git.zerfleddert.de Git - micropolis/blob - src/tk/tkpresrv.c

   1 /*
   2  * tkPreserve.c --
   3  *
   4  *      This file contains a collection of procedures that are used
   5  *      to make sure that widget records and other data structures
   6  *      aren't reallocated when there are nested procedures that
   7  *      depend on their existence.
   8  *
   9  * Copyright 1991 Regents of the University of California
  10  * Permission to use, copy, modify, and distribute this
  11  * software and its documentation for any purpose and without
  12  * fee is hereby granted, provided that this copyright
  13  * notice appears in all copies.  The University of California
  14  * makes no representations about the suitability of this
  15  * software for any purpose.  It is provided "as is" without
  16  * express or implied warranty.
  17  */
  18
  19 #ifndef lint
  20 static char rcsid[] = "$Header: /user6/ouster/wish/RCS/tkPreserve.c,v 1.6 92/06/15 13:44:51 ouster Exp $ SPRITE (Berkeley)";
  21 #endif /* not lint */
  22
  23 #include "tkconfig.h"
  24 #include "tk.h"
  25
  26 /*
  27  * The following data structure is used to keep track of all the
  28  * Tk_Preserve calls that are still in effect.  It grows as needed
  29  * to accommodate any number of calls in effect.
  30  */
  31
  32 typedef struct {
  33     ClientData clientData;      /* Address of preserved block. */
  34     int refCount;               /* Number of Tk_Preserve calls in effect
  35                                  * for block. */
  36     int mustFree;               /* Non-zero means Tk_EventuallyFree was
  37                                  * called while a Tk_Preserve call was in
  38                                  * effect, so the structure must be freed
  39                                  * when refCount becomes zero. */
  40     Tk_FreeProc *freeProc;      /* Procedure to call to free. */
  41 } Reference;
  42
  43 static Reference *refArray;     /* First in array of references. */
  44 static int spaceAvl = 0;        /* Total number of structures available
  45                                  * at *firstRefPtr. */
  46 static int inUse = 0;           /* Count of structures currently in use
  47                                  * in refArray. */
  48 #define INITIAL_SIZE 2
  49 \f
  50 /*
  51  *----------------------------------------------------------------------
  52  *
  53  * Tk_Preserve --
  54  *
  55  *      This procedure is used by a procedure to declare its interest
  56  *      in a particular block of memory, so that the block will not be
  57  *      reallocated until a matching call to Tk_Release has been made.
  58  *
  59  * Results:
  60  *      None.
  61  *
  62  * Side effects:
  63  *      Information is retained so that the block of memory will
  64  *      not be freed until at least the matching call to Tk_Release.
  65  *
  66  *----------------------------------------------------------------------
  67  */
  68
  69 void
  70 Tk_Preserve(clientData)
  71     ClientData clientData;      /* Pointer to malloc'ed block of memory. */
  72 {
  73     register Reference *refPtr;
  74     int i;
  75
  76     /*
  77      * See if there is already a reference for this pointer.  If so,
  78      * just increment its reference count.
  79      */
  80
  81     for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) {
  82         if (refPtr->clientData == clientData) {
  83             refPtr->refCount++;
  84             return;
  85         }
  86     }
  87
  88     /*
  89      * Make a reference array if it doesn't already exist, or make it
  90      * bigger if it is full.
  91      */
  92
  93     if (inUse == spaceAvl) {
  94         if (spaceAvl == 0) {
  95             refArray = (Reference *) ckalloc((unsigned)
  96                     (INITIAL_SIZE*sizeof(Reference)));
  97             spaceAvl = INITIAL_SIZE;
  98         } else {
  99             Reference *new;
 100
 101             new = (Reference *) ckalloc((unsigned)
 102                     (2*spaceAvl*sizeof(Reference)));
 103             memcpy((VOID *) new, (VOID *) refArray, spaceAvl*sizeof(Reference));
 104             ckfree((char *) refArray);
 105             refArray = new;
 106             spaceAvl *= 2;
 107         }
 108     }
 109
 110     /*
 111      * Make a new entry for the new reference.
