[25] | 1 | /* |
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| 2 | * tclPreserve.c -- |
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| 3 | * |
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| 4 | * This file contains a collection of functions that are used to make |
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| 5 | * sure that widget records and other data structures aren't reallocated |
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| 6 | * when there are nested functions that depend on their existence. |
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| 7 | * |
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| 8 | * Copyright (c) 1991-1994 The Regents of the University of California. |
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| 9 | * Copyright (c) 1994-1998 Sun Microsystems, Inc. |
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| 10 | * |
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| 11 | * See the file "license.terms" for information on usage and redistribution of |
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| 12 | * this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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| 13 | * |
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| 14 | * RCS: @(#) $Id: tclPreserve.c,v 1.10 2007/03/21 18:02:51 dgp Exp $ |
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| 15 | */ |
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| 16 | |
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| 17 | #include "tclInt.h" |
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| 18 | |
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| 19 | /* |
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| 20 | * The following data structure is used to keep track of all the Tcl_Preserve |
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| 21 | * calls that are still in effect. It grows as needed to accommodate any |
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| 22 | * number of calls in effect. |
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| 23 | */ |
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| 24 | |
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| 25 | typedef struct { |
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| 26 | ClientData clientData; /* Address of preserved block. */ |
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| 27 | int refCount; /* Number of Tcl_Preserve calls in effect for |
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| 28 | * block. */ |
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| 29 | int mustFree; /* Non-zero means Tcl_EventuallyFree was |
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| 30 | * called while a Tcl_Preserve call was in |
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| 31 | * effect, so the structure must be freed when |
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| 32 | * refCount becomes zero. */ |
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| 33 | Tcl_FreeProc *freeProc; /* Function to call to free. */ |
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| 34 | } Reference; |
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| 35 | |
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| 36 | /* |
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| 37 | * Global data structures used to hold the list of preserved data references. |
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| 38 | * These variables are protected by "preserveMutex". |
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| 39 | */ |
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| 40 | |
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| 41 | static Reference *refArray = NULL; /* First in array of references. */ |
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| 42 | static int spaceAvl = 0; /* Total number of structures available at |
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| 43 | * *firstRefPtr. */ |
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| 44 | static int inUse = 0; /* Count of structures currently in use in |
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| 45 | * refArray. */ |
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| 46 | TCL_DECLARE_MUTEX(preserveMutex)/* To protect the above statics */ |
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| 47 | |
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| 48 | #define INITIAL_SIZE 2 /* Initial number of reference slots to make */ |
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| 49 | |
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| 50 | /* |
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| 51 | * The following data structure is used to keep track of whether an arbitrary |
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| 52 | * block of memory has been deleted. This is used by the TclHandle code to |
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| 53 | * avoid the more time-expensive algorithm of Tcl_Preserve(). This mechanism |
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| 54 | * is mainly used when we have lots of references to a few big, expensive |
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| 55 | * objects that we don't want to live any longer than necessary. |
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| 56 | */ |
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| 57 | |
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| 58 | typedef struct HandleStruct { |
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| 59 | void *ptr; /* Pointer to the memory block being tracked. |
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| 60 | * This field will become NULL when the memory |
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| 61 | * block is deleted. This field must be the |
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| 62 | * first in the structure. */ |
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| 63 | #ifdef TCL_MEM_DEBUG |
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| 64 | void *ptr2; /* Backup copy of the above pointer used to |
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| 65 | * ensure that the contents of the handle are |
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| 66 | * not changed by anyone else. */ |
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| 67 | #endif |
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| 68 | int refCount; /* Number of TclHandlePreserve() calls in |
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| 69 | * effect on this handle. */ |
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| 70 | } HandleStruct; |
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| 71 | |
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| 72 | /* |
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| 73 | *---------------------------------------------------------------------- |
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| 74 | * |
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| 75 | * TclFinalizePreserve -- |
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| 76 | * |
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| 77 | * Called during exit processing to clean up the reference array. |
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| 78 | * |
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| 79 | * Results: |
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| 80 | * None. |
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| 81 | * |
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| 82 | * Side effects: |
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| 83 | * Frees the storage of the reference array. |
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| 84 | * |
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| 85 | *---------------------------------------------------------------------- |
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| 86 | */ |
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| 87 | |
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| 88 | /* ARGSUSED */ |
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| 89 | void |
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| 90 | TclFinalizePreserve(void) |
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| 91 | { |
