 0;
    sawLF = 0;
    savedLF = 0;
    saved = 0;
    encoding = chanPtr->encoding;
    encoding = statePtr->encoding;

    /*
     * Loop over all UTF-8 characters in src, storing them in staging buffer
     * with proper EOL translation.
     */

    while (srcLen + savedLF > 0) {
	stage = chanPtr->outputStage;
	stageMax = chanPtr->bufSize;
	stage = statePtr->outputStage;
	stageMax = statePtr->bufSize;
	stageLen = stageMax;

	toWrite = stageLen;
	if (toWrite > srcLen) {
	    toWrite = srcLen;
	}

	if (savedLF) {
	    /*
	     * A '\n' was left over from last call to TranslateOutputEOL()
	     * and we need to store it in the staging buffer.  If the
	     * channel is line-based, we will need to flush the output
	     * buffer (after translating the staging buffer).
	     */
	    
	    *stage++ = '\n';
	    stageLen--;
	    sawLF++;
	}
	sawLF += TranslateOutputEOL(chanPtr, stage, src, &stageLen, &toWrite);
	sawLF += TranslateOutputEOL(statePtr, stage, src, &stageLen, &toWrite);

	stage -= savedLF;
	stageLen += savedLF;
	savedLF = 0;

	if (stageLen > stageMax) {
	    savedLF = 1;
	    stageLen = stageMax;
	}
	src += toWrite;
	srcLen -= toWrite;

	flags = chanPtr->outputEncodingFlags;
	flags = statePtr->outputEncodingFlags;
	if (srcLen == 0) {
	    flags |= TCL_ENCODING_END;
	}

	/*
	 * Loop over all UTF-8 characters in staging buffer, converting them
	 * to external encoding, storing them in output buffer.
	 */

	while (stageLen + saved > 0) {
	    bufPtr = chanPtr->curOutPtr;
	    bufPtr = statePtr->curOutPtr;
	    if (bufPtr == NULL) {
		bufPtr = AllocChannelBuffer(chanPtr->bufSize);
		chanPtr->curOutPtr = bufPtr;
		bufPtr = AllocChannelBuffer(statePtr->bufSize);
		statePtr->curOutPtr = bufPtr;
	    }
	    dst = bufPtr->buf + bufPtr->nextAdded;
	    dstLen = bufPtr->bufLength - bufPtr->nextAdded;

	    if (saved != 0) {
		/*
		 * Here's some translated bytes left over from the last
		 * buffer that we need to stick at the beginning of this
		 * buffer.
		 */
		 
		memcpy((VOID *) dst, (VOID *) safe, (size_t) saved);
		bufPtr->nextAdded += saved;
		dst += saved;
		dstLen -= saved;
		saved = 0;
	    }

	    Tcl_UtfToExternal(NULL, encoding, stage, stageLen, flags,
		    &chanPtr->outputEncodingState, dst,
		    &statePtr->outputEncodingState, dst,
		    dstLen + BUFFER_PADDING, &stageRead, &dstWrote, NULL);
	    if (stageRead + dstWrote == 0) {
		/*
		 * We have an incomplete UTF-8 character at the end of the
		 * staging buffer.  It will get moved to the beginning of the
		 * staging buffer followed by more bytes from src.
		 */

 *	buffer), the number of bytes consumed from the source buffer
 *	will be less than the number of bytes stored in the output buffer.
 *
 *---------------------------------------------------------------------------
 */

static int
TranslateOutputEOL(chanPtr, dst, src, dstLenPtr, srcLenPtr)
    Channel *chanPtr;		/* Channel being read, for translation and
TranslateOutputEOL(statePtr, dst, src, dstLenPtr, srcLenPtr)
    ChannelState *statePtr;	/* Channel being read, for translation and
				 * buffering modes. */
    char *dst;			/* Output buffer filled with UTF-8 chars by
				 * applying appropriate EOL translation to
				 * source characters. */
    CONST char *src;		/* Source UTF-8 characters. */
    int *dstLenPtr;		/* On entry, the maximum length of output
				 * buffer in bytes.  On exit, the number of
				 * bytes actually used in output buffer. */
    int *srcLenPtr;		/* On entry, the length of source buffer.
				 * On exit, the number of bytes read from
				 * the source buffer. */
{
    char *dstEnd;
    int srcLen, newlineFound;
    
    newlineFound = 0;
    srcLen = *srcLenPtr;

    switch (chanPtr->outputTranslation) {
    switch (statePtr->outputTranslation) {
	case TCL_TRANSLATE_LF: {
	    for (dstEnd = dst + srcLen; dst < dstEnd; ) {
		if (*src == '\n') {
		    newlineFound = 1;
		}
		*dst++ = *src++;
	    }

static int
CheckFlush(chanPtr, bufPtr, newlineFlag)
    Channel *chanPtr;		/* Channel being read, for buffering mode. */
    ChannelBuffer *bufPtr;	/* Channel buffer to possibly flush. */
    int newlineFlag;		/* Non-zero if a the channel buffer
				 * contains a newline. */
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    /*
     * The current buffer is ready for output:
     * 1. if it is full.
     * 2. if it contains a newline and this channel is line-buffered.
     * 3. if it contains any output and this channel is unbuffered.
     */

    if ((chanPtr->flags & BUFFER_READY) == 0) {
    if ((statePtr->flags & BUFFER_READY) == 0) {
	if (bufPtr->nextAdded == bufPtr->bufLength) {
	    chanPtr->flags |= BUFFER_READY;
	} else if (chanPtr->flags & CHANNEL_LINEBUFFERED) {
	    statePtr->flags |= BUFFER_READY;
	} else if (statePtr->flags & CHANNEL_LINEBUFFERED) {
	    if (newlineFlag != 0) {
		chanPtr->flags |= BUFFER_READY;
		statePtr->flags |= BUFFER_READY;
	    }
	} else if (chanPtr->flags & CHANNEL_UNBUFFERED) {
	    chanPtr->flags |= BUFFER_READY;
	} else if (statePtr->flags & CHANNEL_UNBUFFERED) {
	    statePtr->flags |= BUFFER_READY;
	}
    }
    if (chanPtr->flags & BUFFER_READY) {
    if (statePtr->flags & BUFFER_READY) {
	if (FlushChannel(NULL, chanPtr, 0) != 0) {
	    return -1;
	}
    }
    return 0;
}


int
Tcl_GetsObj(chan, objPtr)
    Tcl_Channel chan;		/* Channel from which to read. */
    Tcl_Obj *objPtr;		/* The line read will be appended to this
				 * object as UTF-8 characters. */
{
    GetsState gs;
    Channel *chanPtr;
    int inEofChar, skip, copiedTotal;
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    int inEofChar, skip, copiedTotal;
    Tcl_Encoding encoding;
    char *dst, *dstEnd, *eol, *eof;
    Tcl_EncodingState oldState;
    int oldLength, oldFlags, oldRemoved;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_READABLE) != 0) {
    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	copiedTotal = -1;
	goto done;
    }

    bufPtr = chanPtr->inQueueHead;
    encoding = chanPtr->encoding;
    bufPtr = statePtr->inQueueHead;
    encoding = statePtr->encoding;

    /*
     * Preserved so we can restore the channel's state in case we don't
     * find a newline in the available input.
     */

    Tcl_GetStringFromObj(objPtr, &oldLength);
    oldFlags = chanPtr->inputEncodingFlags;
    oldState = chanPtr->inputEncodingState;
    oldFlags = statePtr->inputEncodingFlags;
    oldState = statePtr->inputEncodingState;
    oldRemoved = BUFFER_PADDING;
    if (bufPtr != NULL) {
	oldRemoved = bufPtr->nextRemoved;
    }

    /*
     * If there is no encoding, use "iso8859-1" -- Tcl_GetsObj() doesn't

    gs.totalChars	= 0;

    dst = objPtr->bytes + oldLength;
    dstEnd = dst;

    skip = 0;
    eof = NULL;
    inEofChar = chanPtr->inEofChar;
    inEofChar = statePtr->inEofChar;

    while (1) {
	if (dst >= dstEnd) {
	    if (FilterInputBytes(chanPtr, &gs) != 0) {
		goto restore;
	    }
	    dstEnd = dst + gs.bytesWrote;

	/*
	 * On EOL, leave current file position pointing after the EOL, but
	 * don't store the EOL in the output string.
	 */

	eol = dst;
	switch (chanPtr->inputTranslation) {
	switch (statePtr->inputTranslation) {
	    case TCL_TRANSLATE_LF: {
		for (eol = dst; eol < dstEnd; eol++) {
		    if (*eol == '\n') {
			skip = 1;
			goto goteol;
		    }
		}

			}
		    }
		}
		break;
	    }
	    case TCL_TRANSLATE_AUTO: {
		skip = 1;
		if (chanPtr->flags & INPUT_SAW_CR) {
		    chanPtr->flags &= ~INPUT_SAW_CR;
		if (statePtr->flags & INPUT_SAW_CR) {
		    statePtr->flags &= ~INPUT_SAW_CR;
		    if (*eol == '\n') {
			/*
			 * Skip the raw bytes that make up the '\n'.
			 */

			char tmp[1 + TCL_UTF_MAX];
			int rawRead;

			bufPtr = gs.bufPtr;
			Tcl_ExternalToUtf(NULL, gs.encoding,
				bufPtr->buf + bufPtr->nextRemoved,
				gs.rawRead, chanPtr->inputEncodingFlags,
				gs.rawRead, statePtr->inputEncodingFlags,
				&gs.state, tmp, 1 + TCL_UTF_MAX, &rawRead,
				NULL, NULL);
			bufPtr->nextRemoved += rawRead;
			gs.rawRead -= rawRead;
			gs.bytesWrote--;
			gs.charsWrote--;
			memmove(dst, dst + 1, (size_t) (dstEnd - dst));

			    
			    offset = eol - objPtr->bytes;
			    dst = dstEnd;
			    PeekAhead(chanPtr, &dstEnd, &gs);
			    eol = objPtr->bytes + offset;
			    if (eol >= dstEnd) {
				eol--;
				chanPtr->flags |= INPUT_SAW_CR;
				statePtr->flags |= INPUT_SAW_CR;
				goto goteol;
			    }
			}
			if (*eol == '\n') {
			    skip++;
			}
			eol--;

	    /*
	     * EOF character was seen.  On EOF, leave current file position
	     * pointing at the EOF character, but don't store the EOF
	     * character in the output string.
	     */

	    dstEnd = eof;
	    chanPtr->flags |= (CHANNEL_EOF | CHANNEL_STICKY_EOF);
	    chanPtr->inputEncodingFlags |= TCL_ENCODING_END;
	    statePtr->flags |= (CHANNEL_EOF | CHANNEL_STICKY_EOF);
	    statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	}
	if (chanPtr->flags & CHANNEL_EOF) {
	if (statePtr->flags & CHANNEL_EOF) {
	    skip = 0;
	    eol = dstEnd;
	    if (eol == objPtr->bytes) {
		/*
		 * If we didn't produce any bytes before encountering EOF,
		 * caller needs to see -1.
		 */

     * the number of UTF-8 characters we want, plus how many raw bytes
     * correspond to the character(s) making up EOL (if any), so we can
     * remove the correct number of bytes from the channel buffer.
     */
     
    goteol:
    bufPtr = gs.bufPtr;
    chanPtr->inputEncodingState = gs.state;
    statePtr->inputEncodingState = gs.state;
    Tcl_ExternalToUtf(NULL, gs.encoding, bufPtr->buf + bufPtr->nextRemoved,
	    gs.rawRead, chanPtr->inputEncodingFlags,
	    &chanPtr->inputEncodingState, dst, eol - dst + skip + TCL_UTF_MAX,
	    gs.rawRead, statePtr->inputEncodingFlags,
	    &statePtr->inputEncodingState, dst, eol - dst + skip + TCL_UTF_MAX,
	    &gs.rawRead, NULL, &gs.charsWrote);
    bufPtr->nextRemoved += gs.rawRead;

