tclresult.c

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/* 
 * tclResult.c --
 *
 *	This file contains code to manage the interpreter result.
 *
 * Copyright (c) 1997 by 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: tclResult.c,v 1.5 2002/01/25 20:40:55 dgp Exp $
 */

#include "tclInt.h"

/*
 * Function prototypes for local procedures in this file:
 */

static void             ResetObjResult _ANSI_ARGS_((Interp *iPtr));
static void		SetupAppendBuffer _ANSI_ARGS_((Interp *iPtr,
			    int newSpace));


/*
 *----------------------------------------------------------------------
 *
 * Tcl_SaveResult --
 *
 *      Takes a snapshot of the current result state of the interpreter.
 *      The snapshot can be restored at any point by
 *      Tcl_RestoreResult. Note that this routine does not 
 *	preserve the errorCode, errorInfo, or flags fields so it
 *	should not be used if an error is in progress.
 *
 *      Once a snapshot is saved, it must be restored by calling
 *      Tcl_RestoreResult, or discarded by calling
 *      Tcl_DiscardResult.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	Resets the interpreter result.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SaveResult(interp, statePtr)
    Tcl_Interp *interp;		/* Interpreter to save. */
    Tcl_SavedResult *statePtr;	/* Pointer to state structure. */
{
    Interp *iPtr = (Interp *) interp;

    /*
     * Move the result object into the save state.  Note that we don't need
     * to change its refcount because we're moving it, not adding a new
     * reference.  Put an empty object into the interpreter.
     */

    statePtr->objResultPtr = iPtr->objResultPtr;
    iPtr->objResultPtr = Tcl_NewObj(); 
    Tcl_IncrRefCount(iPtr->objResultPtr); 

    /*
     * Save the string result. 
     */

    statePtr->freeProc = iPtr->freeProc;
    if (iPtr->result == iPtr->resultSpace) {
	/*
	 * Copy the static string data out of the interp buffer.
	 */

	statePtr->result = statePtr->resultSpace;
	strcpy(statePtr->result, iPtr->result);
	statePtr->appendResult = NULL;
    } else if (iPtr->result == iPtr->appendResult) {
	/*
	 * Move the append buffer out of the interp.
	 */

	statePtr->appendResult = iPtr->appendResult;
	statePtr->appendAvl = iPtr->appendAvl;
	statePtr->appendUsed = iPtr->appendUsed;
	statePtr->result = statePtr->appendResult;
	iPtr->appendResult = NULL;
	iPtr->appendAvl = 0;
	iPtr->appendUsed = 0;
    } else {
	/*
	 * Move the dynamic or static string out of the interpreter.
	 */

	statePtr->result = iPtr->result;
	statePtr->appendResult = NULL;
    }

    iPtr->result = iPtr->resultSpace;
    iPtr->resultSpace[0] = 0;
    iPtr->freeProc = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_RestoreResult --
 *
 *      Restores the state of the interpreter to a snapshot taken
 *      by Tcl_SaveResult.  After this call, the token for
 *      the interpreter state is no longer valid.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Restores the interpreter result.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_RestoreResult(interp, statePtr)
    Tcl_Interp* interp;		/* Interpreter being restored. */
    Tcl_SavedResult *statePtr;	/* State returned by Tcl_SaveResult. */
{
    Interp *iPtr = (Interp *) interp;

    Tcl_ResetResult(interp);

    /*
     * Restore the string result.
     */

    iPtr->freeProc = statePtr->freeProc;
    if (statePtr->result == statePtr->resultSpace) {
	/*
	 * Copy the static string data into the interp buffer.
	 */

	iPtr->result = iPtr->resultSpace;
	strcpy(iPtr->result, statePtr->result);
    } else if (statePtr->result == statePtr->appendResult) {
	/*
	 * Move the append buffer back into the interp.
	 */

	if (iPtr->appendResult != NULL) {
	    ckfree((char *)iPtr->appendResult);
	}

	iPtr->appendResult = statePtr->appendResult;
	iPtr->appendAvl = statePtr->appendAvl;
	iPtr->appendUsed = statePtr->appendUsed;
	iPtr->result = iPtr->appendResult;
    } else {
	/*
	 * Move the dynamic or static string back into the interpreter.
	 */

	iPtr->result = statePtr->result;
    }

    /*
     * Restore the object result.
     */

    Tcl_DecrRefCount(iPtr->objResultPtr);
    iPtr->objResultPtr = statePtr->objResultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_DiscardResult --
 *
 *      Frees the memory associated with an interpreter snapshot
 *      taken by Tcl_SaveResult.  If the snapshot is not
 *      restored, this procedure must be called to discard it,
 *      or the memory will be lost.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_DiscardResult(statePtr)
    Tcl_SavedResult *statePtr;	/* State returned by Tcl_SaveResult. */
{
    TclDecrRefCount(statePtr->objResultPtr);

