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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