    /*
     * Recycle all the emptied buffers.
     */

    Tcl_SetObjLength(objPtr, eol - objPtr->bytes);
    CommonGetsCleanup(chanPtr, encoding);
    chanPtr->flags &= ~CHANNEL_BLOCKED;
    statePtr->flags &= ~CHANNEL_BLOCKED;
    copiedTotal = gs.totalChars + gs.charsWrote - skip;
    goto done;

    /*
     * Couldn't get a complete line.  This only happens if we get a error
     * reading from the channel or we are non-blocking and there wasn't
     * an EOL or EOF in the data available.
     */

    restore:
    bufPtr = chanPtr->inQueueHead;
    bufPtr = statePtr->inQueueHead;
    bufPtr->nextRemoved = oldRemoved;

    for (bufPtr = bufPtr->nextPtr; bufPtr != NULL; bufPtr = bufPtr->nextPtr) {
	bufPtr->nextRemoved = BUFFER_PADDING;
    }
    CommonGetsCleanup(chanPtr, encoding);

    chanPtr->inputEncodingState = oldState;
    chanPtr->inputEncodingFlags = oldFlags;
    statePtr->inputEncodingState = oldState;
    statePtr->inputEncodingFlags = oldFlags;
    Tcl_SetObjLength(objPtr, oldLength);

    /*
     * We didn't get a complete line so we need to indicate to UpdateInterest
     * that the gets blocked.  It will wait for more data instead of firing
     * a timer, avoiding a busy wait.  This is where we are assuming that the
     * next operation is a gets.  No more file events will be delivered on 
     * this channel until new data arrives or some operation is performed
     * on the channel (e.g. gets, read, fconfigure) that changes the blocking
     * state.  Note that this means a file event will not be delivered even
     * though a read would be able to consume the buffered data.
     */

    chanPtr->flags |= CHANNEL_NEED_MORE_DATA;
    statePtr->flags |= CHANNEL_NEED_MORE_DATA;
    copiedTotal = -1;

    done:
    /*
     * Update the notifier state so we don't block while there is still
     * data in the buffers.
     */

 */
 
static int
FilterInputBytes(chanPtr, gsPtr)
    Channel *chanPtr;		/* Channel to read. */
    GetsState *gsPtr;		/* Current state of gets operation. */
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    char *raw, *rawStart, *rawEnd;
    char *dst;
    int offset, toRead, dstNeeded, spaceLeft, result, rawLen, length;
    Tcl_Obj *objPtr;
#define ENCODING_LINESIZE   30	/* Lower bound on how many bytes to convert
				 * at a time.  Since we don't know a priori

	/*
	 * All channel buffers were exhausted and the caller still hasn't
	 * seen EOL.  Need to read more bytes from the channel device.
	 * Side effect is to allocate another channel buffer.
	 */
	 
	read:
        if (chanPtr->flags & CHANNEL_BLOCKED) {
            if (chanPtr->flags & CHANNEL_NONBLOCKING) {
        if (statePtr->flags & CHANNEL_BLOCKED) {
            if (statePtr->flags & CHANNEL_NONBLOCKING) {
		gsPtr->charsWrote = 0;
		gsPtr->rawRead = 0;
		return -1;
	    }
            chanPtr->flags &= ~CHANNEL_BLOCKED;
            statePtr->flags &= ~CHANNEL_BLOCKED;
        }
	if (GetInput(chanPtr) != 0) {
	    gsPtr->charsWrote = 0;
	    gsPtr->rawRead = 0;
	    return -1;
	}
	bufPtr = chanPtr->inQueueTail;
	bufPtr = statePtr->inQueueTail;
	gsPtr->bufPtr = bufPtr;
    }

    /*
     * Convert some of the bytes from the channel buffer to UTF-8.  Space in
     * objPtr's string rep is used to hold the UTF-8 characters.  Grow the
     * string rep if we need more space.

	}
	length += TCL_UTF_MAX + 1;
	Tcl_SetObjLength(objPtr, length);
	spaceLeft = length - offset;
	dst = objPtr->bytes + offset;
	*gsPtr->dstPtr = dst;
    }
    gsPtr->state = chanPtr->inputEncodingState;
    gsPtr->state = statePtr->inputEncodingState;
    result = Tcl_ExternalToUtf(NULL, gsPtr->encoding, raw, rawLen,
	    chanPtr->inputEncodingFlags, &chanPtr->inputEncodingState,
	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
	    dst, spaceLeft, &gsPtr->rawRead, &gsPtr->bytesWrote,
	    &gsPtr->charsWrote); 
    if (result == TCL_CONVERT_MULTIBYTE) {
	/*
	 * The last few bytes in this channel buffer were the start of a
	 * multibyte sequence.  If this buffer was full, then move them to
	 * the next buffer so the bytes will be contiguous.  
	 */

	ChannelBuffer *nextPtr;
	int extra;
	
	nextPtr = bufPtr->nextPtr;
	if (bufPtr->nextAdded < bufPtr->bufLength) {
	    if (gsPtr->rawRead > 0) {
		/*
		 * Some raw bytes were converted to UTF-8.  Fall through,
		 * returning those UTF-8 characters because a EOL might be
		 * present in them.
		 */
	    } else if (chanPtr->flags & CHANNEL_EOF) {
	    } else if (statePtr->flags & CHANNEL_EOF) {
		/*
		 * There was a partial character followed by EOF on the
		 * device.  Fall through, returning that nothing was found.
		 */

		bufPtr->nextRemoved = bufPtr->nextAdded;
	    } else {
		/*
		 * There are no more cached raw bytes left.  See if we can
		 * get some more.
		 */

		goto read;
	    }
	} else {
	    if (nextPtr == NULL) {
		nextPtr = AllocChannelBuffer(chanPtr->bufSize);
		nextPtr = AllocChannelBuffer(statePtr->bufSize);
		bufPtr->nextPtr = nextPtr;
		chanPtr->inQueueTail = nextPtr;
		statePtr->inQueueTail = nextPtr;
	    }
	    extra = rawLen - gsPtr->rawRead;
	    memcpy((VOID *) (nextPtr->buf + BUFFER_PADDING - extra),
		    (VOID *) (raw + gsPtr->rawRead), (size_t) extra);
	    nextPtr->nextRemoved -= extra;
	    bufPtr->nextAdded -= extra;
	}

static void
PeekAhead(chanPtr, dstEndPtr, gsPtr)
    Channel *chanPtr;		/* The channel to read. */
    char **dstEndPtr;		/* Filled with pointer to end of new range
				 * of UTF-8 characters. */
    GetsState *gsPtr;		/* Current state of gets operation. */
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    Tcl_DriverBlockModeProc *blockModeProc;
    int bytesLeft;

    bufPtr = gsPtr->bufPtr;

    /*

	    if (bufPtr->nextAdded < bufPtr->bufLength) {
		/*
		 * Don't peek ahead if last read was short read.
		 */
		 
		goto cleanup;
	    }
	    if ((chanPtr->flags & CHANNEL_NONBLOCKING) == 0) {
		blockModeProc = chanPtr->typePtr->blockModeProc;
	    if ((statePtr->flags & CHANNEL_NONBLOCKING) == 0) {
		blockModeProc = Tcl_ChannelBlockModeProc(chanPtr->typePtr);
		if (blockModeProc == NULL) {
		    /*
		     * Don't peek ahead if cannot set non-blocking mode.
		     */

		    goto cleanup;
		}
		(*blockModeProc)(chanPtr->instanceData, TCL_MODE_NONBLOCKING);
		StackSetBlockMode(chanPtr, TCL_MODE_NONBLOCKING);
	    }
	}
    }
    if (FilterInputBytes(chanPtr, gsPtr) == 0) {
	*dstEndPtr = *gsPtr->dstPtr + gsPtr->bytesWrote;
    }
    if (blockModeProc != NULL) {
	(*blockModeProc)(chanPtr->instanceData, TCL_MODE_BLOCKING);
	StackSetBlockMode(chanPtr, TCL_MODE_BLOCKING);
    }
    return;

    cleanup:
    bufPtr->nextRemoved += gsPtr->rawRead;
    gsPtr->rawRead = 0;
    gsPtr->totalChars += gsPtr->charsWrote;

 */
 
static void
CommonGetsCleanup(chanPtr, encoding)
    Channel *chanPtr;
    Tcl_Encoding encoding;
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr, *nextPtr;
    
    bufPtr = chanPtr->inQueueHead;
    bufPtr = statePtr->inQueueHead;
    for ( ; bufPtr != NULL; bufPtr = nextPtr) {
	nextPtr = bufPtr->nextPtr;
	if (bufPtr->nextRemoved < bufPtr->nextAdded) {
	    break;
	}
	RecycleBuffer(chanPtr, bufPtr, 0);
	RecycleBuffer(statePtr, bufPtr, 0);
    }
    chanPtr->inQueueHead = bufPtr;
    statePtr->inQueueHead = bufPtr;
    if (bufPtr == NULL) {
	chanPtr->inQueueTail = NULL;
	statePtr->inQueueTail = NULL;
    } else {
	/*
	 * If any multi-byte characters were split across channel buffer
	 * boundaries, the split-up bytes were moved to the next channel
	 * buffer by FilterInputBytes().  Move the bytes back to their
	 * original buffer because the caller could change the channel's
	 * encoding which could change the interpretation of whether those

			(size_t) extra);
		bufPtr->nextAdded += extra;
		nextPtr->nextRemoved = BUFFER_PADDING;
	    }
	    bufPtr = nextPtr;
	}
    }
    if (chanPtr->encoding == NULL) {
    if (statePtr->encoding == NULL) {
	Tcl_FreeEncoding(encoding);
    }
}

/*
 *----------------------------------------------------------------------
 *

int
Tcl_Read(chan, dst, bytesToRead)
    Tcl_Channel chan;		/* The channel from which to read. */
    char *dst;			/* Where to store input read. */
    int bytesToRead;		/* Maximum number of bytes to read. */
{
    Channel *chanPtr;		
    
    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_READABLE) != 0) {
    Channel *chanPtr = (Channel *) chan;		
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	return -1;
    }

    return DoRead(chanPtr, dst, bytesToRead);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_ReadRaw --
 *
 *	Reads a given number of bytes from a channel.  EOL and EOF
 *	translation is done on the bytes being read, so the the number
 *	of bytes consumed from the channel may not be equal to the
 *	number of bytes stored in the destination buffer.
 *
 *	No encoding conversions are applied to the bytes being read.
 *
 * Results:
 *	The number of bytes read, or -1 on error. Use Tcl_GetErrno()
 *	to retrieve the error code for the error that occurred.
 *
 * Side effects:
 *	May cause input to be buffered.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ReadRaw(chan, bufPtr, bytesToRead)
    Tcl_Channel chan;		/* The channel from which to read. */
    char *bufPtr;			/* Where to store input read. */
    int bytesToRead;		/* Maximum number of bytes to read. */
{
    Channel *chanPtr = (Channel *) chan;		
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    int nread, result;
    int copied, copiedNow;

    /*
     * The check below does too much because it will reject a call to this
     * function with a channel which is part of an 'fcopy'. But we have to
     * allow this here or else the chaining in the transformation drivers
     * will fail with 'file busy' error instead of retrieving and
     * transforming the data to copy.
     *
     * We let the check procedure now believe that there is no fcopy in
     * progress. A better solution than this might be an additional flag
     * argument to switch off specific checks.
     */

    if (CheckChannelErrors(statePtr, TCL_READABLE | CHANNEL_RAW_MODE) != 0) {
	return -1;
    }

    /*
     * Check for information in the push-back buffers. If there is
     * some, use it. Go to the driver only if there is none (anymore)
     * and the caller requests more bytes.
     */

    for (copied = 0; copied < bytesToRead; copied += copiedNow) {
        copiedNow = CopyBuffer(chanPtr, bufPtr + copied,
                bytesToRead - copied);
        if (copiedNow == 0) {
            if (statePtr->flags & CHANNEL_EOF) {
		goto done;
            }
            if (statePtr->flags & CHANNEL_BLOCKED) {
                if (statePtr->flags & CHANNEL_NONBLOCKING) {
		    goto done;
                }
                statePtr->flags &= (~(CHANNEL_BLOCKED));
            }

