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1 /* Simple 'n' stupid dynamic-array module.
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2 Copyright (C) 1993 Sun Microsystems, Inc.
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3
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4 This file is part of XEmacs.
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5
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6 XEmacs is free software; you can redistribute it and/or modify it
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7 under the terms of the GNU General Public License as published by the
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8 Free Software Foundation; either version 2, or (at your option) any
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9 later version.
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10
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11 XEmacs is distributed in the hope that it will be useful, but WITHOUT
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12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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14 for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with XEmacs; see the file COPYING. If not, write to
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18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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19 Boston, MA 02111-1307, USA. */
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20
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21 /* Synched up with: Not in FSF. */
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22
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23 /* Written by Ben Wing, December 1993. */
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24
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25 /*
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26
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27 A "dynamic array" is a contiguous array of fixed-size elements where there
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28 is no upper limit (except available memory) on the number of elements in the
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29 array. Because the elements are maintained contiguously, space is used
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30 efficiently (no per-element pointers necessary) and random access to a
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31 particular element is in constant time. At any one point, the block of memory
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32 that holds the array has an upper limit; if this limit is exceeded, the
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33 memory is realloc()ed into a new array that is twice as big. Assuming that
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34 the time to grow the array is on the order of the new size of the array
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35 block, this scheme has a provably constant amortized time (i.e. average
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36 time over all additions).
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37
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38 When you add elements or retrieve elements, pointers are used. Note that
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39 the element itself (of whatever size it is), and not the pointer to it,
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40 is stored in the array; thus you do not have to allocate any heap memory
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41 on your own. Also, returned pointers are only guaranteed to be valid
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42 until the next operation that changes the length of the array.
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43
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44 This is a container object. Declare a dynamic array of a specific type
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45 as follows:
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46
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47 struct mytype_dynarr
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48 {
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49 Dynarr_declare (mytype);
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50 };
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51
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52 Use the following functions/macros:
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53
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54 void *Dynarr_new(type)
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55 [MACRO] Create a new dynamic-array object, with each element of the
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56 specified type. The return value is a void * and must be cast to the
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57 proper dynamic array type.
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58
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59 Dynarr_add(d, el)
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60 [MACRO] Add an element to the end of a dynamic array. EL is a pointer
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61 to the element; the element itself is stored in the array, however.
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62 No function call is performed unless the array needs to be resized.
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63
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64 Dynarr_add_many(d, base, len)
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65 [MACRO] Add LEN elements to the end of the dynamic array. The elements
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66 should be contiguous in memory, starting at BASE.
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67
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68 Dynarr_insert_many_at_start(d, base, len)
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69 [MACRO] Append LEN elements to the beginning of the dynamic array.
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70 The elements should be contiguous in memory, starting at BASE.
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71
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72 Dynarr_insert_many(d, base, len, start)
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73 Insert LEN elements to the dynamic arrary starting at position
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74 START. The elements should be contiguous in memory, starting at BASE.
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75
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76 int Dynarr_length(d)
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77 [MACRO] Return the number of elements currently in a dynamic array.
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78
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79 type Dynarr_at(d, i)
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80 [MACRO] Return the element at the specified index (no bounds checking
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81 done on the index). The element itself is returned, not a pointer
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82 to it.
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83
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84 type *Dynarr_atp(d, i)
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85 [MACRO] Return a pointer to the element at the specified index (no
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86 bounds checking done on the index). The pointer may not be valid
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87 after an element is added to or removed from the array.
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88
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89 Dynarr_reset(d)
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90 [MACRO] Reset the length of a dynamic array to 0.
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91
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92 Dynarr_free(d)
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93 Destroy a dynamic array and the memory allocated to it.
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94
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95 Use the following global variable:
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96
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97 Dynarr_min_size
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98 Minimum allowable size for a dynamic array when it is resized. The
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99 default is 32 and does not normally need to be changed.
