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/*$Header$ */
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/*
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* tclPreserve.c --
|
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*
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* This file contains a collection of procedures that are used
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* to make sure that widget records and other data structures
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* aren't reallocated when there are nested procedures that
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* depend on their existence.
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*
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* Copyright (c) 1991-1994 The Regents of the University of California.
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* Copyright (c) 1994-1998 Sun Microsystems, Inc.
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*
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* See the file "license.terms" for information on usage and redistribution
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* of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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*
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* RCS: @(#) $Id: tclpreserve.c,v 1.1.1.1 2001/06/13 04:45:15 dtashley Exp $
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*/
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#include "tclInt.h"
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/*
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* The following data structure is used to keep track of all the
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* Tcl_Preserve calls that are still in effect. It grows as needed
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* to accommodate any number of calls in effect.
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*/
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typedef struct {
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ClientData clientData; /* Address of preserved block. */
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int refCount; /* Number of Tcl_Preserve calls in effect
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* for block. */
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int mustFree; /* Non-zero means Tcl_EventuallyFree was
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* called while a Tcl_Preserve call was in
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* effect, so the structure must be freed
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* when refCount becomes zero. */
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Tcl_FreeProc *freeProc; /* Procedure to call to free. */
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} Reference;
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static Reference *refArray; /* First in array of references. */
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static int spaceAvl = 0; /* Total number of structures available
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* at *firstRefPtr. */
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static int inUse = 0; /* Count of structures currently in use
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* in refArray. */
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#define INITIAL_SIZE 2
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TCL_DECLARE_MUTEX(preserveMutex)/* To protect the above statics */
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/*
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* The following data structure is used to keep track of whether an
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* arbitrary block of memory has been deleted. This is used by the
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* TclHandle code to avoid the more time-expensive algorithm of
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* Tcl_Preserve(). This mechanism is mainly used when we have lots of
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* references to a few big, expensive objects that we don't want to live
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* any longer than necessary.
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*/
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typedef struct HandleStruct {
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VOID *ptr; /* Pointer to the memory block being
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* tracked. This field will become NULL when
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* the memory block is deleted. This field
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* must be the first in the structure. */
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#ifdef TCL_MEM_DEBUG
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VOID *ptr2; /* Backup copy of the abpve pointer used to
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* ensure that the contents of the handle are
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* not changed by anyone else. */
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#endif
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int refCount; /* Number of TclHandlePreserve() calls in
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* effect on this handle. */
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} HandleStruct;
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/*
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* Static routines in this file:
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*/
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static void PreserveExitProc _ANSI_ARGS_((ClientData clientData));
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/*
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*----------------------------------------------------------------------
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*
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* PreserveExitProc --
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*
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* Called during exit processing to clean up the reference array.
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*
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* Results:
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* None.
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*
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* Side effects:
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* Frees the storage of the reference array.
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*
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*----------------------------------------------------------------------
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*/
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/* ARGSUSED */
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static void
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PreserveExitProc(clientData)
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ClientData clientData; /* NULL -Unused. */
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{
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Tcl_MutexLock(&preserveMutex);
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if (spaceAvl != 0) {
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ckfree((char *) refArray);
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refArray = (Reference *) NULL;
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inUse = 0;
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spaceAvl = 0;
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}
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Tcl_MutexUnlock(&preserveMutex);
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}
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/*
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*----------------------------------------------------------------------
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*
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* Tcl_Preserve --
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*
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* This procedure is used by a procedure to declare its interest
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* in a particular block of memory, so that the block will not be
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* reallocated until a matching call to Tcl_Release has been made.
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*
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* Results:
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* None.
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*
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* Side effects:
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* Information is retained so that the block of memory will
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* not be freed until at least the matching call to Tcl_Release.
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*
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*----------------------------------------------------------------------
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*/
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void
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Tcl_Preserve(clientData)
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ClientData clientData; /* Pointer to malloc'ed block of memory. */
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{
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Reference *refPtr;
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int i;
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/*
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* See if there is already a reference for this pointer. If so,
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* just increment its reference count.
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*/
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Tcl_MutexLock(&preserveMutex);
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for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) {
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if (refPtr->clientData == clientData) {
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refPtr->refCount++;
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Tcl_MutexUnlock(&preserveMutex);
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return;
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}
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}
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/*
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* Make a reference array if it doesn't already exist, or make it
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* bigger if it is full.
