1 | /* Constant string caching for GNU Make.
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2 | Copyright (C) 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
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3 | This file is part of GNU Make.
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4 |
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5 | GNU Make is free software; you can redistribute it and/or modify it under the
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6 | terms of the GNU General Public License as published by the Free Software
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7 | Foundation; either version 3 of the License, or (at your option) any later
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8 | version.
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9 |
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10 | GNU Make is distributed in the hope that it will be useful, but WITHOUT ANY
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11 | WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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12 | A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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13 |
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14 | You should have received a copy of the GNU General Public License along with
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15 | this program. If not, see <http://www.gnu.org/licenses/>. */
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16 |
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17 | #include "make.h"
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18 | #ifndef CONFIG_WITH_STRCACHE2
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19 |
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20 | #include <assert.h>
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21 |
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22 | #include "hash.h"
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23 |
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24 | /* The size (in bytes) of each cache buffer.
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25 | Try to pick something that will map well into the heap. */
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26 | #define CACHE_BUFFER_SIZE (8192 - 16)
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27 |
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28 |
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29 | /* A string cached here will never be freed, so we don't need to worry about
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30 | reference counting. We just store the string, and then remember it in a
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31 | hash so it can be looked up again. */
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32 |
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33 | struct strcache {
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34 | struct strcache *next; /* The next block of strings. */
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35 | char *end; /* Pointer to the beginning of the free space. */
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36 | int count; /* # of strings in this buffer (for stats). */
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37 | int bytesfree; /* The amount of the buffer that is free. */
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38 | char buffer[1]; /* The buffer comes after this. */
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39 | };
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40 |
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41 | static int bufsize = CACHE_BUFFER_SIZE;
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42 | static struct strcache *strcache = NULL;
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43 |
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44 | /* Add a new buffer to the cache. Add it at the front to reduce search time.
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45 | This can also increase the overhead, since it's less likely that older
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46 | buffers will be filled in. However, GNU make has so many smaller strings
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47 | that this doesn't seem to be much of an issue in practice.
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48 | */
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49 | static struct strcache *
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50 | new_cache()
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51 | {
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52 | struct strcache *new;
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53 | new = xmalloc (sizeof (*new) + bufsize);
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54 | new->end = new->buffer;
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55 | new->count = 0;
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56 | new->bytesfree = bufsize;
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57 |
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58 | new->next = strcache;
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59 | strcache = new;
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60 |
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61 | return new;
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62 | }
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63 |
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64 | static const char *
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65 | add_string(const char *str, int len)
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66 | {
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67 | struct strcache *best = NULL;
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68 | struct strcache *sp;
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69 | const char *res;
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70 |
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71 | /* If the string we want is too large to fit into a single buffer, then
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72 | we're screwed; nothing will ever fit! Change the maximum size of the
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73 | cache to be big enough. */
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74 | if (len > bufsize)
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75 | bufsize = len * 2;
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76 |
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77 | /* First, find a cache with enough free space. We always look through all
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78 | the blocks and choose the one with the best fit (the one that leaves the
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79 | least amount of space free). */
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80 | for (sp = strcache; sp != NULL; sp = sp->next)
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81 | if (sp->bytesfree > len && (!best || best->bytesfree > sp->bytesfree))
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82 | best = sp;
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83 |
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84 | /* If nothing is big enough, make a new cache. */
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85 | if (!best)
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86 | best = new_cache();
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87 |
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88 | assert (best->bytesfree > len);
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89 |
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90 | /* Add the string to the best cache. */
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91 | res = best->end;
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92 | memcpy (best->end, str, len);
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93 | best->end += len;
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94 | *(best->end++) = '\0';
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95 | best->bytesfree -= len + 1;
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96 | ++best->count;
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97 |
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98 | return res;
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99 | }
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100 |
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101 |
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102 | /* Hash table of strings in the cache. */
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103 |
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104 | static unsigned long
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105 | str_hash_1 (const void *key)
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106 | {
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107 | return_ISTRING_HASH_1 ((const char *) key);
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108 | }
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109 |
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110 | static unsigned long
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111 | str_hash_2 (const void *key)
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112 | {
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113 | return_ISTRING_HASH_2 ((const char *) key);
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114 | }
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115 |
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116 | static int
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117 | str_hash_cmp (const void *x, const void *y)
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118 | {
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119 | return_ISTRING_COMPARE ((const char *) x, (const char *) y);
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120 | }
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121 |
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122 | static struct hash_table strings;
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123 | static unsigned long total_adds = 0;
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124 |
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125 | static const char *
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126 | add_hash (const char *str, int len)
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127 | {
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128 | /* Look up the string in the hash. If it's there, return it. */
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129 | char *const *slot = (char *const *) hash_find_slot (&strings, str);
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130 | const char *key = *slot;
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131 |
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132 | /* Count the total number of adds we performed. */
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133 | ++total_adds;
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134 |
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135 | if (!HASH_VACANT (key))
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136 | return key;
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137 |
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138 | /* Not there yet so add it to a buffer, then into the hash table. */
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139 | key = add_string (str, len);
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140 | hash_insert_at (&strings, key, slot);
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141 | return key;
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142 | }
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143 |
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144 | /* Returns true if the string is in the cache; false if not. */
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145 | int
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146 | strcache_iscached (const char *str)
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147 | {
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148 | struct strcache *sp;
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149 |
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150 | for (sp = strcache; sp != 0; sp = sp->next)
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151 | if (str >= sp->buffer && str < sp->end)
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152 | return 1;
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153 |
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154 | return 0;
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155 | }
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156 |
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157 | /* If the string is already in the cache, return a pointer to the cached
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158 | version. If not, add it then return a pointer to the cached version.