    if (statePtr->result == statePtr->appendResult) {
	ckfree(statePtr->appendResult);
    } else if (statePtr->freeProc) {
	if ((statePtr->freeProc == TCL_DYNAMIC)
	        || (statePtr->freeProc == (Tcl_FreeProc *) free)) {
	    ckfree(statePtr->result);
	} else {
	    (*statePtr->freeProc)(statePtr->result);
	}
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetResult --
 *
 *	Arrange for "string" to be the Tcl return value.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	interp->result is left pointing either to "string" (if "copy" is 0)
 *	or to a copy of string. Also, the object result is reset.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetResult(interp, string, freeProc)
    Tcl_Interp *interp;		/* Interpreter with which to associate the
				 * return value. */
    register char *string;	/* Value to be returned.  If NULL, the
				 * result is set to an empty string. */
    Tcl_FreeProc *freeProc;	/* Gives information about the string:
				 * TCL_STATIC, TCL_VOLATILE, or the address
				 * of a Tcl_FreeProc such as free. */
{
    Interp *iPtr = (Interp *) interp;
    int length;
    register Tcl_FreeProc *oldFreeProc = iPtr->freeProc;
    char *oldResult = iPtr->result;

    if (string == NULL) {
	iPtr->resultSpace[0] = 0;
	iPtr->result = iPtr->resultSpace;
	iPtr->freeProc = 0;
    } else if (freeProc == TCL_VOLATILE) {
	length = strlen(string);
	if (length > TCL_RESULT_SIZE) {
	    iPtr->result = (char *) ckalloc((unsigned) length+1);
	    iPtr->freeProc = TCL_DYNAMIC;
	} else {
	    iPtr->result = iPtr->resultSpace;
	    iPtr->freeProc = 0;
	}
	strcpy(iPtr->result, string);
    } else {
	iPtr->result = string;
	iPtr->freeProc = freeProc;
    }

    /*
     * If the old result was dynamically-allocated, free it up.  Do it
     * here, rather than at the beginning, in case the new result value
     * was part of the old result value.
     */

    if (oldFreeProc != 0) {
	if ((oldFreeProc == TCL_DYNAMIC)
		|| (oldFreeProc == (Tcl_FreeProc *) free)) {
	    ckfree(oldResult);
	} else {
	    (*oldFreeProc)(oldResult);
	}
    }

    /*
     * Reset the object result since we just set the string result.
     */

    ResetObjResult(iPtr);
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetStringResult --
 *
 *	Returns an interpreter's result value as a string.
 *
 * Results:
 *	The interpreter's result as a string.
 *
 * Side effects:
 *	If the string result is empty, the object result is moved to the
 *	string result, then the object result is reset.
 *
 *----------------------------------------------------------------------
 */

CONST char *
Tcl_GetStringResult(interp)
     register Tcl_Interp *interp; /* Interpreter whose result to return. */
{
    /*
     * If the string result is empty, move the object result to the
     * string result, then reset the object result.
     */
    
    if (*(interp->result) == 0) {
	Tcl_SetResult(interp, TclGetString(Tcl_GetObjResult(interp)),
	        TCL_VOLATILE);
    }
    return interp->result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_SetObjResult --
 *
 *	Arrange for objPtr to be an interpreter's result value.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	interp->objResultPtr is left pointing to the object referenced
 *	by objPtr. The object's reference count is incremented since
 *	there is now a new reference to it. The reference count for any
 *	old objResultPtr value is decremented. Also, the string result
 *	is reset.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_SetObjResult(interp, objPtr)
    Tcl_Interp *interp;		/* Interpreter with which to associate the
				 * return object value. */
    register Tcl_Obj *objPtr;	/* Tcl object to be returned. If NULL, the
				 * obj result is made an empty string
				 * object. */
{
    register Interp *iPtr = (Interp *) interp;
    register Tcl_Obj *oldObjResult = iPtr->objResultPtr;

    iPtr->objResultPtr = objPtr;
    Tcl_IncrRefCount(objPtr);	/* since interp result is a reference */

    /*
     * We wait until the end to release the old object result, in case
     * we are setting the result to itself.
     */
    
    TclDecrRefCount(oldObjResult);