 112      */
 113
 114     refPtr = &refArray[inUse];
 115     refPtr->clientData = clientData;
 116     refPtr->refCount = 1;
 117     refPtr->mustFree = 0;
 118     inUse += 1;
 119 }
 120 \f
 121 /*
 122  *----------------------------------------------------------------------
 123  *
 124  * Tk_Release --
 125  *
 126  *      This procedure is called to cancel a previous call to
 127  *      Tk_Preserve, thereby allowing a block of memory to be
 128  *      freed (if no one else cares about it).
 129  *
 130  * Results:
 131  *      None.
 132  *
 133  * Side effects:
 134  *      If Tk_EventuallyFree has been called for clientData, and if
 135  *      no other call to Tk_Preserve is still in effect, the block of
 136  *      memory is freed.
 137  *
 138  *----------------------------------------------------------------------
 139  */
 140
 141 void
 142 Tk_Release(clientData)
 143     ClientData clientData;      /* Pointer to malloc'ed block of memory. */
 144 {
 145     register Reference *refPtr;
 146     int i;
 147
 148     for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) {
 149         if (refPtr->clientData != clientData) {
 150             continue;
 151         }
 152         refPtr->refCount--;
 153         if (refPtr->refCount == 0) {
 154             if (refPtr->mustFree) {
 155                 if (refPtr->freeProc == (Tk_FreeProc *) free) {
 156                     ckfree((char *) refPtr->clientData);
 157                 } else {
 158                     (*refPtr->freeProc)(refPtr->clientData);
 159                 }
 160             }
 161
 162             /*
 163              * Copy down all of the trailing reference in the array
 164              * to cover up the hole left by the unused reference.
 165              */
 166
 167             inUse--;
 168             if (i != inUse) {
 169                 memcpy((VOID *) &refArray[i], (VOID *) &refArray[i+1],
 170                         (inUse-i)*sizeof(Reference));
 171             }
 172         }
 173         return;
 174     }
 175
 176     /*
 177      * Reference not found.  This is a bug in the caller.
 178      */
 179
 180     panic("Tk_Release couldn't find reference for 0x%x", clientData);
 181 }
 182 \f
 183 /*
 184  *----------------------------------------------------------------------
 185  *
 186  * Tk_EventuallyFree --
 187  *
 188  *      Free up a block of memory, unless a call to Tk_Preserve is in
 189  *      effect for that block.  In this case, defer the free until all
 190  *      calls to Tk_Preserve have been undone by matching calls to
 191  *      Tk_Release.
 192  *
 193  * Results:
 194  *      None.
 195  *
 196  * Side effects:
 197  *      Ptr may be released by calling free().
 198  *
 199  *----------------------------------------------------------------------
 200  */
 201
 202 void
 203 Tk_EventuallyFree(clientData, freeProc)
 204     ClientData clientData;      /* Pointer to malloc'ed block of memory. */
 205     Tk_FreeProc *freeProc;      /* Procedure to actually do free. */
 206 {
 207     register Reference *refPtr;
 208     int i;
 209
 210     /*
 211      * See if there is a reference for this pointer.  If so, set its
 212      * "mustFree" flag (the flag had better not be set already!).
 213      */
 214
 215     for (i = 0, refPtr = refArray; i < inUse; i++, refPtr++) {
 216         if (refPtr->clientData != clientData) {
 217             continue;
 218         }
 219         if (refPtr->mustFree) {
 220             panic("Tk_EventuallyFree called twice for 0x%x\n", clientData);
 221         }
 222         refPtr->mustFree = 1;
 223         refPtr->freeProc = freeProc;
 224         return;
 225     }
 226
 227     /*
 228      * No reference for this block.  Free it now.
 229      */
 230
 231     if (freeProc == (Tk_FreeProc *) free) {
 232         ckfree((char *) clientData);
 233     } else {
 234         (*freeProc)(clientData);
 235     }
 236 }