annotate src/hashtab.c @ 7897:43071dab7621 v7.4.1245

commit https://github.com/vim/vim/commit/d087566a419cc107adab77db997b184ea0e433ad Author: Bram Moolenaar <Bram@vim.org> Date: Tue Feb 2 20:52:42 2016 +0100 patch 7.4.1245 Problem: File missing from distribution. Solution: Add json_test.c.
author Christian Brabandt <cb@256bit.org>
date Tue, 02 Feb 2016 21:00:08 +0100
parents bcef391c101c
children 9fa567d13551
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1 /* vi:set ts=8 sts=4 sw=4:
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2 *
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3 * VIM - Vi IMproved by Bram Moolenaar
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4 *
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5 * Do ":help uganda" in Vim to read copying and usage conditions.
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6 * Do ":help credits" in Vim to see a list of people who contributed.
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7 * See README.txt for an overview of the Vim source code.
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8 */
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9
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10 /*
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11 * hashtab.c: Handling of a hashtable with Vim-specific properties.
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12 *
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13 * Each item in a hashtable has a NUL terminated string key. A key can appear
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14 * only once in the table.
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15 *
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16 * A hash number is computed from the key for quick lookup. When the hashes
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17 * of two different keys point to the same entry an algorithm is used to
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18 * iterate over other entries in the table until the right one is found.
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19 * To make the iteration work removed keys are different from entries where a
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20 * key was never present.
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21 *
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22 * The mechanism has been partly based on how Python Dictionaries are
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23 * implemented. The algorithm is from Knuth Vol. 3, Sec. 6.4.
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24 *
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25 * The hashtable grows to accommodate more entries when needed. At least 1/3
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26 * of the entries is empty to keep the lookup efficient (at the cost of extra
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27 * memory).
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28 */
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29
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30 #include "vim.h"
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31
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32 #if defined(FEAT_EVAL) || defined(FEAT_SYN_HL) || defined(PROTO)
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33
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34 #if 0
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35 # define HT_DEBUG /* extra checks for table consistency and statistics */
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36
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37 static long hash_count_lookup = 0; /* count number of hashtab lookups */
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38 static long hash_count_perturb = 0; /* count number of "misses" */
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39 #endif
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40
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41 /* Magic value for algorithm that walks through the array. */
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42 #define PERTURB_SHIFT 5
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43
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44 static int hash_may_resize(hashtab_T *ht, int minitems);
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45
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46 #if 0 /* currently not used */
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47 /*
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48 * Create an empty hash table.
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49 * Returns NULL when out of memory.
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50 */
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51 hashtab_T *
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52 hash_create(void)
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53 {
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54 hashtab_T *ht;
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55
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56 ht = (hashtab_T *)alloc(sizeof(hashtab_T));
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57 if (ht != NULL)
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58 hash_init(ht);
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59 return ht;
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60 }
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61 #endif
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62
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63 /*
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64 * Initialize an empty hash table.
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65 */
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66 void
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67 hash_init(hashtab_T *ht)
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68 {
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69 /* This zeroes all "ht_" entries and all the "hi_key" in "ht_smallarray". */
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70 vim_memset(ht, 0, sizeof(hashtab_T));
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71 ht->ht_array = ht->ht_smallarray;
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72 ht->ht_mask = HT_INIT_SIZE - 1;
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73 }
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74
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75 /*
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76 * Free the array of a hash table. Does not free the items it contains!
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77 * If "ht" is not freed then you should call hash_init() next!
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78 */
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79 void
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80 hash_clear(hashtab_T *ht)
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81 {
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82 if (ht->ht_array != ht->ht_smallarray)
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83 vim_free(ht->ht_array);
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84 }
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85
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86 /*
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87 * Free the array of a hash table and all the keys it contains. The keys must
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88 * have been allocated. "off" is the offset from the start of the allocate
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89 * memory to the location of the key (it's always positive).