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100
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101 */
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102
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103 #include <config.h>
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104 #include "lisp.h"
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105
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106 int Dynarr_min_size = 1;
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107
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108 void *
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109 Dynarr_newf (int elsize)
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110 {
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111 Dynarr *d = (Dynarr *) xmalloc (sizeof (Dynarr));
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112
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113 memset (d, 0, sizeof (*d));
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114 d->elsize = elsize;
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115
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116 return d;
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117 }
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118
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119 void
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120 Dynarr_resize (void *d, int size)
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121 {
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122 int newsize;
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123 double multiplier;
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124 Dynarr *dy = (Dynarr *) d;
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125
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126 if (dy->max <= 8)
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127 multiplier = 2;
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128 else
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129 multiplier = 1.5;
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130
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131 for (newsize = dy->max; newsize < size;)
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132 newsize = max (Dynarr_min_size, multiplier * newsize);
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133
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134 /* Don't do anything if the array is already big enough. */
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135 if (newsize > dy->max)
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136 {
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137 dy->base = xrealloc (dy->base, newsize*dy->elsize);
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138 dy->max = newsize;
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139 }
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140 }
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141
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142 /* Add a number of contiguous elements to the array starting at START. */
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143 void
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144 Dynarr_insert_many (void *d, CONST void *el, int len, int start)
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145 {
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146 Dynarr *dy = (Dynarr *) d;
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147
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148 Dynarr_resize (dy, dy->cur+len);
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149 /* Silently adjust start to be valid. */
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150 if (start > dy->cur)
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151 start = dy->cur;
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152 else if (start < 0)
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153 start = 0;
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154
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155 if (start != dy->cur)
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156 {
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157 memmove ((char *) dy->base + (start + len)*dy->elsize,
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158 (char *) dy->base + start*dy->elsize,
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159 (dy->cur - start)*dy->elsize);
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160 }
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161 memcpy ((char *) dy->base + start*dy->elsize, el, len*dy->elsize);
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162 dy->cur += len;
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163
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164 if (dy->cur > dy->largest)
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165 dy->largest = dy->cur;
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166 }
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167
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168 void
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169 Dynarr_delete_many (void *d, int start, int len)
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170 {
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171 Dynarr *dy = (Dynarr *) d;
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172
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173 assert (start >= 0 && len >= 0 && start + len <= dy->cur);
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174 memmove ((char *) dy->base + start*dy->elsize,
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175 (char *) dy->base + (start + len)*dy->elsize,
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176 (dy->cur - start - len)*dy->elsize);
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177 dy->cur -= len;
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178 }
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179
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180 void
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181 Dynarr_free (void *d)
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182 {
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183 Dynarr *dy = (Dynarr *) d;
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184
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185 if (dy->base)
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186 xfree (dy->base);
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187 xfree (dy);
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188 }
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189
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190 #ifdef MEMORY_USAGE_STATS
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191
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192 /* Return memory usage for Dynarr D. The returned value is the total
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193 amount of bytes actually being used for the Dynarr, including all
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194 overhead. The extra amount of space in the Dynarr that is
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195 allocated beyond what was requested is returned in DYNARR_OVERHEAD
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196 in STATS. The extra amount of space that malloc() allocates beyond
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197 what was requested of it is returned in MALLOC_OVERHEAD in STATS.
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198 See the comment above the definition of this structure. */
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199
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200 int
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201 Dynarr_memory_usage (void *d, struct overhead_stats *stats)
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202 {
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203 int total = 0;
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204 Dynarr *dy = (Dynarr *) d;
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205
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206 /* We have to be a bit tricky here because not all of the
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207 memory that malloc() will claim as "requested" was actually
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208 requested. */
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209
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210 if (dy->base)
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211 {
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212 int malloc_used = malloced_storage_size (dy->base,
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213 dy->elsize * dy->max, 0);
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214 /* #### This may or may not be correct. Some Dynarrs would
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215 prefer that we use dy->cur instead of dy->largest here. */
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216 int was_requested = dy->elsize * dy->largest;
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217 int dynarr_overhead = dy->elsize * (dy->max - dy->largest);
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218
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219 total += malloc_used;
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220 stats->was_requested += was_requested;
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221 stats->dynarr_overhead += dynarr_overhead;
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222 /* And the remainder must be malloc overhead. */
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223 stats->malloc_overhead +=
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224 malloc_used - was_requested - dynarr_overhead;
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225 }
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226
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227 total += malloced_storage_size (d, sizeof (*dy), stats);
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228
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229 return total;
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230 }
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231
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232 #endif
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