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*/
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if (inUse == spaceAvl) {
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if (spaceAvl == 0) {
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Tcl_CreateExitHandler((Tcl_ExitProc *) PreserveExitProc,
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(ClientData) NULL);
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refArray = (Reference *) ckalloc((unsigned)
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(INITIAL_SIZE*sizeof(Reference)));
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spaceAvl = INITIAL_SIZE;
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} else {
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Reference *new;
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new = (Reference *) ckalloc((unsigned)
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(2*spaceAvl*sizeof(Reference)));
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memcpy((VOID *) new, (VOID *) refArray,
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spaceAvl*sizeof(Reference));
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ckfree((char *) refArray);
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refArray = new;
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spaceAvl *= 2;
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}
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}
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/*
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* Make a new entry for the new reference.
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*/
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refPtr = &refArray[inUse];
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refPtr->clientData = clientData;
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refPtr->refCount = 1;
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refPtr->mustFree = 0;
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refPtr->freeProc = TCL_STATIC;
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inUse += 1;
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Tcl_MutexUnlock(&preserveMutex);
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}
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/*
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*----------------------------------------------------------------------
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*
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* Tcl_Release --
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*
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* This procedure is called to cancel a previous call to
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* Tcl_Preserve, thereby allowing a block of memory to be
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* freed (if no one else cares about it).
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*
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* Results:
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* None.
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*
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* Side effects:
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* If Tcl_EventuallyFree has been called for clientData, and if
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* no other call to Tcl_Preserve is still in effect, the block of
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* memory is freed.
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*
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*----------------------------------------------------------------------
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*/
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void
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Tcl_Release(clientData)
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ClientData clientData; /* Pointer to malloc'ed block of memory. */
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{
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Reference *refPtr;
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int mustFree;
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Tcl_FreeProc *freeProc;
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int i;
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Tcl_MutexLock(&preserveMutex);
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for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) {
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if (refPtr->clientData != clientData) {
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continue;
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}
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refPtr->refCount--;
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if (refPtr->refCount == 0) {
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/*
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* Must remove information from the slot before calling freeProc
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* to avoid reentrancy problems if the freeProc calls Tcl_Preserve
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* on the same clientData. Copy down the last reference in the
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* array to overwrite the current slot.
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*/
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freeProc = refPtr->freeProc;
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mustFree = refPtr->mustFree;
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inUse--;
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if (i < inUse) {
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refArray[i] = refArray[inUse];
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}
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if (mustFree) {
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if ((freeProc == TCL_DYNAMIC) ||
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(freeProc == (Tcl_FreeProc *) free)) {
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ckfree((char *) clientData);
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} else {
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Tcl_MutexUnlock(&preserveMutex);
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(*freeProc)((char *) clientData);
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return;
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}
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}
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}
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Tcl_MutexUnlock(&preserveMutex);
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return;
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}
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Tcl_MutexUnlock(&preserveMutex);
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/*
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* Reference not found. This is a bug in the caller.
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*/
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panic("Tcl_Release couldn't find reference for 0x%x", clientData);
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}
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/*
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*----------------------------------------------------------------------
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*
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* Tcl_EventuallyFree --
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*
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* Free up a block of memory, unless a call to Tcl_Preserve is in
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* effect for that block. In this case, defer the free until all
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* calls to Tcl_Preserve have been undone by matching calls to
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* Tcl_Release.
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*
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* Results:
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* None.
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*
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* Side effects:
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* Ptr may be released by calling free().
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274 |
*
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*----------------------------------------------------------------------
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*/
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void
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Tcl_EventuallyFree(clientData, freeProc)
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ClientData clientData; /* Pointer to malloc'ed block of memory. */
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Tcl_FreeProc *freeProc; /* Procedure to actually do free. */
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{
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283 |
Reference *refPtr;
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int i;
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285 |
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/*
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287 |
* See if there is a reference for this pointer. If so, set its
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* "mustFree" flag (the flag had better not be set already!).