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90 */
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91 void
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92 hash_clear_all(hashtab_T *ht, int off)
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93 {
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94 long todo;
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95 hashitem_T *hi;
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96
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97 todo = (long)ht->ht_used;
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98 for (hi = ht->ht_array; todo > 0; ++hi)
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99 {
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100 if (!HASHITEM_EMPTY(hi))
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101 {
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102 vim_free(hi->hi_key - off);
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103 --todo;
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104 }
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105 }
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106 hash_clear(ht);
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107 }
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108
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109 /*
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110 * Find "key" in hashtable "ht". "key" must not be NULL.
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111 * Always returns a pointer to a hashitem. If the item was not found then
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112 * HASHITEM_EMPTY() is TRUE. The pointer is then the place where the key
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113 * would be added.
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114 * WARNING: The returned pointer becomes invalid when the hashtable is changed
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115 * (adding, setting or removing an item)!
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116 */
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117 hashitem_T *
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118 hash_find(hashtab_T *ht, char_u *key)
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119 {
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120 return hash_lookup(ht, key, hash_hash(key));
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121 }
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122
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123 /*
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124 * Like hash_find(), but caller computes "hash".
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125 */
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126 hashitem_T *
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127 hash_lookup(hashtab_T *ht, char_u *key, hash_T hash)
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128 {
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129 hash_T perturb;
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130 hashitem_T *freeitem;
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131 hashitem_T *hi;
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132 unsigned idx;
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133
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134 #ifdef HT_DEBUG
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135 ++hash_count_lookup;
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136 #endif
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137
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138 /*
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139 * Quickly handle the most common situations:
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140 * - return if there is no item at all
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141 * - skip over a removed item
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142 * - return if the item matches
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143 */
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144 idx = (unsigned)(hash & ht->ht_mask);
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145 hi = &ht->ht_array[idx];
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146
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147 if (hi->hi_key == NULL)
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148 return hi;
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149 if (hi->hi_key == HI_KEY_REMOVED)
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150 freeitem = hi;
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151 else if (hi->hi_hash == hash && STRCMP(hi->hi_key, key) == 0)
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152 return hi;
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153 else
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154 freeitem = NULL;
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155
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156 /*
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157 * Need to search through the table to find the key. The algorithm
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158 * to step through the table starts with large steps, gradually becoming
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159 * smaller down to (1/4 table size + 1). This means it goes through all
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160 * table entries in the end.
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161 * When we run into a NULL key it's clear that the key isn't there.
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162 * Return the first available slot found (can be a slot of a removed
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163 * item).
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164 */
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165 for (perturb = hash; ; perturb >>= PERTURB_SHIFT)
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166 {
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167 #ifdef HT_DEBUG
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168 ++hash_count_perturb; /* count a "miss" for hashtab lookup */
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169 #endif
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170 idx = (unsigned)((idx << 2U) + idx + perturb + 1U);
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171 hi = &ht->ht_array[idx & ht->ht_mask];
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172 if (hi->hi_key == NULL)
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173 return freeitem == NULL ? hi : freeitem;
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174 if (hi->hi_hash == hash
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175 && hi->hi_key != HI_KEY_REMOVED
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176 && STRCMP(hi->hi_key, key) == 0)
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177 return hi;
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178 if (hi->hi_key == HI_KEY_REMOVED && freeitem == NULL)
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179 freeitem = hi;
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180 }
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181 }
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182
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183 /*
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184 * Print the efficiency of hashtable lookups.
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185 * Useful when trying different hash algorithms.
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186 * Called when exiting.
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187 */
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188 void
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189 hash_debug_results(void)
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190 {
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191 #ifdef HT_DEBUG
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192 fprintf(stderr, "\r\n\r\n\r\n\r\n");
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193 fprintf(stderr, "Number of hashtable lookups: %ld\r\n", hash_count_lookup);
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194 fprintf(stderr, "Number of perturb loops: %ld\r\n", hash_count_perturb);
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195 fprintf(stderr, "Percentage of perturb loops: %ld%%\r\n",
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196 hash_count_perturb * 100 / hash_count_lookup);
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197 #endif
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198 }
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199
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200 /*
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201 * Add item with key "key" to hashtable "ht".
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202 * Returns FAIL when out of memory or the key is already present.