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| 92 | Tcl_MutexLock(&preserveMutex); |
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| 93 | if (spaceAvl != 0) { |
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| 94 | ckfree((char *) refArray); |
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| 95 | refArray = NULL; |
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| 96 | inUse = 0; |
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| 97 | spaceAvl = 0; |
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| 98 | } |
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| 99 | Tcl_MutexUnlock(&preserveMutex); |
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| 100 | } |
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| 101 | |
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| 102 | /* |
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| 103 | *---------------------------------------------------------------------- |
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| 104 | * |
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| 105 | * Tcl_Preserve -- |
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| 106 | * |
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| 107 | * This function is used by a function to declare its interest in a |
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| 108 | * particular block of memory, so that the block will not be reallocated |
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| 109 | * until a matching call to Tcl_Release has been made. |
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| 110 | * |
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| 111 | * Results: |
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| 112 | * None. |
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| 113 | * |
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| 114 | * Side effects: |
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| 115 | * Information is retained so that the block of memory will not be freed |
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| 116 | * until at least the matching call to Tcl_Release. |
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| 117 | * |
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| 118 | *---------------------------------------------------------------------- |
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| 119 | */ |
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| 120 | |
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| 121 | void |
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| 122 | Tcl_Preserve( |
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| 123 | ClientData clientData) /* Pointer to malloc'ed block of memory. */ |
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| 124 | { |
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| 125 | Reference *refPtr; |
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| 126 | int i; |
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| 127 | |
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| 128 | /* |
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| 129 | * See if there is already a reference for this pointer. If so, just |
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| 130 | * increment its reference count. |
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| 131 | */ |
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| 132 | |
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| 133 | Tcl_MutexLock(&preserveMutex); |
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| 134 | for (i=0, refPtr=refArray ; i<inUse ; i++, refPtr++) { |
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| 135 | if (refPtr->clientData == clientData) { |
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| 136 | refPtr->refCount++; |
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| 137 | Tcl_MutexUnlock(&preserveMutex); |
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| 138 | return; |
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| 139 | } |
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| 140 | } |
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| 141 | |
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| 142 | /* |
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| 143 | * Make a reference array if it doesn't already exist, or make it bigger |
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| 144 | * if it is full. |
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| 145 | */ |
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| 146 | |
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| 147 | if (inUse == spaceAvl) { |
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| 148 | spaceAvl = spaceAvl ? 2*spaceAvl : INITIAL_SIZE; |
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| 149 | refArray = (Reference *) ckrealloc((char *) refArray, |
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| 150 | spaceAvl * sizeof(Reference)); |
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| 151 | } |
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| 152 | |
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| 153 | /* |
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| 154 | * Make a new entry for the new reference. |
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| 155 | */ |
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| 156 | |
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| 157 | refPtr = &refArray[inUse]; |
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| 158 | refPtr->clientData = clientData; |
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| 159 | refPtr->refCount = 1; |
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| 160 | refPtr->mustFree = 0; |
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| 161 | refPtr->freeProc = TCL_STATIC; |
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| 162 | inUse += 1; |
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| 163 | Tcl_MutexUnlock(&preserveMutex); |
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| 164 | } |
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| 165 | |
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| 166 | /* |
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| 167 | *---------------------------------------------------------------------- |
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| 168 | * |
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| 169 | * Tcl_Release -- |
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| 170 | * |
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| 171 | * This function is called to cancel a previous call to Tcl_Preserve, |
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| 172 | * thereby allowing a block of memory to be freed (if no one else cares |
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| 173 | * about it). |
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| 174 | * |
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| 175 | * Results: |
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| 176 | * None. |
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| 177 | * |
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| 178 | * Side effects: |
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| 179 | * If Tcl_EventuallyFree has been called for clientData, and if no other |
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| 180 | * call to Tcl_Preserve is still in effect, the block of memory is freed. |
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| 181 | * |
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| 182 | *---------------------------------------------------------------------- |
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| 183 | */ |
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| 184 | |
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| 185 | void |
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| 186 | Tcl_Release( |
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| 187 | ClientData clientData) /* Pointer to malloc'ed block of memory. */ |
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| 188 | { |
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| 189 | Reference *refPtr; |
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| 190 | int i; |
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| 191 | |