    /*
     * Reset the string result since we just set the result object.
     */

    if (iPtr->freeProc != NULL) {
	if ((iPtr->freeProc == TCL_DYNAMIC)
	        || (iPtr->freeProc == (Tcl_FreeProc *) free)) {
	    ckfree(iPtr->result);
	} else {
	    (*iPtr->freeProc)(iPtr->result);
	}
	iPtr->freeProc = 0;
    }
    iPtr->result = iPtr->resultSpace;
    iPtr->resultSpace[0] = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetObjResult --
 *
 *	Returns an interpreter's result value as a Tcl object. The object's
 *	reference count is not modified; the caller must do that if it
 *	needs to hold on to a long-term reference to it.
 *
 * Results:
 *	The interpreter's result as an object.
 *
 * Side effects:
 *	If the interpreter has a non-empty string result, the result object
 *	is either empty or stale because some procedure set interp->result
 *	directly. If so, the string result is moved to the result object
 *	then the string result is reset.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
Tcl_GetObjResult(interp)
    Tcl_Interp *interp;		/* Interpreter whose result to return. */
{
    register Interp *iPtr = (Interp *) interp;
    Tcl_Obj *objResultPtr;
    int length;

    /*
     * If the string result is non-empty, move the string result to the
     * object result, then reset the string result.
     */
    
    if (*(iPtr->result) != 0) {
	ResetObjResult(iPtr);
	
	objResultPtr = iPtr->objResultPtr;
	length = strlen(iPtr->result);
	TclInitStringRep(objResultPtr, iPtr->result, length);
	
	if (iPtr->freeProc != NULL) {
	    if ((iPtr->freeProc == TCL_DYNAMIC)
	            || (iPtr->freeProc == (Tcl_FreeProc *) free)) {
		ckfree(iPtr->result);
	    } else {
		(*iPtr->freeProc)(iPtr->result);
	    }
	    iPtr->freeProc = 0;
	}
	iPtr->result = iPtr->resultSpace;
	iPtr->resultSpace[0] = 0;
    }
    return iPtr->objResultPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_AppendResultVA --
 *
 *	Append a variable number of strings onto the interpreter's string
 *	result.
 *
 * Results:
 *	None.
 *
 * Side effects:
 *	The result of the interpreter given by the first argument is
 *	extended by the strings in the va_list (up to a terminating NULL
 *	argument).
 *
 *	If the string result is empty, the object result is moved to the
 *	string result, then the object result is reset.
 *
 *----------------------------------------------------------------------
 */

void
Tcl_AppendResultVA (interp, argList)
    Tcl_Interp *interp;		/* Interpreter with which to associate the
				 * return value. */
    va_list argList;		/* Variable argument list. */
{
#define STATIC_LIST_SIZE 16
    Interp *iPtr = (Interp *) interp;
    char *string, *static_list[STATIC_LIST_SIZE];
    char **args = static_list;
    int nargs_space = STATIC_LIST_SIZE;
    int nargs, newSpace, i;

    /*
     * If the string result is empty, move the object result to the
     * string result, then reset the object result.
     */

    if (*(iPtr->result) == 0) {
	Tcl_SetResult((Tcl_Interp *) iPtr,
	        TclGetString(Tcl_GetObjResult((Tcl_Interp *) iPtr)),
	        TCL_VOLATILE);
    }
    
    /*
     * Scan through all the arguments to see how much space is needed
     * and save pointers to the arguments in the args array,
     * reallocating as necessary.
     */

    nargs = 0;
    newSpace = 0;
    while (1) {
 	string = va_arg(argList, char *);
	if (string == NULL) {
	    break;
	}
 	if (nargs >= nargs_space) {
 	    /* 
 	     * Expand the args buffer
 	     */
 	    nargs_space += STATIC_LIST_SIZE;
 	    if (args == static_list) {
 	    	args = (void *)ckalloc(nargs_space * sizeof(char *));
 		for (i = 0; i < nargs; ++i) {
 		    args[i] = static_list[i];
 		}
 	    } else {
 		args = (void *)ckrealloc((void *)args,
			nargs_space * sizeof(char *));
 	    }
 	}
  	newSpace += strlen(string);
	args[nargs++] = string;
    }

    /*
     * If the append buffer isn't already setup and large enough to hold
     * the new data, set it up.
     */

    if ((iPtr->result != iPtr->appendResult)
	    || (iPtr->appendResult[iPtr->appendUsed] != 0)
	    || ((newSpace + iPtr->appendUsed) >= iPtr->appendAvl)) {
       SetupAppendBuffer(iPtr, newSpace);
    }

    /*
     * Now go through all the argument strings again, copying them into the
     * buffer.
     */

    for (i = 0; i < nargs; ++i) {
 	string = args[i];
  	strcpy(iPtr->appendResult + iPtr->appendUsed, string);
  	iPtr->appendUsed += strlen(string);