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203 */
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204 int
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205 hash_add(hashtab_T *ht, char_u *key)
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206 {
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207 hash_T hash = hash_hash(key);
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208 hashitem_T *hi;
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209
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210 hi = hash_lookup(ht, key, hash);
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211 if (!HASHITEM_EMPTY(hi))
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212 {
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213 EMSG2(_(e_intern2), "hash_add()");
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214 return FAIL;
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215 }
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216 return hash_add_item(ht, hi, key, hash);
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217 }
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218
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219 /*
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220 * Add item "hi" with "key" to hashtable "ht". "key" must not be NULL and
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221 * "hi" must have been obtained with hash_lookup() and point to an empty item.
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222 * "hi" is invalid after this!
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223 * Returns OK or FAIL (out of memory).
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224 */
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225 int
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226 hash_add_item(
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227 hashtab_T *ht,
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228 hashitem_T *hi,
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229 char_u *key,
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230 hash_T hash)
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231 {
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232 /* If resizing failed before and it fails again we can't add an item. */
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233 if (ht->ht_error && hash_may_resize(ht, 0) == FAIL)
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234 return FAIL;
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235
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236 ++ht->ht_used;
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237 if (hi->hi_key == NULL)
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238 ++ht->ht_filled;
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239 hi->hi_key = key;
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240 hi->hi_hash = hash;
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241
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242 /* When the space gets low may resize the array. */
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243 return hash_may_resize(ht, 0);
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244 }
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245
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246 #if 0 /* not used */
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247 /*
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248 * Overwrite hashtable item "hi" with "key". "hi" must point to the item that
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249 * is to be overwritten. Thus the number of items in the hashtable doesn't
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250 * change.
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251 * Although the key must be identical, the pointer may be different, thus it's
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252 * set anyway (the key is part of an item with that key).
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253 * The caller must take care of freeing the old item.
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254 * "hi" is invalid after this!
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255 */
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256 void
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257 hash_set(hashitem_T *hi, char_u *key)
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258 {
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259 hi->hi_key = key;
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260 }
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261 #endif
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262
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263 /*
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264 * Remove item "hi" from hashtable "ht". "hi" must have been obtained with
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265 * hash_lookup().
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266 * The caller must take care of freeing the item itself.
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267 */
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268 void
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269 hash_remove(hashtab_T *ht, hashitem_T *hi)
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270 {
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271 --ht->ht_used;
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272 hi->hi_key = HI_KEY_REMOVED;
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273 hash_may_resize(ht, 0);
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274 }
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275
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276 /*
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277 * Lock a hashtable: prevent that ht_array changes.
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278 * Don't use this when items are to be added!
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279 * Must call hash_unlock() later.
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280 */
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281 void
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282 hash_lock(hashtab_T *ht)
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283 {
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284 ++ht->ht_locked;
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285 }
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286
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287 #if 0 /* currently not used */
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288 /*
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289 * Lock a hashtable at the specified number of entries.
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290 * Caller must make sure no more than "size" entries will be added.
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291 * Must call hash_unlock() later.
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292 */
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293 void
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294 hash_lock_size(hashtab_T *ht, int size)
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295 {
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296 (void)hash_may_resize(ht, size);
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297 ++ht->ht_locked;
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298 }
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299 #endif
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300
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301 /*
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302 * Unlock a hashtable: allow ht_array changes again.
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303 * Table will be resized (shrink) when necessary.
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304 * This must balance a call to hash_lock().
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305 */
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306 void
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307 hash_unlock(hashtab_T *ht)
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308 {
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309 --ht->ht_locked;
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310 (void)hash_may_resize(ht, 0);
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311 }
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312
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313 /*
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314 * Shrink a hashtable when there is too much empty space.
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315 * Grow a hashtable when there is not enough empty space.
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316 * Returns OK or FAIL (out of memory).