	    /*
	     * Now go to the driver to get as much as is possible to
	     * fill the remaining request. Do all the error handling
	     * by ourselves.  The code was stolen from 'GetInput' and
	     * slightly adapted (different return value here).
	     *
	     * The case of 'bytesToRead == 0' at this point cannot happen.
	     */

	    nread = (chanPtr->typePtr->inputProc)(chanPtr->instanceData,
			  bufPtr + copied, bytesToRead - copied, &result);
	    if (nread > 0) {
	        /*
		 * If we get a short read, signal up that we may be
		 * BLOCKED. We should avoid calling the driver because
		 * on some platforms we will block in the low level
		 * reading code even though the channel is set into
		 * nonblocking mode.
		 */
            
	        if (nread < (bytesToRead - copied)) {
		    statePtr->flags |= CHANNEL_BLOCKED;
		}
	    } else if (nread == 0) {
	        statePtr->flags |= CHANNEL_EOF;
		statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	    } else if (nread < 0) {
	        if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
		    if (copied > 0) {
		      /*
		       * Information that was copied earlier has precedence
		       * over EAGAIN/WOULDBLOCK handling.
		       */
		      return copied;
		    }

		    statePtr->flags |= CHANNEL_BLOCKED;
		    result = EAGAIN;
		}

		Tcl_SetErrno(result);
		return -1;
	    } 

	    return copied + nread;
        }
    }

done:
    return copied;
}

/*
 *---------------------------------------------------------------------------
 *
 * Tcl_ReadChars --
 *
 *	Reads from the channel until the requested number of characters

				 * or when channel blocks). */
    int appendFlag;		/* If non-zero, data read from the channel
				 * will be appended to the object.  Otherwise,
				 * the data will replace the existing contents
				 * of the object. */

{
    Channel *chanPtr;
    int offset, factor, copied, copiedNow, result;
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    int offset, factor, copied, copiedNow, result;
    Tcl_Encoding encoding;
#define UTF_EXPANSION_FACTOR	1024
    
    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_READABLE) != 0) {
    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	copied = -1;
	goto done;
    }

    encoding = chanPtr->encoding;
    encoding = statePtr->encoding;
    factor = UTF_EXPANSION_FACTOR;

    if (appendFlag == 0) {
	if (encoding == NULL) {
	    Tcl_SetByteArrayLength(objPtr, 0);
	} else {
	    Tcl_SetObjLength(objPtr, 0);
	}
	offset = 0;
    } else {
	if (encoding == NULL) {
	    Tcl_GetByteArrayFromObj(objPtr, &offset);
	} else {
	    Tcl_GetStringFromObj(objPtr, &offset);
	}
    }

    for (copied = 0; (unsigned) toRead > 0; ) {
	copiedNow = -1;
	if (chanPtr->inQueueHead != NULL) {
	if (statePtr->inQueueHead != NULL) {
	    if (encoding == NULL) {
		copiedNow = ReadBytes(chanPtr, objPtr, toRead, &offset);
		copiedNow = ReadBytes(statePtr, objPtr, toRead, &offset);
	    } else {
		copiedNow = ReadChars(chanPtr, objPtr, toRead, &offset,
		copiedNow = ReadChars(statePtr, objPtr, toRead, &offset,
			&factor);
	    }

	    /*
	     * If the current buffer is empty recycle it.
	     */

	    bufPtr = chanPtr->inQueueHead;
	    bufPtr = statePtr->inQueueHead;
	    if (bufPtr->nextRemoved == bufPtr->nextAdded) {
		ChannelBuffer *nextPtr;

		nextPtr = bufPtr->nextPtr;
		RecycleBuffer(chanPtr, bufPtr, 0);
		chanPtr->inQueueHead = nextPtr;
		RecycleBuffer(statePtr, bufPtr, 0);
		statePtr->inQueueHead = nextPtr;
		if (nextPtr == NULL) {
		    chanPtr->inQueueTail = nextPtr;
		    statePtr->inQueueTail = nextPtr;
		}
	    }
	}
	if (copiedNow < 0) {
	    if (chanPtr->flags & CHANNEL_EOF) {
	    if (statePtr->flags & CHANNEL_EOF) {
		break;
	    }
	    if (chanPtr->flags & CHANNEL_BLOCKED) {
		if (chanPtr->flags & CHANNEL_NONBLOCKING) {
	    if (statePtr->flags & CHANNEL_BLOCKED) {
		if (statePtr->flags & CHANNEL_NONBLOCKING) {
		    break;
		}
		chanPtr->flags &= ~CHANNEL_BLOCKED;
		statePtr->flags &= ~CHANNEL_BLOCKED;
	    }
	    result = GetInput(chanPtr);
	    if (result != 0) {
		if (result == EAGAIN) {
		    break;
		}
		copied = -1;
		goto done;
	    }
	} else {
	    copied += copiedNow;
	    toRead -= copiedNow;
	}
    }
    chanPtr->flags &= ~CHANNEL_BLOCKED;
    statePtr->flags &= ~CHANNEL_BLOCKED;
    if (encoding == NULL) {
	Tcl_SetByteArrayLength(objPtr, offset);
    } else {
	Tcl_SetObjLength(objPtr, offset);
    }

    done:

 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
ReadBytes(chanPtr, objPtr, bytesToRead, offsetPtr)
    Channel *chanPtr;		/* The channel to read. */
ReadBytes(statePtr, objPtr, bytesToRead, offsetPtr)
    ChannelState *statePtr;	/* State of the channel to read. */
    int bytesToRead;		/* Maximum number of characters to store,
				 * or < 0 to get all available characters.
				 * Characters are obtained from the first
				 * buffer in the queue -- even if this number
				 * is larger than the number of characters
				 * available in the first buffer, only the
				 * characters from the first buffer are

{
    int toRead, srcLen, srcRead, dstWrote, offset, length;
    ChannelBuffer *bufPtr;
    char *src, *dst;

    offset = *offsetPtr;

    bufPtr = chanPtr->inQueueHead; 
    bufPtr = statePtr->inQueueHead; 
    src = bufPtr->buf + bufPtr->nextRemoved;
    srcLen = bufPtr->nextAdded - bufPtr->nextRemoved;

    toRead = bytesToRead;
    if ((unsigned) toRead > (unsigned) srcLen) {
	toRead = srcLen;
    }

	if (offset < toRead) {
	    length = offset + toRead + 1;
	}
	dst = (char *) Tcl_SetByteArrayLength(objPtr, length);
    }
    dst += offset;

    if (chanPtr->flags & INPUT_NEED_NL) {
	chanPtr->flags &= ~INPUT_NEED_NL;
    if (statePtr->flags & INPUT_NEED_NL) {
	statePtr->flags &= ~INPUT_NEED_NL;
	if ((srcLen == 0) || (*src != '\n')) {
	    *dst = '\r';
	    *offsetPtr += 1;
	    return 1;
	}
	*dst++ = '\n';
	src++;
	srcLen--;
	toRead--;
    }

    srcRead = srcLen;
    dstWrote = toRead;
    if (TranslateInputEOL(chanPtr, dst, src, &dstWrote, &srcRead) != 0) {
    if (TranslateInputEOL(statePtr, dst, src, &dstWrote, &srcRead) != 0) {
	if (dstWrote == 0) {
	    return -1;
	}
    }
    bufPtr->nextRemoved += srcRead;
    *offsetPtr += dstWrote;
    return dstWrote;

 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
ReadChars(chanPtr, objPtr, charsToRead, offsetPtr, factorPtr)
    Channel *chanPtr;		/* The channel to read. */
ReadChars(statePtr, objPtr, charsToRead, offsetPtr, factorPtr)
    ChannelState *statePtr;	/* State of channel to read. */
    int charsToRead;		/* Maximum number of characters to store,
				 * or -1 to get all available characters.
				 * Characters are obtained from the first
				 * buffer in the queue -- even if this number
				 * is larger than the number of characters
				 * available in the first buffer, only the
				 * characters from the first buffer are

    ChannelBuffer *bufPtr;
    char *src, *dst;
    Tcl_EncodingState oldState;

    factor = *factorPtr;
    offset = *offsetPtr;

    bufPtr = chanPtr->inQueueHead; 
    bufPtr = statePtr->inQueueHead; 
    src = bufPtr->buf + bufPtr->nextRemoved;
    srcLen = bufPtr->nextAdded - bufPtr->nextRemoved;

    toRead = charsToRead;
    if ((unsigned) toRead > (unsigned) srcLen) {
	toRead = srcLen;
    }

	 * rather than using the factor.
	 */

	dstNeeded = spaceLeft;
    }
    dst = objPtr->bytes + offset;

    oldState = chanPtr->inputEncodingState;
    if (chanPtr->flags & INPUT_NEED_NL) {
    oldState = statePtr->inputEncodingState;
    if (statePtr->flags & INPUT_NEED_NL) {
	/*
	 * We want a '\n' because the last character we saw was '\r'.
	 */
	 
	chanPtr->flags &= ~INPUT_NEED_NL;
	Tcl_ExternalToUtf(NULL, chanPtr->encoding, src, srcLen,
		chanPtr->inputEncodingFlags, &chanPtr->inputEncodingState,

	statePtr->flags &= ~INPUT_NEED_NL;
	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
		dst, TCL_UTF_MAX + 1, &srcRead, &dstWrote, &numChars);
	if ((dstWrote > 0) && (*dst == '\n')) {
	    /*
	     * The next char was a '\n'.  Consume it and produce a '\n'.
	     */
	     

	    bufPtr->nextRemoved += srcRead;
	} else {
	    /*
	     * The next char was not a '\n'.  Produce a '\r'.
	     */

	    *dst = '\r';
	}
	chanPtr->inputEncodingFlags &= ~TCL_ENCODING_START;
	statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;
	*offsetPtr += 1;
        return 1;
    }

    Tcl_ExternalToUtf(NULL, chanPtr->encoding, src, srcLen,
	    chanPtr->inputEncodingFlags, &chanPtr->inputEncodingState, dst,
    Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
	    statePtr->inputEncodingFlags, &statePtr->inputEncodingState, dst,
	    dstNeeded + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
    if (srcRead == 0) {
	/*
	 * Not enough bytes in src buffer to make a complete char.  Copy
	 * the bytes to the next buffer to make a new contiguous string,
	 * then tell the caller to fill the buffer with more bytes.
	 */

	ChannelBuffer *nextPtr;
	
	nextPtr = bufPtr->nextPtr;
	if (nextPtr == NULL) {
	    /*
	     * There isn't enough data in the buffers to complete the next
	     * character, so we need to wait for more data before the next
	     * file event can be delivered.
	     */

	    chanPtr->flags |= CHANNEL_NEED_MORE_DATA;
	    statePtr->flags |= CHANNEL_NEED_MORE_DATA;
	    return -1;
	}
	nextPtr->nextRemoved -= srcLen;
	memcpy((VOID *) (nextPtr->buf + nextPtr->nextRemoved), (VOID *) src,
		(size_t) srcLen);
	RecycleBuffer(chanPtr, bufPtr, 0);
	chanPtr->inQueueHead = nextPtr;
	return ReadChars(chanPtr, objPtr, charsToRead, offsetPtr, factorPtr);
	RecycleBuffer(statePtr, bufPtr, 0);
	statePtr->inQueueHead = nextPtr;
	return ReadChars(statePtr, objPtr, charsToRead, offsetPtr, factorPtr);
    }

    dstRead = dstWrote;
    if (TranslateInputEOL(chanPtr, dst, dst, &dstWrote, &dstRead) != 0) {
    if (TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead) != 0) {
	/*
	 * Hit EOF char.  How many bytes of src correspond to where the
	 * EOF was located in dst?
	 */
	 
	if (dstWrote == 0) {
	    return -1;
	}
	chanPtr->inputEncodingState = oldState;
	Tcl_ExternalToUtf(NULL, chanPtr->encoding, src, srcLen,
		chanPtr->inputEncodingFlags, &chanPtr->inputEncodingState,
	statePtr->inputEncodingState = oldState;
	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
		dst, dstRead + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
	TranslateInputEOL(chanPtr, dst, dst, &dstWrote, &dstRead);
	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
    } 