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*/
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290 |
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Tcl_MutexLock(&preserveMutex);
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for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) {
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if (refPtr->clientData != clientData) {
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continue;
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}
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296 |
if (refPtr->mustFree) {
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297 |
panic("Tcl_EventuallyFree called twice for 0x%x\n", clientData);
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}
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refPtr->mustFree = 1;
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300 |
refPtr->freeProc = freeProc;
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301 |
Tcl_MutexUnlock(&preserveMutex);
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302 |
return;
|
303 |
}
|
304 |
Tcl_MutexUnlock(&preserveMutex);
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305 |
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306 |
/*
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307 |
* No reference for this block. Free it now.
|
308 |
*/
|
309 |
|
310 |
if ((freeProc == TCL_DYNAMIC)
|
311 |
|| (freeProc == (Tcl_FreeProc *) free)) {
|
312 |
ckfree((char *) clientData);
|
313 |
} else {
|
314 |
(*freeProc)((char *)clientData);
|
315 |
}
|
316 |
}
|
317 |
|
318 |
/*
|
319 |
*---------------------------------------------------------------------------
|
320 |
*
|
321 |
* TclHandleCreate --
|
322 |
*
|
323 |
* Allocate a handle that contains enough information to determine
|
324 |
* if an arbitrary malloc'd block has been deleted. This is
|
325 |
* used to avoid the more time-expensive algorithm of Tcl_Preserve().
|
326 |
*
|
327 |
* Results:
|
328 |
* The return value is a TclHandle that refers to the given malloc'd
|
329 |
* block. Doubly dereferencing the returned handle will give
|
330 |
* back the pointer to the block, or will give NULL if the block has
|
331 |
* been deleted.
|
332 |
*
|
333 |
* Side effects:
|
334 |
* The caller must keep track of this handle (generally by storing
|
335 |
* it in a field in the malloc'd block) and call TclHandleFree()
|
336 |
* on this handle when the block is deleted. Everything else that
|
337 |
* wishes to keep track of whether the malloc'd block has been deleted
|
338 |
* should use calls to TclHandlePreserve() and TclHandleRelease()
|
339 |
* on the associated handle.
|
340 |
*
|
341 |
*---------------------------------------------------------------------------
|
342 |
*/
|
343 |
|
344 |
TclHandle
|
345 |
TclHandleCreate(ptr)
|
346 |
VOID *ptr; /* Pointer to an arbitrary block of memory
|
347 |
* to be tracked for deletion. Must not be
|
348 |
* NULL. */
|
349 |
{
|
350 |
HandleStruct *handlePtr;
|
351 |
|
352 |
handlePtr = (HandleStruct *) ckalloc(sizeof(HandleStruct));
|
353 |
handlePtr->ptr = ptr;
|
354 |
#ifdef TCL_MEM_DEBUG
|
355 |
handlePtr->ptr2 = ptr;
|
356 |
#endif
|
357 |
handlePtr->refCount = 0;
|
358 |
return (TclHandle) handlePtr;
|
359 |
}
|
360 |
|
361 |
/*
|
362 |
*---------------------------------------------------------------------------
|
363 |
*
|
364 |
* TclHandleFree --
|
365 |
*
|
366 |
* Called when the arbitrary malloc'd block associated with the
|
367 |
* handle is being deleted. Modifies the handle so that doubly
|
368 |
* dereferencing it will give NULL. This informs any user of the
|
369 |
* handle that the block of memory formerly referenced by the
|
370 |
* handle has been freed.
|
371 |
*
|
372 |
* Results:
|
373 |
* None.
|
374 |
*
|
375 |
* Side effects:
|
376 |
* If nothing is referring to the handle, the handle will be reclaimed.