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| 192 | Tcl_MutexLock(&preserveMutex); |
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| 193 | for (i=0, refPtr=refArray ; i<inUse ; i++, refPtr++) { |
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| 194 | int mustFree; |
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| 195 | Tcl_FreeProc *freeProc; |
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| 196 | |
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| 197 | if (refPtr->clientData != clientData) { |
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| 198 | continue; |
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| 199 | } |
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| 200 | |
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| 201 | if (--refPtr->refCount != 0) { |
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| 202 | Tcl_MutexUnlock(&preserveMutex); |
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| 203 | return; |
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| 204 | } |
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| 205 | |
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| 206 | /* |
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| 207 | * Must remove information from the slot before calling freeProc to |
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| 208 | * avoid reentrancy problems if the freeProc calls Tcl_Preserve on the |
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| 209 | * same clientData. Copy down the last reference in the array to |
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| 210 | * overwrite the current slot. |
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| 211 | */ |
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| 212 | |
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| 213 | freeProc = refPtr->freeProc; |
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| 214 | mustFree = refPtr->mustFree; |
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| 215 | inUse--; |
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| 216 | if (i < inUse) { |
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| 217 | refArray[i] = refArray[inUse]; |
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| 218 | } |
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| 219 | |
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| 220 | /* |
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| 221 | * Now committed to disposing the data. But first, we've patched up |
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| 222 | * all the global data structures so we should release the mutex now. |
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| 223 | * Only then should we dabble around with potentially-slow memory |
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| 224 | * managers... |
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| 225 | */ |
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| 226 | |
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| 227 | Tcl_MutexUnlock(&preserveMutex); |
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| 228 | if (mustFree) { |
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| 229 | if (freeProc == TCL_DYNAMIC) { |
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| 230 | ckfree((char *) clientData); |
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| 231 | } else { |
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| 232 | (*freeProc)((char *) clientData); |
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| 233 | } |
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| 234 | } |
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| 235 | return; |
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| 236 | } |
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| 237 | Tcl_MutexUnlock(&preserveMutex); |
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| 238 | |
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| 239 | /* |
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| 240 | * Reference not found. This is a bug in the caller. |
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| 241 | */ |
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| 242 | |
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| 243 | Tcl_Panic("Tcl_Release couldn't find reference for 0x%x", clientData); |
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| 244 | } |
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| 245 | |
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| 246 | /* |
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| 247 | *---------------------------------------------------------------------- |
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| 248 | * |
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| 249 | * Tcl_EventuallyFree -- |
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| 250 | * |
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| 251 | * Free up a block of memory, unless a call to Tcl_Preserve is in effect |
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| 252 | * for that block. In this case, defer the free until all calls to |
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| 253 | * Tcl_Preserve have been undone by matching calls to Tcl_Release. |
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| 254 | * |
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| 255 | * Results: |
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| 256 | * None. |
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| 257 | * |
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| 258 | * Side effects: |
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| 259 | * Ptr may be released by calling free(). |
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| 260 | * |
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| 261 | *---------------------------------------------------------------------- |
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| 262 | */ |
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| 263 | |
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| 264 | void |
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| 265 | Tcl_EventuallyFree( |
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| 266 | ClientData clientData, /* Pointer to malloc'ed block of memory. */ |
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| 267 | Tcl_FreeProc *freeProc) /* Function to actually do free. */ |
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| 268 | { |
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| 269 | Reference *refPtr; |
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| 270 | int i; |
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| 271 | |
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| 272 | /* |
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| 273 | * See if there is a reference for this pointer. If so, set its "mustFree" |
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| 274 | * flag (the flag had better not be set already!). |
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| 275 | */ |
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| 276 | |
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| 277 | Tcl_MutexLock(&preserveMutex); |
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| 278 | for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) { |
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| 279 | if (refPtr->clientData != clientData) { |
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| 280 | continue; |
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| 281 | } |
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| 282 | if (refPtr->mustFree) { |
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| 283 | Tcl_Panic("Tcl_EventuallyFree called twice for 0x%x", |
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| 284 | clientData); |
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| 285 | } |
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| 286 | refPtr->mustFree = 1; |
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| 287 | refPtr->freeProc = freeProc; |
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| 288 | Tcl_MutexUnlock(&preserveMutex); |
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| 289 | return; |
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| 290 | } |
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| 291 | Tcl_MutexUnlock(&preserveMutex); |