    /*
     * The number of characters that we got may be less than the number
     * that we started with because "\r\n" sequences may have been
     * turned into just '\n' in dst.
     */

    numChars -= (dstRead - dstWrote);

    if ((unsigned) numChars > (unsigned) toRead) {
	/*
	 * Got too many chars.
	 */

	char *eof;

	eof = Tcl_UtfAtIndex(dst, toRead);
	chanPtr->inputEncodingState = oldState;
	Tcl_ExternalToUtf(NULL, chanPtr->encoding, src, srcLen,
		chanPtr->inputEncodingFlags, &chanPtr->inputEncodingState,
	statePtr->inputEncodingState = oldState;
	Tcl_ExternalToUtf(NULL, statePtr->encoding, src, srcLen,
		statePtr->inputEncodingFlags, &statePtr->inputEncodingState,
		dst, eof - dst + TCL_UTF_MAX, &srcRead, &dstWrote, &numChars);
	dstRead = dstWrote;
	TranslateInputEOL(chanPtr, dst, dst, &dstWrote, &dstRead);
	TranslateInputEOL(statePtr, dst, dst, &dstWrote, &dstRead);
	numChars -= (dstRead - dstWrote);
    }
    chanPtr->inputEncodingFlags &= ~TCL_ENCODING_START;
    statePtr->inputEncodingFlags &= ~TCL_ENCODING_START;

    bufPtr->nextRemoved += srcRead;
    if (dstWrote > srcRead + 1) {
	*factorPtr = dstWrote * UTF_EXPANSION_FACTOR / srcRead;
    }
    *offsetPtr += dstWrote;
    return numChars;

 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
TranslateInputEOL(chanPtr, dstStart, srcStart, dstLenPtr, srcLenPtr)
    Channel *chanPtr;		/* Channel being read, for EOL translation
TranslateInputEOL(statePtr, dstStart, srcStart, dstLenPtr, srcLenPtr)
    ChannelState *statePtr;	/* Channel being read, for EOL translation
				 * and EOF character. */
    char *dstStart;		/* Output buffer filled with chars by
				 * applying appropriate EOL translation to
				 * source characters. */
    CONST char *srcStart;	/* Source characters. */
    int *dstLenPtr;		/* On entry, the maximum length of output
				 * buffer in bytes; must be <= *srcLenPtr.  On
				 * exit, the number of bytes actually used in
				 * output buffer. */
    int *srcLenPtr;		/* On entry, the length of source buffer.
				 * On exit, the number of bytes read from
				 * the source buffer. */
{
    int dstLen, srcLen, inEofChar;
    CONST char *eof;

    dstLen = *dstLenPtr;

    eof = NULL;
    inEofChar = chanPtr->inEofChar;
    inEofChar = statePtr->inEofChar;
    if (inEofChar != '\0') {
	/*
	 * Find EOF in translated buffer then compress out the EOL.  The
	 * source buffer may be much longer than the destination buffer --
	 * we only want to return EOF if the EOF has been copied to the
	 * destination buffer.
	 */

		    dstLen = srcLen;
		}
		*srcLenPtr = srcLen;
		break;
	    }
	}
    }
    switch (chanPtr->inputTranslation) {
    switch (statePtr->inputTranslation) {
	case TCL_TRANSLATE_LF: {
	    if (dstStart != srcStart) {
		memcpy((VOID *) dstStart, (VOID *) srcStart, (size_t) dstLen);
	    }
	    srcLen = dstLen;
	    break;
	}

	    srcEnd = srcStart + dstLen;
	    srcMax = srcStart + *srcLenPtr;

	    for ( ; src < srcEnd; ) {
		if (*src == '\r') {
		    src++;
		    if (src >= srcMax) {
			chanPtr->flags |= INPUT_NEED_NL;
			statePtr->flags |= INPUT_NEED_NL;
		    } else if (*src == '\n') {
			*dst++ = *src++;
		    } else {
			*dst++ = '\r';
		    }
		} else {
		    *dst++ = *src++;

	    CONST char *src, *srcEnd, *srcMax;

	    dst = dstStart;
	    src = srcStart;
	    srcEnd = srcStart + dstLen;
	    srcMax = srcStart + *srcLenPtr;

	    if ((chanPtr->flags & INPUT_SAW_CR) && (src < srcMax)) {
	    if ((statePtr->flags & INPUT_SAW_CR) && (src < srcMax)) {
		if (*src == '\n') {
		    src++;
		}
		chanPtr->flags &= ~INPUT_SAW_CR;
		statePtr->flags &= ~INPUT_SAW_CR;
	    }
	    for ( ; src < srcEnd; ) {
		if (*src == '\r') {
		    src++;
		    if (src >= srcMax) {
			chanPtr->flags |= INPUT_SAW_CR;
			statePtr->flags |= INPUT_SAW_CR;
		    } else if (*src == '\n') {
			if (srcEnd < srcMax) {
			    srcEnd++;
			}
			src++;
		    }
		    *dst++ = '\n';

    if ((eof != NULL) && (srcStart + srcLen >= eof)) {
	/*
	 * EOF character was seen in EOL translated range.  Leave current
	 * file position pointing at the EOF character, but don't store the
	 * EOF character in the output string.
	 */

	chanPtr->flags |= (CHANNEL_EOF | CHANNEL_STICKY_EOF);
	chanPtr->inputEncodingFlags |= TCL_ENCODING_END;
	chanPtr->flags &= ~(INPUT_SAW_CR | INPUT_NEED_NL);
	statePtr->flags |= (CHANNEL_EOF | CHANNEL_STICKY_EOF);
	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
	statePtr->flags &= ~(INPUT_SAW_CR | INPUT_NEED_NL);
	return 1;
    }

    *srcLenPtr = srcLen;
    return 0;
}


    Tcl_Channel chan;		/* The channel for which to add the input. */
    char *str;			/* The input itself. */
    int len;			/* The length of the input. */
    int atEnd;			/* If non-zero, add at end of queue; otherwise
                                 * add at head of queue. */    
{
    Channel *chanPtr;		/* The real IO channel. */
    ChannelState *statePtr;	/* State of actual channel. */
    ChannelBuffer *bufPtr;	/* Buffer to contain the data. */
    int i, flags;

    chanPtr = (Channel *) chan;
    statePtr = chanPtr->state;
    

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * CheckChannelErrors clears too many flag bits in this one case.
     */
     
    flags = chanPtr->flags;
    if (CheckChannelErrors(chanPtr, TCL_READABLE) != 0) {
    flags = statePtr->flags;
    if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
	len = -1;
	goto done;
    }
    chanPtr->flags = flags;
    statePtr->flags = flags;

    /*
     * If we have encountered a sticky EOF, just punt without storing.
     * (sticky EOF is set if we have seen the input eofChar, to prevent
     * reading beyond the eofChar). Otherwise, clear the EOF flags, and
     * clear the BLOCKED bit. We want to discover these conditions anew
     * in each operation.
     */

    if (chanPtr->flags & CHANNEL_STICKY_EOF) {
    if (statePtr->flags & CHANNEL_STICKY_EOF) {
	goto done;
    }
    chanPtr->flags &= (~(CHANNEL_BLOCKED | CHANNEL_EOF));
    statePtr->flags &= (~(CHANNEL_BLOCKED | CHANNEL_EOF));

    bufPtr = AllocChannelBuffer(len);
    for (i = 0; i < len; i++) {
        bufPtr->buf[i] = str[i];
    }
    bufPtr->nextAdded += len;

    if (chanPtr->inQueueHead == (ChannelBuffer *) NULL) {
    if (statePtr->inQueueHead == (ChannelBuffer *) NULL) {
        bufPtr->nextPtr = (ChannelBuffer *) NULL;
        chanPtr->inQueueHead = bufPtr;
        chanPtr->inQueueTail = bufPtr;
        statePtr->inQueueHead = bufPtr;
        statePtr->inQueueTail = bufPtr;
    } else if (atEnd) {
        bufPtr->nextPtr = (ChannelBuffer *) NULL;
        chanPtr->inQueueTail->nextPtr = bufPtr;
        chanPtr->inQueueTail = bufPtr;
        statePtr->inQueueTail->nextPtr = bufPtr;
        statePtr->inQueueTail = bufPtr;
    } else {
        bufPtr->nextPtr = chanPtr->inQueueHead;
        chanPtr->inQueueHead = bufPtr;
        bufPtr->nextPtr = statePtr->inQueueHead;
        statePtr->inQueueHead = bufPtr;
    }

    done:
    /*
     * Update the notifier state so we don't block while there is still
     * data in the buffers.
     */

 */

int
Tcl_Flush(chan)
    Tcl_Channel chan;			/* The Channel to flush. */
{
    int result;				/* Of calling FlushChannel. */
    Channel *chanPtr;			/* The actual channel. */
    Channel *chanPtr  = (Channel *) chan;	/* The actual channel. */
    ChannelState *statePtr = chanPtr->state;	/* State of actual channel. */

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_WRITABLE) != 0) {
    chanPtr = statePtr->topChanPtr;

    if (CheckChannelErrors(statePtr, TCL_WRITABLE) != 0) {
	return -1;
    }

    /*
     * Force current output buffer to be output also.
     */
    
    if ((chanPtr->curOutPtr != NULL)
	    && (chanPtr->curOutPtr->nextAdded > 0)) {
        chanPtr->flags |= BUFFER_READY;

    if ((statePtr->curOutPtr != NULL)
	    && (statePtr->curOutPtr->nextAdded > 0)) {
        statePtr->flags |= BUFFER_READY;
    }
    
    result = FlushChannel(NULL, chanPtr, 0);
    if (result != 0) {
        return TCL_ERROR;
    }

 *	May discard input from the channel. If discardLastBuffer is zero,
 *	leaves one buffer in place for back-filling.
 *
 *----------------------------------------------------------------------
 */

static void
DiscardInputQueued(chanPtr, discardSavedBuffers)
    Channel *chanPtr;		/* Channel on which to discard
DiscardInputQueued(statePtr, discardSavedBuffers)
    ChannelState *statePtr;	/* Channel on which to discard
                                 * the queued input. */
    int discardSavedBuffers;	/* If non-zero, discard all buffers including
                                 * last one. */
{
    ChannelBuffer *bufPtr, *nxtPtr;	/* Loop variables. */

    bufPtr = chanPtr->inQueueHead;
    chanPtr->inQueueHead = (ChannelBuffer *) NULL;
    chanPtr->inQueueTail = (ChannelBuffer *) NULL;
    bufPtr = statePtr->inQueueHead;
    statePtr->inQueueHead = (ChannelBuffer *) NULL;
    statePtr->inQueueTail = (ChannelBuffer *) NULL;
    for (; bufPtr != (ChannelBuffer *) NULL; bufPtr = nxtPtr) {
        nxtPtr = bufPtr->nextPtr;
        RecycleBuffer(chanPtr, bufPtr, discardSavedBuffers);
        RecycleBuffer(statePtr, bufPtr, discardSavedBuffers);
    }

    /*
     * If discardSavedBuffers is nonzero, must also discard any previously
     * saved buffer in the saveInBufPtr field.
     */
    
    if (discardSavedBuffers) {
        if (chanPtr->saveInBufPtr != (ChannelBuffer *) NULL) {
            ckfree((char *) chanPtr->saveInBufPtr);
            chanPtr->saveInBufPtr = (ChannelBuffer *) NULL;
        if (statePtr->saveInBufPtr != (ChannelBuffer *) NULL) {
            ckfree((char *) statePtr->saveInBufPtr);
            statePtr->saveInBufPtr = (ChannelBuffer *) NULL;
        }
    }
}

/*
 *---------------------------------------------------------------------------
 *

GetInput(chanPtr)
    Channel *chanPtr;		/* Channel to read input from. */
{
    int toRead;			/* How much to read? */
    int result;			/* Of calling driver. */
    int nread;			/* How much was read from channel? */
    ChannelBuffer *bufPtr;	/* New buffer to add to input queue. */
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */