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159 | Note we do NOT take control of the string passed in. */
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160 | const char *
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161 | strcache_add (const char *str)
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162 | {
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163 | return add_hash (str, strlen (str));
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164 | }
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165 |
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166 | const char *
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167 | strcache_add_len (const char *str, int len)
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168 | {
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169 | /* If we're not given a nul-terminated string we have to create one, because
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170 | the hashing functions expect it. */
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171 | if (str[len] != '\0')
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172 | {
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173 | char *key = alloca (len + 1);
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174 | memcpy (key, str, len);
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175 | key[len] = '\0';
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176 | str = key;
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177 | }
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178 |
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179 | return add_hash (str, len);
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180 | }
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181 |
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182 | int
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183 | strcache_setbufsize(int size)
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184 | {
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185 | if (size > bufsize)
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186 | bufsize = size;
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187 | return bufsize;
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188 | }
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189 |
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190 | void
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191 | strcache_init (void)
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192 | {
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193 | hash_init (&strings, 8000, str_hash_1, str_hash_2, str_hash_cmp);
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194 | }
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195 |
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196 |
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197 | /* Generate some stats output. */
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198 |
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199 | void
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200 | strcache_print_stats (const char *prefix)
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201 | {
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202 | int numbuffs = 0, numstrs = 0;
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203 | int totsize = 0, avgsize, maxsize = 0, minsize = bufsize;
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204 | int totfree = 0, avgfree, maxfree = 0, minfree = bufsize;
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205 | int lastused = 0, lastfree = 0;
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206 |
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207 | if (strcache)
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208 | {
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209 | const struct strcache *sp;
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210 |
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211 | /* Count the first buffer separately since it's not full. */
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212 | lastused = strcache->end - strcache->buffer;
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213 | lastfree = strcache->bytesfree;
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214 |
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215 | for (sp = strcache->next; sp != NULL; sp = sp->next)
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216 | {
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217 | int bf = sp->bytesfree;
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218 | int sz = sp->end - sp->buffer;
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219 |
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220 | ++numbuffs;
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221 | numstrs += sp->count;
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222 |
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223 | totsize += sz;
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224 | maxsize = (sz > maxsize ? sz : maxsize);
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225 | minsize = (sz < minsize ? sz : minsize);
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226 |
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227 | totfree += bf;
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228 | maxfree = (bf > maxfree ? bf : maxfree);
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229 | minfree = (bf < minfree ? bf : minfree);
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230 | }
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231 | }
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232 |
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233 | avgsize = numbuffs ? (int)(totsize / numbuffs) : 0;
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234 | avgfree = numbuffs ? (int)(totfree / numbuffs) : 0;
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235 |
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236 | printf (_("\n%s # of strings in strcache: %d / lookups = %lu / hits = %lu\n"),
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237 | prefix, numstrs, total_adds, (total_adds - numstrs));
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238 | printf (_("%s # of strcache buffers: %d (* %d B/buffer = %d B)\n"),
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239 | prefix, (numbuffs + 1), bufsize, ((numbuffs + 1) * bufsize));
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240 | printf (_("%s strcache used: total = %d (%d) / max = %d / min = %d / avg = %d\n"),
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241 | prefix, totsize, lastused, maxsize, minsize, avgsize);
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242 | printf (_("%s strcache free: total = %d (%d) / max = %d / min = %d / avg = %d\n"),
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243 | prefix, totfree, lastfree, maxfree, minfree, avgfree);
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244 |
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245 | fputs (_("\n# strcache hash-table stats:\n# "), stdout);
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246 | hash_print_stats (&strings, stdout);
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247 | }
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248 |
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249 | #else /* CONFIG_WITH_STRCACHE2 */
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250 |
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251 | #include "strcache2.h"
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252 |
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253 | const char *suffixes_strcached;
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254 |
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255 | /* The file string cache. */
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256 | struct strcache2 file_strcache;
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257 |
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258 | void strcache_init (void)
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259 | {
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260 | strcache2_init(&file_strcache,
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261 | "file", /* name */
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262 | 65536, /* hash size */
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263 | 0, /* default segment size*/
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264 | #ifdef HAVE_CASE_INSENSITIVE_FS
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265 | 1, /* case insensitive */
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266 | #else
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267 | 0, /* case insensitive */
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268 | #endif
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269 | 0); /* thread safe */
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270 |
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271 | /* .SUFFIXES is referenced in several loops, keep the added pointer in a
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272 | global var so these can be optimized. */
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273 |
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274 | suffixes_strcached = strcache_add_len (".SUFFIXES", sizeof (".SUFFIXES")-1);
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275 | }
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276 |
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277 | void
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278 | strcache_print_stats (const char *prefix)
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279 | {
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280 | strcache2_print_stats (&file_strcache, prefix);
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281 | }
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282 |
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283 | #endif /* CONFIG_WITH_STRCACHE2 */
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284 |
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