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| 292 | |
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| 293 | /* |
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| 294 | * No reference for this block. Free it now. |
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| 295 | */ |
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| 296 | |
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| 297 | if (freeProc == TCL_DYNAMIC) { |
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| 298 | ckfree((char *) clientData); |
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| 299 | } else { |
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| 300 | (*freeProc)((char *)clientData); |
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| 301 | } |
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| 302 | } |
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| 303 | |
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| 304 | /* |
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| 305 | *--------------------------------------------------------------------------- |
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| 306 | * |
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| 307 | * TclHandleCreate -- |
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| 308 | * |
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| 309 | * Allocate a handle that contains enough information to determine if an |
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| 310 | * arbitrary malloc'd block has been deleted. This is used to avoid the |
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| 311 | * more time-expensive algorithm of Tcl_Preserve(). |
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| 312 | * |
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| 313 | * Results: |
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| 314 | * The return value is a TclHandle that refers to the given malloc'd |
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| 315 | * block. Doubly dereferencing the returned handle will give back the |
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| 316 | * pointer to the block, or will give NULL if the block has been deleted. |
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| 317 | * |
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| 318 | * Side effects: |
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| 319 | * The caller must keep track of this handle (generally by storing it in |
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| 320 | * a field in the malloc'd block) and call TclHandleFree() on this handle |
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| 321 | * when the block is deleted. Everything else that wishes to keep track |
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| 322 | * of whether the malloc'd block has been deleted should use calls to |
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| 323 | * TclHandlePreserve() and TclHandleRelease() on the associated handle. |
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| 324 | * |
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| 325 | *--------------------------------------------------------------------------- |
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| 326 | */ |
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| 327 | |
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| 328 | TclHandle |
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| 329 | TclHandleCreate( |
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| 330 | void *ptr) /* Pointer to an arbitrary block of memory to |
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| 331 | * be tracked for deletion. Must not be |
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| 332 | * NULL. */ |
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| 333 | { |
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| 334 | HandleStruct *handlePtr; |
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| 335 | |
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| 336 | handlePtr = (HandleStruct *) ckalloc(sizeof(HandleStruct)); |
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| 337 | handlePtr->ptr = ptr; |
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| 338 | #ifdef TCL_MEM_DEBUG |
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| 339 | handlePtr->ptr2 = ptr; |
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| 340 | #endif |
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| 341 | handlePtr->refCount = 0; |
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| 342 | return (TclHandle) handlePtr; |
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| 343 | } |
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| 344 | |
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| 345 | /* |
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| 346 | *--------------------------------------------------------------------------- |
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| 347 | * |
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| 348 | * TclHandleFree -- |
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| 349 | * |
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| 350 | * Called when the arbitrary malloc'd block associated with the handle is |
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| 351 | * being deleted. Modifies the handle so that doubly dereferencing it |
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| 352 | * will give NULL. This informs any user of the handle that the block of |
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| 353 | * memory formerly referenced by the handle has been freed. |
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| 354 | * |
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| 355 | * Results: |
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| 356 | * None. |
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| 357 | * |
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| 358 | * Side effects: |
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| 359 | * If nothing is referring to the handle, the handle will be reclaimed. |
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| 360 | * |
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| 361 | *--------------------------------------------------------------------------- |
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| 362 | */ |
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| 363 | |
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| 364 | void |
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| 365 | TclHandleFree( |
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| 366 | TclHandle handle) /* Previously created handle associated with a |
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| 367 | * malloc'd block that is being deleted. The |
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| 368 | * handle is modified so that doubly |
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| 369 | * dereferencing it will give NULL. */ |
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| 370 | { |
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| 371 | HandleStruct *handlePtr; |
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| 372 | |
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| 373 | handlePtr = (HandleStruct *) handle; |
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| 374 | #ifdef TCL_MEM_DEBUG |
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| 375 | if (handlePtr->refCount == 0x61616161) { |
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| 376 | Tcl_Panic("using previously disposed TclHandle %x", handlePtr); |
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| 377 | } |
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| 378 | if (handlePtr->ptr2 != handlePtr->ptr) { |
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| 379 | Tcl_Panic("someone has changed the block referenced by the handle %x\nfrom %x to %x", |
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| 380 | handlePtr, handlePtr->ptr2, handlePtr->ptr); |
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| 381 | } |
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| 382 | #endif |
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| 383 | handlePtr->ptr = NULL; |