    /*
     * Prevent reading from a dead channel -- a channel that has been closed
     * but not yet deallocated, which can happen if the exit handler for
     * channel cleanup has run but the channel is still registered in some
     * interpreter.
     */
    
    if (CheckForDeadChannel(NULL, chanPtr)) {
    if (CheckForDeadChannel(NULL, statePtr)) {
	return EINVAL;
    }

    /*
     * First check for more buffers in the pushback area of the
     * topmost channel in the stack and use them. They can be the
     * result of a transformation which went away without reading all
     * the information placed in the area when it was stacked.
     *
     * Two possibilities for the state: No buffers in it, or a single
     * empty buffer. In the latter case we can recycle it now.
     */

    if (chanPtr->inQueueHead != (ChannelBuffer*) NULL) {
        if (statePtr->inQueueHead != (ChannelBuffer*) NULL) {
	    RecycleBuffer(statePtr, statePtr->inQueueHead, 0);
	    statePtr->inQueueHead = (ChannelBuffer*) NULL;
	}

	statePtr->inQueueHead = chanPtr->inQueueHead;
	statePtr->inQueueTail = chanPtr->inQueueTail;
	chanPtr->inQueueHead  = (ChannelBuffer*) NULL;
	chanPtr->inQueueTail  = (ChannelBuffer*) NULL;
	return 0;
    }

    /*
     * Nothing in the pushback area, fall back to the usual handling
     * (driver, etc.)
     */

    /*
     * See if we can fill an existing buffer. If we can, read only
     * as much as will fit in it. Otherwise allocate a new buffer,
     * add it to the input queue and attempt to fill it to the max.
     */

    bufPtr = chanPtr->inQueueTail;
    bufPtr = statePtr->inQueueTail;
    if ((bufPtr != NULL) && (bufPtr->nextAdded < bufPtr->bufLength)) {
        toRead = bufPtr->bufLength - bufPtr->nextAdded;
    } else {
	bufPtr = chanPtr->saveInBufPtr;
	chanPtr->saveInBufPtr = NULL;
	bufPtr = statePtr->saveInBufPtr;
	statePtr->saveInBufPtr = NULL;
	if (bufPtr == NULL) {
	    bufPtr = AllocChannelBuffer(chanPtr->bufSize);
	    bufPtr = AllocChannelBuffer(statePtr->bufSize);
	}
        bufPtr->nextPtr = (ChannelBuffer *) NULL;

        toRead = chanPtr->bufSize;
        if (chanPtr->inQueueTail == NULL) {
            chanPtr->inQueueHead = bufPtr;
        toRead = statePtr->bufSize;
        if (statePtr->inQueueTail == NULL) {
            statePtr->inQueueHead = bufPtr;
        } else {
            chanPtr->inQueueTail->nextPtr = bufPtr;
            statePtr->inQueueTail->nextPtr = bufPtr;
        }
        chanPtr->inQueueTail = bufPtr;
        statePtr->inQueueTail = bufPtr;
    }
      
    /*
     * If EOF is set, we should avoid calling the driver because on some
     * platforms it is impossible to read from a device after EOF.
     */

    if (chanPtr->flags & CHANNEL_EOF) {
    if (statePtr->flags & CHANNEL_EOF) {
	return 0;
    }

    nread = (*chanPtr->typePtr->inputProc)(chanPtr->instanceData,
    nread = (chanPtr->typePtr->inputProc)(chanPtr->instanceData,
	    bufPtr->buf + bufPtr->nextAdded, toRead, &result);

    if (nread > 0) {
	bufPtr->nextAdded += nread;

	/*
	 * If we get a short read, signal up that we may be BLOCKED. We
	 * should avoid calling the driver because on some platforms we
	 * will block in the low level reading code even though the
	 * channel is set into nonblocking mode.
	 */
            
	if (nread < toRead) {
	    chanPtr->flags |= CHANNEL_BLOCKED;
	    statePtr->flags |= CHANNEL_BLOCKED;
	}
    } else if (nread == 0) {
	chanPtr->flags |= CHANNEL_EOF;
	chanPtr->inputEncodingFlags |= TCL_ENCODING_END;
	statePtr->flags |= CHANNEL_EOF;
	statePtr->inputEncodingFlags |= TCL_ENCODING_END;
    } else if (nread < 0) {
	if ((result == EWOULDBLOCK) || (result == EAGAIN)) {
	    chanPtr->flags |= CHANNEL_BLOCKED;
	    statePtr->flags |= CHANNEL_BLOCKED;
	    result = EAGAIN;
	}
	Tcl_SetErrno(result);
	return result;
    } 
    return 0;
}

int
Tcl_Seek(chan, offset, mode)
    Tcl_Channel chan;		/* The channel on which to seek. */
    int offset;			/* Offset to seek to. */
    int mode;			/* Relative to which location to seek? */
{
    Channel *chanPtr;		/* The real IO channel. */
    Channel *chanPtr = (Channel *) chan;	/* The real IO channel. */
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    int inputBuffered, outputBuffered;
    int result;			/* Of device driver operations. */
    int curPos;			/* Position on the device. */
    int wasAsync;		/* Was the channel nonblocking before the
                                 * seek operation? If so, must restore to
                                 * nonblocking mode after the seek. */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_WRITABLE | TCL_READABLE) != 0) {
    if (CheckChannelErrors(statePtr, TCL_WRITABLE | TCL_READABLE) != 0) {
	return -1;
    }

    /*
     * Disallow seek on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still
     * registered in an interpreter.
     */

    if (CheckForDeadChannel(NULL,chanPtr)) return -1;
    if (CheckForDeadChannel(NULL, statePtr)) return -1;

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * Disallow seek on channels whose type does not have a seek procedure
     * defined. This means that the channel does not support seeking.
     */

    if (chanPtr->typePtr->seekProc == (Tcl_DriverSeekProc *) NULL) {
        Tcl_SetErrno(EINVAL);
        return -1;
    }

    /*
     * Compute how much input and output is buffered. If both input and
     * output is buffered, cannot compute the current position.
     */

    for (bufPtr = chanPtr->inQueueHead, inputBuffered = 0;
    for (bufPtr = statePtr->inQueueHead, inputBuffered = 0;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        inputBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }

    /*
     * Don't forget the bytes in the topmost pushback area.
     */

    for (bufPtr = statePtr->topChanPtr->inQueueHead;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        inputBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }

    for (bufPtr = chanPtr->outQueueHead, outputBuffered = 0;
    for (bufPtr = statePtr->outQueueHead, outputBuffered = 0;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        outputBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }
    if ((chanPtr->curOutPtr != (ChannelBuffer *) NULL) &&
	    (chanPtr->curOutPtr->nextAdded > chanPtr->curOutPtr->nextRemoved)) {
        chanPtr->flags |= BUFFER_READY;
    if ((statePtr->curOutPtr != (ChannelBuffer *) NULL) &&
	    (statePtr->curOutPtr->nextAdded > statePtr->curOutPtr->nextRemoved)) {
        statePtr->flags |= BUFFER_READY;
        outputBuffered +=
            (chanPtr->curOutPtr->nextAdded - chanPtr->curOutPtr->nextRemoved);
            (statePtr->curOutPtr->nextAdded - statePtr->curOutPtr->nextRemoved);
    }

    if ((inputBuffered != 0) && (outputBuffered != 0)) {
        Tcl_SetErrno(EFAULT);
        return -1;
    }

    }

    /*
     * Discard any queued input - this input should not be read after
     * the seek.
     */

    DiscardInputQueued(chanPtr, 0);
    DiscardInputQueued(statePtr, 0);

    /*
     * Reset EOF and BLOCKED flags. We invalidate them by moving the
     * access point. Also clear CR related flags.
     */

    chanPtr->flags &=
    statePtr->flags &=
        (~(CHANNEL_EOF | CHANNEL_STICKY_EOF | CHANNEL_BLOCKED | INPUT_SAW_CR));
    
    /*
     * If the channel is in asynchronous output mode, switch it back
     * to synchronous mode and cancel any async flush that may be
     * scheduled. After the flush, the channel will be put back into
     * asynchronous output mode.
     */

    wasAsync = 0;
    if (chanPtr->flags & CHANNEL_NONBLOCKING) {
    if (statePtr->flags & CHANNEL_NONBLOCKING) {
        wasAsync = 1;
        result = 0;
        if (chanPtr->typePtr->blockModeProc != NULL) {
            result = (chanPtr->typePtr->blockModeProc) (chanPtr->instanceData,
                    TCL_MODE_BLOCKING);
        result = StackSetBlockMode(chanPtr, TCL_MODE_BLOCKING);
        }
        if (result != 0) {
	if (result != 0) {
            Tcl_SetErrno(result);
            return -1;
        }
        chanPtr->flags &= (~(CHANNEL_NONBLOCKING));
        if (chanPtr->flags & BG_FLUSH_SCHEDULED) {
            chanPtr->flags &= (~(BG_FLUSH_SCHEDULED));
	    return -1;
	}
        statePtr->flags &= (~(CHANNEL_NONBLOCKING));
        if (statePtr->flags & BG_FLUSH_SCHEDULED) {
            statePtr->flags &= (~(BG_FLUSH_SCHEDULED));
        }
    }
    
    /*
     * If the flush fails we cannot recover the original position. In
     * that case the seek is not attempted because we do not know where
     * the access position is - instead we return the error. FlushChannel

     * Restore to nonblocking mode if that was the previous behavior.
     *
     * NOTE: Even if there was an async flush active we do not restore
     * it now because we already flushed all the queued output, above.
     */
    
    if (wasAsync) {
        chanPtr->flags |= CHANNEL_NONBLOCKING;
        statePtr->flags |= CHANNEL_NONBLOCKING;
        result = 0;
        if (chanPtr->typePtr->blockModeProc != NULL) {
            result = (chanPtr->typePtr->blockModeProc) (chanPtr->instanceData,
                    TCL_MODE_NONBLOCKING);
        result = StackSetBlockMode(chanPtr, TCL_MODE_NONBLOCKING);
        }
        if (result != 0) {
	if (result != 0) {
            Tcl_SetErrno(result);
            return -1;
        }
	    return -1;
	}
    }

    return curPos;
}

/*
 *----------------------------------------------------------------------

 *----------------------------------------------------------------------
 */

int
Tcl_Tell(chan)
    Tcl_Channel chan;			/* The channel to return pos for. */
{
    Channel *chanPtr;			/* The actual channel to tell on. */
    Channel *chanPtr = (Channel *) chan;	/* The real IO channel. */
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelBuffer *bufPtr;
    int inputBuffered, outputBuffered;
    int result;				/* Of calling device driver. */
    int curPos;				/* Position on device. */

    chanPtr = (Channel *) chan;
    if (CheckChannelErrors(chanPtr, TCL_WRITABLE | TCL_READABLE) != 0) {
    if (CheckChannelErrors(statePtr, TCL_WRITABLE | TCL_READABLE) != 0) {
	return -1;
    }

    /*
     * Disallow tell on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still
     * registered in an interpreter.
     */

    if (CheckForDeadChannel(NULL,chanPtr)) {
    if (CheckForDeadChannel(NULL, statePtr)) {
	return -1;
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * Disallow tell on channels whose type does not have a seek procedure
     * defined. This means that the channel does not support seeking.
     */

    if (chanPtr->typePtr->seekProc == (Tcl_DriverSeekProc *) NULL) {
        Tcl_SetErrno(EINVAL);
        return -1;
    }

