*
 * Side effects:
 *	Consumes input from the socket.
 *
 *----------------------------------------------------------------------
 */

static size_t
TcpInputProc(
    ClientData instanceData,	/* The socket state. */
    char *buf,			/* Where to store data. */
    size_t toRead,			/* Maximum number of bytes to read. */
    int *errorCodePtr)		/* Where to store error codes. */
{
    SocketInfo *infoPtr = instanceData;
    size_t bytesRead;
    DWORD error;
    ThreadSpecificData *tsdPtr = TclThreadDataKeyGet(&dataKey);

    *errorCodePtr = 0;

    /*
     * Check that WinSock is initialized; do not call it if not, to prevent
     * system crashes. This can happen at exit time if the exit handler for
     * WinSock ran before other exit handlers that want to use sockets.
     */

    if (!SocketsEnabled()) {
	*errorCodePtr = EFAULT;
	return (size_t)-1;
    }

    /*
     * First check to see if EOF was already detected, to prevent calling the
     * socket stack after the first time EOF is detected.
     */

    if (infoPtr->flags & SOCKET_EOF) {
	return 0;
    }

    /*
     * Check to see if the socket is connected before trying to read.
     */

    if ((infoPtr->flags & SOCKET_ASYNC_CONNECT)
	    && !WaitForSocketEvent(infoPtr, FD_CONNECT, errorCodePtr)) {
	return (size_t)-1;
    }

    /*
     * No EOF, and it is connected, so try to read more from the socket. Note
     * that we clear the FD_READ bit because read events are level triggered
     * so a new event will be generated if there is still data available to be
     * read. We have to simulate blocking behavior here since we are always

	/*
	 * Check for error condition or underflow in non-blocking case.
	 */

	if ((infoPtr->flags & SOCKET_ASYNC) || (error != WSAEWOULDBLOCK)) {
	    TclWinConvertError(error);
	    *errorCodePtr = Tcl_GetErrno();
	    bytesRead = (size_t)-1;
	    break;
	}

	/*
	 * In the blocking case, wait until the file becomes readable or
	 * closed and try again.
	 */

	if (!WaitForSocketEvent(infoPtr, FD_READ|FD_CLOSE, errorCodePtr)) {
	    bytesRead = (size_t)-1;
	    break;
	}
    }

    SendMessage(tsdPtr->hwnd, SOCKET_SELECT, (WPARAM)SELECT, (LPARAM)infoPtr);

    return bytesRead;

 *
 * Side effects:
 *	Produces output on the socket.
 *
 *----------------------------------------------------------------------
 */

static size_t
TcpOutputProc(
    ClientData instanceData,	/* The socket state. */
    const char *buf,		/* Where to get data. */
    size_t toWrite,		/* Maximum number of bytes to write. */
    int *errorCodePtr)		/* Where to store error codes. */
{
    SocketInfo *infoPtr = instanceData;
    size_t bytesWritten;
    DWORD error;
    ThreadSpecificData *tsdPtr = TclThreadDataKeyGet(&dataKey);

    *errorCodePtr = 0;

    /*
     * Check that WinSock is initialized; do not call it if not, to prevent
     * system crashes. This can happen at exit time if the exit handler for
     * WinSock ran before other exit handlers that want to use sockets.
     */

    if (!SocketsEnabled()) {
	*errorCodePtr = EFAULT;
	return (size_t)-1;
    }

    /*
     * Check to see if the socket is connected before trying to write.
     */

    if ((infoPtr->flags & SOCKET_ASYNC_CONNECT)
	    && !WaitForSocketEvent(infoPtr, FD_CONNECT, errorCodePtr)) {
	return (size_t)-1;
    }

    while (1) {
	SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
		(WPARAM) UNSELECT, (LPARAM) infoPtr);

	/* single fd operation: this proc is only called for a connected socket. */

	 */

	error = WSAGetLastError();
	if (error == WSAEWOULDBLOCK) {
	    infoPtr->readyEvents &= ~(FD_WRITE);
	    if (infoPtr->flags & SOCKET_ASYNC) {
		*errorCodePtr = EAGAIN;
		bytesWritten = (size_t)-1;
		break;
	    }
	} else {
	    TclWinConvertError(error);
	    *errorCodePtr = Tcl_GetErrno();
	    bytesWritten = (size_t)-1;
	    break;
	}

	/*
	 * In the blocking case, wait until the file becomes writable or
	 * closed and try again.
	 */

	if (!WaitForSocketEvent(infoPtr, FD_WRITE|FD_CLOSE, errorCodePtr)) {
	    bytesWritten = (size_t)-1;
	    break;
	}
    }

    SendMessage(tsdPtr->hwnd, SOCKET_SELECT, (WPARAM)SELECT, (LPARAM)infoPtr);

    return bytesWritten;