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| 384 | if (handlePtr->refCount == 0) { |
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| 385 | ckfree((char *) handlePtr); |
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| 386 | } |
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| 387 | } |
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| 388 | |
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| 389 | /* |
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| 390 | *--------------------------------------------------------------------------- |
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| 391 | * |
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| 392 | * TclHandlePreserve -- |
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| 393 | * |
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| 394 | * Declare an interest in the arbitrary malloc'd block associated with |
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| 395 | * the handle. |
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| 396 | * |
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| 397 | * Results: |
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| 398 | * The return value is the handle argument, with its ref count |
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| 399 | * incremented. |
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| 400 | * |
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| 401 | * Side effects: |
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| 402 | * For each call to TclHandlePreserve(), there should be a matching call |
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| 403 | * to TclHandleRelease() when the caller is no longer interested in the |
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| 404 | * malloc'd block associated with the handle. |
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| 405 | * |
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| 406 | *--------------------------------------------------------------------------- |
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| 407 | */ |
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| 408 | |
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| 409 | TclHandle |
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| 410 | TclHandlePreserve( |
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| 411 | TclHandle handle) /* Declare an interest in the block of memory |
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| 412 | * referenced by this handle. */ |
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| 413 | { |
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| 414 | HandleStruct *handlePtr; |
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| 415 | |
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| 416 | handlePtr = (HandleStruct *) handle; |
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| 417 | #ifdef TCL_MEM_DEBUG |
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| 418 | if (handlePtr->refCount == 0x61616161) { |
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| 419 | Tcl_Panic("using previously disposed TclHandle %x", handlePtr); |
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| 420 | } |
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| 421 | if ((handlePtr->ptr != NULL) && (handlePtr->ptr != handlePtr->ptr2)) { |
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| 422 | Tcl_Panic("someone has changed the block referenced by the handle %x\nfrom %x to %x", |
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| 423 | handlePtr, handlePtr->ptr2, handlePtr->ptr); |
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| 424 | } |
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| 425 | #endif |
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| 426 | handlePtr->refCount++; |
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| 427 | |
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| 428 | return handle; |
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| 429 | } |
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| 430 | |
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| 431 | /* |
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| 432 | *--------------------------------------------------------------------------- |
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| 433 | * |
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| 434 | * TclHandleRelease -- |
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| 435 | * |
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| 436 | * This function is called to release an interest in the malloc'd block |
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| 437 | * associated with the handle. |
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| 438 | * |
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| 439 | * Results: |
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| 440 | * None. |
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| 441 | * |
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| 442 | * Side effects: |
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| 443 | * The ref count of the handle is decremented. If the malloc'd block has |
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| 444 | * been freed and if no one is using the handle any more, the handle will |
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| 445 | * be reclaimed. |
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| 446 | * |
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| 447 | *--------------------------------------------------------------------------- |
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| 448 | */ |
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| 449 | |
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| 450 | void |
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| 451 | TclHandleRelease( |
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| 452 | TclHandle handle) /* Unregister interest in the block of memory |
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| 453 | * referenced by this handle. */ |
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| 454 | { |
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| 455 | HandleStruct *handlePtr; |
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| 456 | |
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| 457 | handlePtr = (HandleStruct *) handle; |
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| 458 | #ifdef TCL_MEM_DEBUG |
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| 459 | if (handlePtr->refCount == 0x61616161) { |
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| 460 | Tcl_Panic("using previously disposed TclHandle %x", handlePtr); |
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| 461 | } |
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| 462 | if ((handlePtr->ptr != NULL) && (handlePtr->ptr != handlePtr->ptr2)) { |
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| 463 | Tcl_Panic("someone has changed the block referenced by the handle %x\nfrom %x to %x", |
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| 464 | handlePtr, handlePtr->ptr2, handlePtr->ptr); |
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| 465 | } |
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| 466 | #endif |
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| 467 | handlePtr->refCount--; |
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| 468 | if ((handlePtr->refCount == 0) && (handlePtr->ptr == NULL)) { |
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| 469 | ckfree((char *) handlePtr); |
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| 470 | } |
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| 471 | } |
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| 472 | |
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| 473 | /* |
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| 474 | * Local Variables: |
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| 475 | * mode: c |
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| 476 | * c-basic-offset: 4 |
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| 477 | * fill-column: 78 |
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| 478 | * End: |
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| 479 | */ |
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