    /*
     * Compute how much input and output is buffered. If both input and
     * output is buffered, cannot compute the current position.
     */

    for (bufPtr = chanPtr->inQueueHead, inputBuffered = 0;
    for (bufPtr = statePtr->inQueueHead, inputBuffered = 0;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        inputBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }
    for (bufPtr = chanPtr->outQueueHead, outputBuffered = 0;
    for (bufPtr = statePtr->outQueueHead, outputBuffered = 0;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        outputBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }
    if ((chanPtr->curOutPtr != (ChannelBuffer *) NULL) &&
	    (chanPtr->curOutPtr->nextAdded > chanPtr->curOutPtr->nextRemoved)) {
        chanPtr->flags |= BUFFER_READY;
    if ((statePtr->curOutPtr != (ChannelBuffer *) NULL) &&
	    (statePtr->curOutPtr->nextAdded > statePtr->curOutPtr->nextRemoved)) {
        statePtr->flags |= BUFFER_READY;
        outputBuffered +=
            (chanPtr->curOutPtr->nextAdded - chanPtr->curOutPtr->nextRemoved);
            (statePtr->curOutPtr->nextAdded - statePtr->curOutPtr->nextRemoved);
    }

    if ((inputBuffered != 0) && (outputBuffered != 0)) {
        Tcl_SetErrno(EFAULT);
        return -1;
    }

 * Side effects:
 *	May clear the EOF and/or BLOCKED bits if reading from channel.
 *
 *---------------------------------------------------------------------------
 */
 
static int
CheckChannelErrors(chanPtr, direction)
    Channel *chanPtr;	    /* Channel to check. */
    int direction;	    /* Test if channel supports desired operation:
			     * TCL_READABLE, TCL_WRITABLE. */
CheckChannelErrors(statePtr, flags)
    ChannelState *statePtr;	/* Channel to check. */
    int flags;			/* Test if channel supports desired operation:
				 * TCL_READABLE, TCL_WRITABLE.  Also indicates
				 * Raw read or write for special close
				 * processing*/
{
    int direction = flags & (TCL_READABLE|TCL_WRITABLE);

    /*
     * Check for unreported error.
     */

    if (chanPtr->unreportedError != 0) {
        Tcl_SetErrno(chanPtr->unreportedError);
        chanPtr->unreportedError = 0;
    if (statePtr->unreportedError != 0) {
        Tcl_SetErrno(statePtr->unreportedError);
        statePtr->unreportedError = 0;
        return -1;
    }

    /*
     * Only the raw read and write operations are allowed during close
     * in order to drain data from stacked channels.
     */

    if ((statePtr->flags & CHANNEL_CLOSED) &&
	    ((flags & CHANNEL_RAW_MODE) == 0)) {
        Tcl_SetErrno(EACCES);
        return -1;
    }

    /*
     * Fail if the channel is not opened for desired operation.
     */

    if ((chanPtr->flags & direction) == 0) {
    if ((statePtr->flags & direction) == 0) {
        Tcl_SetErrno(EACCES);
        return -1;
    }

    /*
     * Fail if the channel is in the middle of a background copy.
     *
     * Don't do this tests for raw channels here or else the chaining in the
     * transformation drivers will fail with 'file busy' error instead of
     * retrieving and transforming the data to copy.
     */

    if (chanPtr->csPtr != NULL) {
    if ((statePtr->csPtr != NULL) && ((flags & CHANNEL_RAW_MODE) == 0)) {
	Tcl_SetErrno(EBUSY);
	return -1;
    }

    if (direction == TCL_READABLE) {
	/*
	 * If we have not encountered a sticky EOF, clear the EOF bit
	 * (sticky EOF is set if we have seen the input eofChar, to prevent
	 * reading beyond the eofChar). Also, always clear the BLOCKED bit.
	 * We want to discover these conditions anew in each operation.
	 */
	
	if ((chanPtr->flags & CHANNEL_STICKY_EOF) == 0) {
	    chanPtr->flags &= ~CHANNEL_EOF;
	if ((statePtr->flags & CHANNEL_STICKY_EOF) == 0) {
	    statePtr->flags &= ~CHANNEL_EOF;
	}
	chanPtr->flags &= ~(CHANNEL_BLOCKED | CHANNEL_NEED_MORE_DATA);
	statePtr->flags &= ~(CHANNEL_BLOCKED | CHANNEL_NEED_MORE_DATA);
    }

    return 0;
}

/*
 *----------------------------------------------------------------------

 *----------------------------------------------------------------------
 */

int
Tcl_Eof(chan)
    Tcl_Channel chan;			/* Does this channel have EOF? */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
    Channel *chanPtr;		/* The real channel structure. */
					/* State of real channel structure. */

    chanPtr = (Channel *) chan;
    return ((chanPtr->flags & CHANNEL_STICKY_EOF) ||
            ((chanPtr->flags & CHANNEL_EOF) && (Tcl_InputBuffered(chan) == 0)))
        ? 1 : 0;
    return ((statePtr->flags & CHANNEL_STICKY_EOF) ||
            ((statePtr->flags & CHANNEL_EOF) &&
		    (Tcl_InputBuffered(chan) == 0))) ? 1 : 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InputBlocked --
 *

 *----------------------------------------------------------------------
 */

int
Tcl_InputBlocked(chan)
    Tcl_Channel chan;			/* Is this channel blocked? */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
    Channel *chanPtr;		/* The real channel structure. */
					/* State of real channel structure. */

    chanPtr = (Channel *) chan;
    return (chanPtr->flags & CHANNEL_BLOCKED) ? 1 : 0;
    return (statePtr->flags & CHANNEL_BLOCKED) ? 1 : 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_InputBuffered --
 *
 *	Returns the number of bytes of input currently buffered in the
 *	internal buffer of a channel.
 *	common internal buffer of a channel.
 *
 * Results:
 *	The number of input bytes buffered, or zero if the channel is not
 *	open for reading.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_InputBuffered(chan)
    Tcl_Channel chan;			/* The channel to query. */
{
    ChannelState *statePtr = ((Channel *) chan)->state;
					/* State of real channel structure. */
    Channel *chanPtr;
    ChannelBuffer *bufPtr;
    int bytesBuffered;

    for (bytesBuffered = 0, bufPtr = statePtr->inQueueHead;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        bytesBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }

    /*
     * Don't forget the bytes in the topmost pushback area.
     */

    for (bufPtr = statePtr->topChanPtr->inQueueHead;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        bytesBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }

    return bytesBuffered;
}

/*
 *----------------------------------------------------------------------
 *
    ChannelBuffer *bufPtr;

    chanPtr = (Channel *) chan;
 * Tcl_ChannelBuffered --
 *
 *	Returns the number of bytes of input currently buffered in the
 *	internal buffer (push back area) of a channel.
 *
 * Results:
 *	The number of input bytes buffered, or zero if the channel is not
 *	open for reading.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

int
Tcl_ChannelBuffered(chan)
    Tcl_Channel chan;			/* The channel to query. */
{
    Channel *chanPtr = (Channel *) chan;
					/* State of real channel structure. */
    ChannelBuffer *bufPtr;
    int bytesBuffered;

    for (bytesBuffered = 0, bufPtr = chanPtr->inQueueHead;
	 bufPtr != (ChannelBuffer *) NULL;
	 bufPtr = bufPtr->nextPtr) {
        bytesBuffered += (bufPtr->nextAdded - bufPtr->nextRemoved);
    }

    return bytesBuffered;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetChannelBufferSize --

void
Tcl_SetChannelBufferSize(chan, sz)
    Tcl_Channel chan;			/* The channel whose buffer size
                                         * to set. */
    int sz;				/* The size to set. */
{
    Channel *chanPtr;
    ChannelState *statePtr;		/* State of real channel structure. */
    
    /*
     * If the buffer size is smaller than 10 bytes or larger than one MByte,
     * do not accept the requested size and leave the current buffer size.
     */
    
    if (sz < 10) {
        return;
    }
    if (sz > (1024 * 1024)) {
        return;
    }

    chanPtr = (Channel *) chan;
    chanPtr->bufSize = sz;
    statePtr = ((Channel *) chan)->state;
    statePtr->bufSize = sz;

    if (chanPtr->outputStage != NULL) {
	ckfree((char *) chanPtr->outputStage);
	chanPtr->outputStage = NULL;
    if (statePtr->outputStage != NULL) {
	ckfree((char *) statePtr->outputStage);
	statePtr->outputStage = NULL;
    }
    if ((chanPtr->encoding != NULL) && (chanPtr->flags & TCL_WRITABLE)) {
	chanPtr->outputStage = (char *)
	    ckalloc((unsigned) (chanPtr->bufSize + 2));
    if ((statePtr->encoding != NULL) && (statePtr->flags & TCL_WRITABLE)) {
	statePtr->outputStage = (char *)
	    ckalloc((unsigned) (statePtr->bufSize + 2));
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetChannelBufferSize --

 */

int
Tcl_GetChannelBufferSize(chan)
    Tcl_Channel chan;		/* The channel for which to find the
                                 * buffer size. */
{
    Channel *chanPtr;
    ChannelState *statePtr = ((Channel *) chan)->state;
					/* State of real channel structure. */

    chanPtr = (Channel *) chan;
    return chanPtr->bufSize;
    return statePtr->bufSize;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_BadChannelOption --
 *

    Tcl_Channel chan;		/* Channel on which to get option. */
    char *optionName;		/* Option to get. */
    Tcl_DString *dsPtr;		/* Where to store value(s). */
{
    size_t len;			/* Length of optionName string. */
    char optionVal[128];	/* Buffer for sprintf. */
    Channel *chanPtr = (Channel *) chan;
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    int flags;

    /*
     * If we are in the middle of a background copy, use the saved flags.
     */

    if (chanPtr->csPtr) {
	if (chanPtr == chanPtr->csPtr->readPtr) {
	    flags = chanPtr->csPtr->readFlags;
	} else {
	    flags = chanPtr->csPtr->writeFlags;
	}
    } else {
	flags = chanPtr->flags;
    }

    /*
     * Disallow options on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still
     * registered in an interpreter.
     */

    if (CheckForDeadChannel(interp,chanPtr)) return TCL_ERROR;
    if (CheckForDeadChannel(interp, statePtr)) {
	return TCL_ERROR;
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    /*
     * If we are in the middle of a background copy, use the saved flags.
     */

    if (statePtr->csPtr) {
	if (chanPtr == statePtr->csPtr->readPtr) {
	    flags = statePtr->csPtr->readFlags;
	} else {
	    flags = statePtr->csPtr->writeFlags;
	}
    } else {
	flags = statePtr->flags;
    }

    /*
     * If the optionName is NULL it means that we want a list of all
     * options and values.
     */
    
    if (optionName == (char *) NULL) {

        }
    }
    if ((len == 0) || ((len > 7) && (optionName[1] == 'b') &&
            (strncmp(optionName, "-buffersize", len) == 0))) {
        if (len == 0) {
            Tcl_DStringAppendElement(dsPtr, "-buffersize");
        }
        TclFormatInt(optionVal, chanPtr->bufSize);
        TclFormatInt(optionVal, statePtr->bufSize);
        Tcl_DStringAppendElement(dsPtr, optionVal);
        if (len > 0) {
            return TCL_OK;
        }
    }
    if ((len == 0) ||
	    ((len > 2) && (optionName[1] == 'e') &&
		    (strncmp(optionName, "-encoding", len) == 0))) {
	if (len == 0) {
	    Tcl_DStringAppendElement(dsPtr, "-encoding");
	}
	if (chanPtr->encoding == NULL) {
	if (statePtr->encoding == NULL) {
	    Tcl_DStringAppendElement(dsPtr, "binary");
	} else {
	    Tcl_DStringAppendElement(dsPtr,
		    Tcl_GetEncodingName(chanPtr->encoding));
		    Tcl_GetEncodingName(statePtr->encoding));
	}
	if (len > 0) {
	    return TCL_OK;
	}
    }
    if ((len == 0) ||
            ((len > 2) && (optionName[1] == 'e') &&
                    (strncmp(optionName, "-eofchar", len) == 0))) {
        if (len == 0) {
            Tcl_DStringAppendElement(dsPtr, "-eofchar");
        }
        if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
                (TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
            Tcl_DStringStartSublist(dsPtr);
        }
        if (flags & TCL_READABLE) {
            if (chanPtr->inEofChar == 0) {
            if (statePtr->inEofChar == 0) {
                Tcl_DStringAppendElement(dsPtr, "");
            } else {
                char buf[4];

                sprintf(buf, "%c", chanPtr->inEofChar);
                sprintf(buf, "%c", statePtr->inEofChar);
                Tcl_DStringAppendElement(dsPtr, buf);
            }
        }
        if (flags & TCL_WRITABLE) {
            if (chanPtr->outEofChar == 0) {
            if (statePtr->outEofChar == 0) {
                Tcl_DStringAppendElement(dsPtr, "");
            } else {
                char buf[4];

                sprintf(buf, "%c", chanPtr->outEofChar);
                sprintf(buf, "%c", statePtr->outEofChar);
                Tcl_DStringAppendElement(dsPtr, buf);
            }
        }
        if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
                (TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
            Tcl_DStringEndSublist(dsPtr);
        }

