/* 
 * tclCompExpr.c --
 *
 *	This file contains the code to compile Tcl expressions.
 *
 * Copyright (c) 1997 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: tclCompExpr.c,v 1.14.2.2 2003/10/16 02:28:01 dgp Exp $
 * RCS: @(#) $Id: tclCompExpr.c,v 1.14.2.3 2004/02/07 05:48:00 dgp Exp $
 */

#include "tclInt.h"
#include "tclCompile.h"

/*
 * The stuff below is a bit of a hack so that this file can be used in

    Tcl_HashEntry *hPtr;
    CONST char *operator;
    Tcl_DString opBuf;
    int objIndex, opIndex, length, code;
    char buffer[TCL_UTF_MAX];

    if (exprTokenPtr->type != TCL_TOKEN_SUB_EXPR) {
	panic("CompileSubExpr: token type %d not TCL_TOKEN_SUB_EXPR\n",
	Tcl_Panic("CompileSubExpr: token type %d not TCL_TOKEN_SUB_EXPR\n",
	        exprTokenPtr->type);
    }
    code = TCL_OK;

    /*
     * Switch on the type of the first token after the subexpression token.
     * After processing it, advance tokenPtr to point just after the

		    if (code != TCL_OK) {
			goto done;
		    }
		    tokenPtr = endPtr;
		    break;
		    
		default:
		    panic("CompileSubExpr: unexpected operator %d requiring special treatment\n",
		    Tcl_Panic("CompileSubExpr: unexpected operator %d requiring special treatment\n",
		        opIndex);
	    } /* end switch on operator requiring special treatment */
	    infoPtr->hasOperators = 1;
	    break;

        default:
	    panic("CompileSubExpr: unexpected token type %d\n",
	    Tcl_Panic("CompileSubExpr: unexpected token type %d\n",
	            tokenPtr->type);
    }

    /*
     * Verify that the subexpression token had the required number of
     * subtokens: that we've advanced tokenPtr just beyond the
     * subexpression's last token. For example, a "*" subexpression must

    CompileEnv *envPtr;		 /* Holds resulting instructions. */
    Tcl_Token **endPtrPtr;	 /* If successful, a pointer to the token
				  * just after the last token in the
				  * subexpression is stored here. */
{
    JumpFixup shortCircuitFixup; /* Used to fix up the short circuit jump
				  * after the first subexpression. */
    JumpFixup lhsTrueFixup, lhsEndFixup;
    				 /* Used to fix up jumps used to convert the
    JumpFixup shortCircuitFixup2;/* Used to fix up the second jump to the
				  * short-circuit target. */
    JumpFixup endFixup;          /* Used to fix up jump to the end. */
				  * first operand to 0 or 1. */
    Tcl_Token *tokenPtr;
    int dist, code;
    int code;
    int savedStackDepth = envPtr->currStackDepth;

    /*
     * Emit code for the first operand.
     */

    tokenPtr = exprTokenPtr+2;
    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
	goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);

    /*
     * Convert the first operand to the result that Tcl requires:
     * "0" or "1". Eventually we'll use a new instruction for this.
     */
    
     * Emit the short-circuit jump.
    TclEmitForwardJump(envPtr, TCL_TRUE_JUMP, &lhsTrueFixup);
    TclEmitPush(TclRegisterNewLiteral(envPtr, "0", 1), envPtr);
    TclEmitForwardJump(envPtr, TCL_UNCONDITIONAL_JUMP, &lhsEndFixup);
    dist = (envPtr->codeNext - envPtr->codeStart) - lhsTrueFixup.codeOffset;
    if (TclFixupForwardJump(envPtr, &lhsTrueFixup, dist, 127)) {
        badDist:
	panic("CompileLandOrLorExpr: bad jump distance %d\n", dist);
    }
    envPtr->currStackDepth = savedStackDepth;
    TclEmitPush(TclRegisterNewLiteral(envPtr, "1", 1), envPtr);
    dist = (envPtr->codeNext - envPtr->codeStart) - lhsEndFixup.codeOffset;
    if (TclFixupForwardJump(envPtr, &lhsEndFixup, dist, 127)) {
	goto badDist;
    }

    /*
     * Emit the "short circuit" jump around the rest of the expression.
     * Duplicate the "0" or "1" on top of the stack first to keep the
     * jump from consuming it.
     */

    TclEmitOpcode(INST_DUP, envPtr);
    TclEmitForwardJump(envPtr,
	    ((opIndex==OP_LAND)? TCL_FALSE_JUMP : TCL_TRUE_JUMP),
	    &shortCircuitFixup);

    /*
     * Emit code for the second operand.
     */

    code = CompileSubExpr(tokenPtr, infoPtr, envPtr);
    if (code != TCL_OK) {
	goto done;
    }
    tokenPtr += (tokenPtr->numComponents + 1);

	    
    /*
     * Emit a "logical and" or "logical or" instruction. This does not try
     * to "short- circuit" the evaluation of both operands, but instead
     * ensures that we either have a "1" or a "0" result.
     * The result is the boolean value of the second operand. We 
     * code this in a somewhat contorted manner to be able to reuse
     * the shortCircuit value and save one INST_JUMP.
     */

    TclEmitForwardJump(envPtr,
    TclEmitOpcode(((opIndex==OP_LAND)? INST_LAND : INST_LOR), envPtr);
	    ((opIndex==OP_LAND)? TCL_FALSE_JUMP : TCL_TRUE_JUMP),
	    &shortCircuitFixup2);

    if (opIndex == OP_LAND) {
	TclEmitPush(TclRegisterNewLiteral(envPtr, "1", 1), envPtr);
    } else {
	TclEmitPush(TclRegisterNewLiteral(envPtr, "0", 1), envPtr);
    }
    TclEmitForwardJump(envPtr, TCL_UNCONDITIONAL_JUMP, &endFixup);

    /*
     * Fixup the short-circuit jumps and push the shortCircuit value.
     * Note that shortCircuitFixup2 is always a short jump.
     */
     * Now that we know the target of the forward jump, update it with the

     * correct distance.
     */

    dist = (envPtr->codeNext - envPtr->codeStart)
	    - shortCircuitFixup.codeOffset;
    TclFixupForwardJump(envPtr, &shortCircuitFixup, dist, 127);
    TclFixupForwardJumpToHere(envPtr, &shortCircuitFixup2, 127);
    if (TclFixupForwardJumpToHere(envPtr, &shortCircuitFixup, 127)) {
	/*
	 * shortCircuit jump grown by 3 bytes: update endFixup.
	 */
	    
	 endFixup.codeOffset += 3;
    }

    if (opIndex == OP_LAND) {
	TclEmitPush(TclRegisterNewLiteral(envPtr, "0", 1), envPtr);
    } else {
	TclEmitPush(TclRegisterNewLiteral(envPtr, "1", 1), envPtr);
    }

    TclFixupForwardJumpToHere(envPtr, &endFixup, 127);
    *endPtrPtr = tokenPtr;

    done:
    envPtr->currStackDepth = savedStackDepth + 1;
    return code;
}