|
377 |
*
|
378 |
*---------------------------------------------------------------------------
|
379 |
*/
|
380 |
|
381 |
void
|
382 |
TclHandleFree(handle)
|
383 |
TclHandle handle; /* Previously created handle associated
|
384 |
* with a malloc'd block that is being
|
385 |
* deleted. The handle is modified so that
|
386 |
* doubly dereferencing it will give NULL. */
|
387 |
{
|
388 |
HandleStruct *handlePtr;
|
389 |
|
390 |
handlePtr = (HandleStruct *) handle;
|
391 |
#ifdef TCL_MEM_DEBUG
|
392 |
if (handlePtr->refCount == 0x61616161) {
|
393 |
panic("using previously disposed TclHandle %x", handlePtr);
|
394 |
}
|
395 |
if (handlePtr->ptr2 != handlePtr->ptr) {
|
396 |
panic("someone has changed the block referenced by the handle %x\nfrom %x to %x",
|
397 |
handlePtr, handlePtr->ptr2, handlePtr->ptr);
|
398 |
}
|
399 |
#endif
|
400 |
handlePtr->ptr = NULL;
|
401 |
if (handlePtr->refCount == 0) {
|
402 |
ckfree((char *) handlePtr);
|
403 |
}
|
404 |
}
|
405 |
|
406 |
/*
|
407 |
*---------------------------------------------------------------------------
|
408 |
*
|
409 |
* TclHandlePreserve --
|
410 |
*
|
411 |
* Declare an interest in the arbitrary malloc'd block associated
|
412 |
* with the handle.
|
413 |
*
|
414 |
* Results:
|
415 |
* The return value is the handle argument, with its ref count
|
416 |
* incremented.
|
417 |
*
|
418 |
* Side effects:
|
419 |
* For each call to TclHandlePreserve(), there should be a matching
|
420 |
* call to TclHandleRelease() when the caller is no longer interested
|
421 |
* in the malloc'd block associated with the handle.
|
422 |
*
|
423 |
*---------------------------------------------------------------------------
|
424 |
*/
|
425 |
|
426 |
TclHandle
|
427 |
TclHandlePreserve(handle)
|
428 |
TclHandle handle; /* Declare an interest in the block of
|
429 |
* memory referenced by this handle. */
|
430 |
{
|
431 |
HandleStruct *handlePtr;
|
432 |
|
433 |
handlePtr = (HandleStruct *) handle;
|
434 |
#ifdef TCL_MEM_DEBUG
|
435 |
if (handlePtr->refCount == 0x61616161) {
|
436 |
panic("using previously disposed TclHandle %x", handlePtr);
|
437 |
}
|
438 |
if ((handlePtr->ptr != NULL)
|
439 |
&& (handlePtr->ptr != handlePtr->ptr2)) {
|
440 |
panic("someone has changed the block referenced by the handle %x\nfrom %x to %x",
|
441 |
handlePtr, handlePtr->ptr2, handlePtr->ptr);
|
442 |
}
|
443 |
#endif
|
444 |
handlePtr->refCount++;
|
445 |
|
446 |
return handle;
|
447 |
}
|
448 |
|
449 |
/*
|
450 |
*---------------------------------------------------------------------------
|
451 |
*
|
452 |
* TclHandleRelease --
|
453 |
*
|
454 |
* This procedure is called to release an interest in the malloc'd
|
455 |
* block associated with the handle.
|
456 |
*
|
457 |
* Results:
|
458 |
* None.
|
459 |
*
|
460 |
* Side effects:
|
461 |
* The ref count of the handle is decremented. If the malloc'd block
|
462 |
* has been freed and if no one is using the handle any more, the
|
463 |
* handle will be reclaimed.
|
464 |
*
|
465 |
*---------------------------------------------------------------------------
|
466 |
*/
|
467 |
|
468 |
void
|
469 |
TclHandleRelease(handle)
|
470 |
TclHandle handle; /* Unregister interest in the block of
|
471 |
* memory referenced by this handle. */
|
472 |
{
|
473 |
HandleStruct *handlePtr;
|
474 |
|
475 |
handlePtr = (HandleStruct *) handle;
|
476 |
#ifdef TCL_MEM_DEBUG
|
477 |
if (handlePtr->refCount == 0x61616161) {
|
478 |
panic("using previously disposed TclHandle %x", handlePtr);
|
479 |
}
|
480 |
if ((handlePtr->ptr != NULL)
|
481 |
&& (handlePtr->ptr != handlePtr->ptr2)) {
|
482 |
panic("someone has changed the block referenced by the handle %x\nfrom %x to %x",
|
483 |
handlePtr, handlePtr->ptr2, handlePtr->ptr);
|
484 |
}
|
485 |
#endif
|
486 |
handlePtr->refCount--;
|
487 |
if ((handlePtr->refCount == 0) && (handlePtr->ptr == NULL)) {
|
488 |
ckfree((char *) handlePtr);
|
489 |
}
|
490 |
}
|
491 |
|
492 |
/* End of tclpreserve.c */
|