            Tcl_DStringAppendElement(dsPtr, "-translation");
        }
        if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
                (TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {
            Tcl_DStringStartSublist(dsPtr);
        }
        if (flags & TCL_READABLE) {
            if (chanPtr->inputTranslation == TCL_TRANSLATE_AUTO) {
            if (statePtr->inputTranslation == TCL_TRANSLATE_AUTO) {
                Tcl_DStringAppendElement(dsPtr, "auto");
            } else if (chanPtr->inputTranslation == TCL_TRANSLATE_CR) {
            } else if (statePtr->inputTranslation == TCL_TRANSLATE_CR) {
                Tcl_DStringAppendElement(dsPtr, "cr");
            } else if (chanPtr->inputTranslation == TCL_TRANSLATE_CRLF) {
            } else if (statePtr->inputTranslation == TCL_TRANSLATE_CRLF) {
                Tcl_DStringAppendElement(dsPtr, "crlf");
            } else {
                Tcl_DStringAppendElement(dsPtr, "lf");
            }
        }
        if (flags & TCL_WRITABLE) {
            if (chanPtr->outputTranslation == TCL_TRANSLATE_AUTO) {
            if (statePtr->outputTranslation == TCL_TRANSLATE_AUTO) {
                Tcl_DStringAppendElement(dsPtr, "auto");
            } else if (chanPtr->outputTranslation == TCL_TRANSLATE_CR) {
            } else if (statePtr->outputTranslation == TCL_TRANSLATE_CR) {
                Tcl_DStringAppendElement(dsPtr, "cr");
            } else if (chanPtr->outputTranslation == TCL_TRANSLATE_CRLF) {
            } else if (statePtr->outputTranslation == TCL_TRANSLATE_CRLF) {
                Tcl_DStringAppendElement(dsPtr, "crlf");
            } else {
                Tcl_DStringAppendElement(dsPtr, "lf");
            }
        }
        if (((flags & (TCL_READABLE|TCL_WRITABLE)) ==
                (TCL_READABLE|TCL_WRITABLE)) && (len == 0)) {

Tcl_SetChannelOption(interp, chan, optionName, newValue)
    Tcl_Interp *interp;		/* For error reporting - can be NULL. */
    Tcl_Channel chan;		/* Channel on which to set mode. */
    char *optionName;		/* Which option to set? */
    char *newValue;		/* New value for option. */
{
    int newMode;		/* New (numeric) mode to sert. */
    Channel *chanPtr;		/* The real IO channel. */
    Channel *chanPtr = (Channel *) chan;	/* The real IO channel. */
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    size_t len;			/* Length of optionName string. */
    int argc;
    char **argv;
    
    chanPtr = (Channel *) chan;

    /*
     * If the channel is in the middle of a background copy, fail.
     */

    if (chanPtr->csPtr) {
    if (statePtr->csPtr) {
	if (interp) {
	    Tcl_AppendResult(interp,
		    "unable to set channel options: background copy in progress",
		    (char *) NULL);
	}
        return TCL_ERROR;
    }


    /*
     * Disallow options on dead channels -- channels that have been closed but
     * not yet been deallocated. Such channels can be found if the exit
     * handler for channel cleanup has run but the channel is still
     * registered in an interpreter.
     */

    if (CheckForDeadChannel(NULL,chanPtr)) return TCL_ERROR;
    
    if (CheckForDeadChannel(NULL, statePtr)) {
	return TCL_ERROR;
    }

    /*
     * This operation should occur at the top of a channel stack.
     */

    chanPtr = statePtr->topChanPtr;

    len = strlen(optionName);

    if ((len > 2) && (optionName[1] == 'b') &&
            (strncmp(optionName, "-blocking", len) == 0)) {
        if (Tcl_GetBoolean(interp, newValue, &newMode) == TCL_ERROR) {
            return TCL_ERROR;
        }
        if (newMode) {
            newMode = TCL_MODE_BLOCKING;
        } else {
            newMode = TCL_MODE_NONBLOCKING;
        }
	return SetBlockMode(interp, chanPtr, newMode);
    } else if ((len > 7) && (optionName[1] == 'b') &&
            (strncmp(optionName, "-buffering", len) == 0)) {
        len = strlen(newValue);
        if ((newValue[0] == 'f') && (strncmp(newValue, "full", len) == 0)) {
            chanPtr->flags &=
            statePtr->flags &=
                (~(CHANNEL_UNBUFFERED|CHANNEL_LINEBUFFERED));
        } else if ((newValue[0] == 'l') &&
                (strncmp(newValue, "line", len) == 0)) {
            chanPtr->flags &= (~(CHANNEL_UNBUFFERED));
            chanPtr->flags |= CHANNEL_LINEBUFFERED;
            statePtr->flags &= (~(CHANNEL_UNBUFFERED));
            statePtr->flags |= CHANNEL_LINEBUFFERED;
        } else if ((newValue[0] == 'n') &&
                (strncmp(newValue, "none", len) == 0)) {
            chanPtr->flags &= (~(CHANNEL_LINEBUFFERED));
            chanPtr->flags |= CHANNEL_UNBUFFERED;
            statePtr->flags &= (~(CHANNEL_LINEBUFFERED));
            statePtr->flags |= CHANNEL_UNBUFFERED;
        } else {
            if (interp) {
                Tcl_AppendResult(interp, "bad value for -buffering: ",
                        "must be one of full, line, or none",
                        (char *) NULL);
                return TCL_ERROR;
            }
        }
	return TCL_OK;
    } else if ((len > 7) && (optionName[1] == 'b') &&
            (strncmp(optionName, "-buffersize", len) == 0)) {
        chanPtr->bufSize = atoi(newValue);	/* INTL: "C", UTF safe. */
        if ((chanPtr->bufSize < 10) || (chanPtr->bufSize > (1024 * 1024))) {
            chanPtr->bufSize = CHANNELBUFFER_DEFAULT_SIZE;
        statePtr->bufSize = atoi(newValue);	/* INTL: "C", UTF safe. */
        if ((statePtr->bufSize < 10) || (statePtr->bufSize > (1024 * 1024))) {
            statePtr->bufSize = CHANNELBUFFER_DEFAULT_SIZE;
        }
    } else if ((len > 2) && (optionName[1] == 'e') &&
	    (strncmp(optionName, "-encoding", len) == 0)) {
	Tcl_Encoding encoding;

	if ((newValue[0] == '\0') || (strcmp(newValue, "binary") == 0)) {
	    encoding = NULL;
	} else {
	    encoding = Tcl_GetEncoding(interp, newValue);
	    if (encoding == NULL) {
		return TCL_ERROR;
	    }
	}
	Tcl_FreeEncoding(chanPtr->encoding);
	chanPtr->encoding = encoding;
	chanPtr->inputEncodingState = NULL;
	chanPtr->inputEncodingFlags = TCL_ENCODING_START;
	chanPtr->outputEncodingState = NULL;
	chanPtr->outputEncodingFlags = TCL_ENCODING_START;
	chanPtr->flags &= ~CHANNEL_NEED_MORE_DATA;
	Tcl_FreeEncoding(statePtr->encoding);
	statePtr->encoding = encoding;
	statePtr->inputEncodingState = NULL;
	statePtr->inputEncodingFlags = TCL_ENCODING_START;
	statePtr->outputEncodingState = NULL;
	statePtr->outputEncodingFlags = TCL_ENCODING_START;
	statePtr->flags &= ~CHANNEL_NEED_MORE_DATA;
	UpdateInterest(chanPtr);
    } else if ((len > 2) && (optionName[1] == 'e') &&
            (strncmp(optionName, "-eofchar", len) == 0)) {
        if (Tcl_SplitList(interp, newValue, &argc, &argv) == TCL_ERROR) {
            return TCL_ERROR;
        }
        if (argc == 0) {
            chanPtr->inEofChar = 0;
            chanPtr->outEofChar = 0;
            statePtr->inEofChar = 0;
            statePtr->outEofChar = 0;
        } else if (argc == 1) {
            if (chanPtr->flags & TCL_WRITABLE) {
                chanPtr->outEofChar = (int) argv[0][0];
            if (statePtr->flags & TCL_WRITABLE) {
                statePtr->outEofChar = (int) argv[0][0];
            }
            if (chanPtr->flags & TCL_READABLE) {
                chanPtr->inEofChar = (int) argv[0][0];
            if (statePtr->flags & TCL_READABLE) {
                statePtr->inEofChar = (int) argv[0][0];
            }
        } else if (argc != 2) {
            if (interp) {
                Tcl_AppendResult(interp,
                        "bad value for -eofchar: should be a list of one or",
                        " two elements", (char *) NULL);
            }
            ckfree((char *) argv);
            return TCL_ERROR;
        } else {
            if (chanPtr->flags & TCL_READABLE) {
                chanPtr->inEofChar = (int) argv[0][0];
            if (statePtr->flags & TCL_READABLE) {
                statePtr->inEofChar = (int) argv[0][0];
            }
            if (chanPtr->flags & TCL_WRITABLE) {
                chanPtr->outEofChar = (int) argv[1][0];
            if (statePtr->flags & TCL_WRITABLE) {
                statePtr->outEofChar = (int) argv[1][0];
            }
        }
        if (argv != (char **) NULL) {
            ckfree((char *) argv);
        }
	return TCL_OK;
    } else if ((len > 1) && (optionName[1] == 't') &&
            (strncmp(optionName, "-translation", len) == 0)) {
	char *readMode, *writeMode;

        if (Tcl_SplitList(interp, newValue, &argc, &argv) == TCL_ERROR) {
            return TCL_ERROR;
        }

        if (argc == 1) {
	    readMode = (chanPtr->flags & TCL_READABLE) ? argv[0] : NULL;
	    writeMode = (chanPtr->flags & TCL_WRITABLE) ? argv[0] : NULL;
	    readMode = (statePtr->flags & TCL_READABLE) ? argv[0] : NULL;
	    writeMode = (statePtr->flags & TCL_WRITABLE) ? argv[0] : NULL;
	} else if (argc == 2) {
	    readMode = (chanPtr->flags & TCL_READABLE) ? argv[0] : NULL;
	    writeMode = (chanPtr->flags & TCL_WRITABLE) ? argv[1] : NULL;
	    readMode = (statePtr->flags & TCL_READABLE) ? argv[0] : NULL;
	    writeMode = (statePtr->flags & TCL_WRITABLE) ? argv[1] : NULL;
	} else {
            if (interp) {
                Tcl_AppendResult(interp,
                        "bad value for -translation: must be a one or two",
                        " element list", (char *) NULL);
            }
            ckfree((char *) argv);
            return TCL_ERROR;
	}

	if (readMode) {
	    if (*readMode == '\0') {
		newMode = chanPtr->inputTranslation;
		newMode = statePtr->inputTranslation;
	    } else if (strcmp(readMode, "auto") == 0) {
		newMode = TCL_TRANSLATE_AUTO;
	    } else if (strcmp(readMode, "binary") == 0) {
		newMode = TCL_TRANSLATE_LF;
		chanPtr->inEofChar = 0;
		Tcl_FreeEncoding(chanPtr->encoding);		    
		chanPtr->encoding = NULL;
		statePtr->inEofChar = 0;
		Tcl_FreeEncoding(statePtr->encoding);		    
		statePtr->encoding = NULL;
	    } else if (strcmp(readMode, "lf") == 0) {
		newMode = TCL_TRANSLATE_LF;
	    } else if (strcmp(readMode, "cr") == 0) {
		newMode = TCL_TRANSLATE_CR;
	    } else if (strcmp(readMode, "crlf") == 0) {
		newMode = TCL_TRANSLATE_CRLF;
	    } else if (strcmp(readMode, "platform") == 0) {

	    /*
	     * Reset the EOL flags since we need to look at any buffered
	     * data to see if the new translation mode allows us to
	     * complete the line.
	     */

	    if (newMode != chanPtr->inputTranslation) {
		chanPtr->inputTranslation = (Tcl_EolTranslation) newMode;
		chanPtr->flags &= ~(INPUT_SAW_CR);
		chanPtr->flags &= ~(CHANNEL_NEED_MORE_DATA);
	    if (newMode != statePtr->inputTranslation) {
		statePtr->inputTranslation = (Tcl_EolTranslation) newMode;
		statePtr->flags &= ~(INPUT_SAW_CR);
		statePtr->flags &= ~(CHANNEL_NEED_MORE_DATA);
		UpdateInterest(chanPtr);
	    }
	}
	if (writeMode) {
	    if (*writeMode == '\0') {
		/* Do nothing. */
	    } else if (strcmp(writeMode, "auto") == 0) {
		/*
		 * This is a hack to get TCP sockets to produce output
		 * in CRLF mode if they are being set into AUTO mode.
		 * A better solution for achieving this effect will be
		 * coded later.
		 */

		if (strcmp(chanPtr->typePtr->typeName, "tcp") == 0) {
		    chanPtr->outputTranslation = TCL_TRANSLATE_CRLF;
		    statePtr->outputTranslation = TCL_TRANSLATE_CRLF;
		} else {
		    chanPtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
		    statePtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
		}
	    } else if (strcmp(writeMode, "binary") == 0) {
		chanPtr->outEofChar = 0;
		chanPtr->outputTranslation = TCL_TRANSLATE_LF;
		Tcl_FreeEncoding(chanPtr->encoding);		    
		chanPtr->encoding = NULL;
		statePtr->outEofChar = 0;
		statePtr->outputTranslation = TCL_TRANSLATE_LF;
		Tcl_FreeEncoding(statePtr->encoding);		    
		statePtr->encoding = NULL;
	    } else if (strcmp(writeMode, "lf") == 0) {
		chanPtr->outputTranslation = TCL_TRANSLATE_LF;
		statePtr->outputTranslation = TCL_TRANSLATE_LF;
	    } else if (strcmp(writeMode, "cr") == 0) {
		chanPtr->outputTranslation = TCL_TRANSLATE_CR;
		statePtr->outputTranslation = TCL_TRANSLATE_CR;
	    } else if (strcmp(writeMode, "crlf") == 0) {
		chanPtr->outputTranslation = TCL_TRANSLATE_CRLF;
		statePtr->outputTranslation = TCL_TRANSLATE_CRLF;
	    } else if (strcmp(writeMode, "platform") == 0) {
		chanPtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
		statePtr->outputTranslation = TCL_PLATFORM_TRANSLATION;
	    } else {
		if (interp) {
		    Tcl_AppendResult(interp,
			    "bad value for -translation: ",
			    "must be one of auto, binary, cr, lf, crlf,",
			    " or platform", (char *) NULL);
		}

	return Tcl_BadChannelOption(interp, optionName, (char *) NULL);
    }

    /*
     * If bufsize changes, need to get rid of old utility buffer.
     */

    if (chanPtr->saveInBufPtr != NULL) {
	RecycleBuffer(chanPtr, chanPtr->saveInBufPtr, 1);
	chanPtr->saveInBufPtr = NULL;
    if (statePtr->saveInBufPtr != NULL) {
	RecycleBuffer(statePtr, statePtr->saveInBufPtr, 1);
	statePtr->saveInBufPtr = NULL;
    }
    if (chanPtr->inQueueHead != NULL) {
	if ((chanPtr->inQueueHead->nextPtr == NULL)
		&& (chanPtr->inQueueHead->nextAdded ==
			chanPtr->inQueueHead->nextRemoved)) {
	    RecycleBuffer(chanPtr, chanPtr->inQueueHead, 1);
	    chanPtr->inQueueHead = NULL;
	    chanPtr->inQueueTail = NULL;
    if (statePtr->inQueueHead != NULL) {
	if ((statePtr->inQueueHead->nextPtr == NULL)
		&& (statePtr->inQueueHead->nextAdded ==
			statePtr->inQueueHead->nextRemoved)) {
	    RecycleBuffer(statePtr, statePtr->inQueueHead, 1);
	    statePtr->inQueueHead = NULL;
	    statePtr->inQueueTail = NULL;
	}
    }

    /*
     * If encoding or bufsize changes, need to update output staging buffer.
     */

    if (chanPtr->outputStage != NULL) {
	ckfree((char *) chanPtr->outputStage);
	chanPtr->outputStage = NULL;
    if (statePtr->outputStage != NULL) {
	ckfree((char *) statePtr->outputStage);
	statePtr->outputStage = NULL;
    }
    if ((chanPtr->encoding != NULL) && (chanPtr->flags & TCL_WRITABLE)) {
	chanPtr->outputStage = (char *) 
	    ckalloc((unsigned) (chanPtr->bufSize + 2));
    if ((statePtr->encoding != NULL) && (statePtr->flags & TCL_WRITABLE)) {
	statePtr->outputStage = (char *) 
	    ckalloc((unsigned) (statePtr->bufSize + 2));
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *

 */

static void
CleanupChannelHandlers(interp, chanPtr)
    Tcl_Interp *interp;
    Channel *chanPtr;
{
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    EventScriptRecord *sPtr, *prevPtr, *nextPtr;

    /*
     * Remove fileevent records on this channel that refer to the
     * given interpreter.
     */
    
    for (sPtr = chanPtr->scriptRecordPtr,
    for (sPtr = statePtr->scriptRecordPtr,
             prevPtr = (EventScriptRecord *) NULL;
	 sPtr != (EventScriptRecord *) NULL;
	 sPtr = nextPtr) {
        nextPtr = sPtr->nextPtr;
        if (sPtr->interp == interp) {
            if (prevPtr == (EventScriptRecord *) NULL) {
                chanPtr->scriptRecordPtr = nextPtr;
                statePtr->scriptRecordPtr = nextPtr;
            } else {
                prevPtr->nextPtr = nextPtr;
            }

            Tcl_DeleteChannelHandler((Tcl_Channel) chanPtr,
                    ChannelEventScriptInvoker, (ClientData) sPtr);
                    TclChannelEventScriptInvoker, (ClientData) sPtr);

	    Tcl_DecrRefCount(sPtr->scriptPtr);
            ckfree((char *) sPtr);
        } else {
            prevPtr = sPtr;
        }
    }

Tcl_NotifyChannel(channel, mask)
    Tcl_Channel channel;	/* Channel that detected an event. */
    int mask;			/* OR'ed combination of TCL_READABLE,
				 * TCL_WRITABLE, or TCL_EXCEPTION: indicates
				 * which events were detected. */
{
    Channel *chanPtr = (Channel *) channel;
    ChannelState *statePtr = chanPtr->state;	/* state info for channel */
    ChannelHandler *chPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);
    NextChannelHandler nh;
#ifdef TCL_CHANNEL_VERSION_2
    Channel* upChanPtr;
    Tcl_ChannelType* upTypePtr;

    /*
     * In contrast to the other API functions this procedure walks towards
     * the top of a stack and not down from it.
     *
     * The channel calling this procedure is the one who generated the event,
     * and thus does not take part in handling it. IOW, its HandlerProc is
     * not called, instead we begin with the channel above it.
     *
     * This behaviour also allows the transformation channels to
     * generate their own events and pass them upward.
     */

    while (mask && (chanPtr->upChanPtr != ((Channel*) NULL))) {
        upChanPtr = chanPtr->upChanPtr;
	upTypePtr = upChanPtr->typePtr;

	if ((Tcl_ChannelVersion(upTypePtr) == TCL_CHANNEL_VERSION_2) &&
		(Tcl_ChannelHandlerProc(upTypePtr) !=
			((Tcl_DriverHandlerProc *) NULL))) {

	    Tcl_DriverHandlerProc* handlerProc =
		Tcl_ChannelHandlerProc(upTypePtr);

	  mask = (*handlerProc) (upChanPtr->instanceData, mask);
	}

	/* ELSE:
	 * Ignore transformations which are unable to handle the event
	 * coming from below. Assume that they don't change the mask and
	 * pass it on.
	 */

	chanPtr = upChanPtr;
    }

    channel = (Tcl_Channel) chanPtr;

    /*
     * Here we have either reached the top of the stack or the mask is
     * empty.  We break out of the procedure if it is the latter.
     */

    if (!mask) {
        return;
    }

    /*
     * We are now above the topmost channel in a stack and have events
     * left. Now call the channel handlers as usual.
     *
     * Preserve the channel struct in case the script closes it.
     */
     
    Tcl_Preserve((ClientData) channel);

    /*
     * If we are flushing in the background, be sure to call FlushChannel
     * for writable events.  Note that we have to discard the writable
     * event so we don't call any write handlers before the flush is
     * complete.
     */

    if ((statePtr->flags & BG_FLUSH_SCHEDULED) && (mask & TCL_WRITABLE)) {
      FlushChannel(NULL, chanPtr, 1);
      mask &= ~TCL_WRITABLE;
    }

    /*
     * Add this invocation to the list of recursive invocations of
     * ChannelHandlerEventProc.
     */
    
    nh.nextHandlerPtr = (ChannelHandler *) NULL;
    nh.nestedHandlerPtr = tsdPtr->nestedHandlerPtr;
    tsdPtr->nestedHandlerPtr = &nh;

    for (chPtr = statePtr->chPtr; chPtr != (ChannelHandler *) NULL; ) {

      /*
       * If this channel handler is interested in any of the events that
       * have occurred on the channel, invoke its procedure.
       */
        
      if ((chPtr->mask & mask) != 0) {
	nh.nextHandlerPtr = chPtr->nextPtr;
	(*(chPtr->proc))(chPtr->clientData, mask);
	chPtr = nh.nextHandlerPtr;
      } else {
	chPtr = chPtr->nextPtr;
      }
    }

    /*
     * Update the notifier interest, since it may have changed after
     * invoking event handlers. Skip that if the channel was deleted
     * in the call to the channel handler.
     */

    if (chanPtr->typePtr != NULL) {
        UpdateInterest(chanPtr);
    }

    Tcl_Release((ClientData) channel);

    tsdPtr->nestedHandlerPtr = nh.nestedHandlerPtr;
#else
    /* Walk all channels in a stack ! and notify them in order.
     */

    while (chanPtr !=  (Channel *) NULL) {
    while (chanPtr != (Channel *) NULL) {
        /*
	 * Preserve the channel struct in case the script closes it.
	 */
     
        Tcl_Preserve((ClientData) channel);

	/*
	 * If we are flushing in the background, be sure to call FlushChannel
	 * for writable events.  Note that we have to discard the writable
	 * event so we don't call any write handlers before the flush is
	 * complete.
	 */

	if ((chanPtr->flags & BG_FLUSH_SCHEDULED) && (mask & TCL_WRITABLE)) {
	if ((statePtr->flags & BG_FLUSH_SCHEDULED) && (mask & TCL_WRITABLE)) {
	    FlushChannel(NULL, chanPtr, 1);
	    mask &= ~TCL_WRITABLE;
	}

	/*
	 * Add this invocation to the list of recursive invocations of
	 * ChannelHandlerEventProc.
	 */
    
	nh.nextHandlerPtr = (ChannelHandler *) NULL;
	nh.nestedHandlerPtr = tsdPtr->nestedHandlerPtr;
	tsdPtr->nestedHandlerPtr = &nh;
    
	for (chPtr = chanPtr->chPtr; chPtr != (ChannelHandler *) NULL; ) {

	for (chPtr = statePtr->chPtr; chPtr != (ChannelHandler *) NULL; ) {

	    /*
	     * If this channel handler is interested in any of the events that
	     * have occurred on the channel, invoke its procedure.
	     */
        
	    if ((chPtr->mask & mask) != 0) {