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317 */
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318 static int
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319 hash_may_resize(
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320 hashtab_T *ht,
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321 int minitems) /* minimal number of items */
799
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322 {
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323 hashitem_T temparray[HT_INIT_SIZE];
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324 hashitem_T *oldarray, *newarray;
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325 hashitem_T *olditem, *newitem;
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326 unsigned newi;
799
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327 int todo;
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328 long_u oldsize, newsize;
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329 long_u minsize;
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330 long_u newmask;
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331 hash_T perturb;
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332
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333 /* Don't resize a locked table. */
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334 if (ht->ht_locked > 0)
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335 return OK;
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336
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337 #ifdef HT_DEBUG
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338 if (ht->ht_used > ht->ht_filled)
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339 EMSG("hash_may_resize(): more used than filled");
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340 if (ht->ht_filled >= ht->ht_mask + 1)
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341 EMSG("hash_may_resize(): table completely filled");
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342 #endif
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343
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344 if (minitems == 0)
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345 {
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346 /* Return quickly for small tables with at least two NULL items. NULL
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347 * items are required for the lookup to decide a key isn't there. */
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348 if (ht->ht_filled < HT_INIT_SIZE - 1
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349 && ht->ht_array == ht->ht_smallarray)
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350 return OK;
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351
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352 /*
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353 * Grow or refill the array when it's more than 2/3 full (including
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354 * removed items, so that they get cleaned up).
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355 * Shrink the array when it's less than 1/5 full. When growing it is
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356 * at least 1/4 full (avoids repeated grow-shrink operations)
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357 */
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358 oldsize = ht->ht_mask + 1;
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359 if (ht->ht_filled * 3 < oldsize * 2 && ht->ht_used > oldsize / 5)
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360 return OK;
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diff changeset
361
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
362 if (ht->ht_used > 1000)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
363 minsize = ht->ht_used * 2; /* it's big, don't make too much room */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
364 else
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
365 minsize = ht->ht_used * 4; /* make plenty of room */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
366 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
367 else
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
368 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
369 /* Use specified size. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
370 if ((long_u)minitems < ht->ht_used) /* just in case... */
835
8bebcabccc2c updated for version 7.0e01
vimboss
parents: 799
diff changeset
371 minitems = (int)ht->ht_used;
799
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
372 minsize = minitems * 3 / 2; /* array is up to 2/3 full */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
373 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
374
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
375 newsize = HT_INIT_SIZE;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
376 while (newsize < minsize)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
377 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
378 newsize <<= 1; /* make sure it's always a power of 2 */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
379 if (newsize == 0)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
380 return FAIL; /* overflow */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
381 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
382
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
383 if (newsize == HT_INIT_SIZE)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
384 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
385 /* Use the small array inside the hashdict structure. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
386 newarray = ht->ht_smallarray;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
387 if (ht->ht_array == newarray)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
388 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
389 /* Moving from ht_smallarray to ht_smallarray! Happens when there
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
390 * are many removed items. Copy the items to be able to clean up
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
391 * removed items. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
392 mch_memmove(temparray, newarray, sizeof(temparray));
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
393 oldarray = temparray;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
394 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
395 else
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
396 oldarray = ht->ht_array;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
397 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
398 else
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
399 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
400 /* Allocate an array. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
401 newarray = (hashitem_T *)alloc((unsigned)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
402 (sizeof(hashitem_T) * newsize));
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
403 if (newarray == NULL)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
404 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
405 /* Out of memory. When there are NULL items still return OK.
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
406 * Otherwise set ht_error, because lookup may result in a hang if
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
407 * we add another item. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
408 if (ht->ht_filled < ht->ht_mask)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
409 return OK;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
410 ht->ht_error = TRUE;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
411 return FAIL;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
412 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
413 oldarray = ht->ht_array;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
414 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
415 vim_memset(newarray, 0, (size_t)(sizeof(hashitem_T) * newsize));
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
416
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
417 /*
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
418 * Move all the items from the old array to the new one, placing them in
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
419 * the right spot. The new array won't have any removed items, thus this
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
420 * is also a cleanup action.
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
421 */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
422 newmask = newsize - 1;
835
8bebcabccc2c updated for version 7.0e01
vimboss
parents: 799
diff changeset
423 todo = (int)ht->ht_used;
799
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
424 for (olditem = oldarray; todo > 0; ++olditem)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
425 if (!HASHITEM_EMPTY(olditem))
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
426 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
427 /*
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
428 * The algorithm to find the spot to add the item is identical to
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
429 * the algorithm to find an item in hash_lookup(). But we only
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
430 * need to search for a NULL key, thus it's simpler.
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
431 */
3970
2c12cd5c1381 updated for version 7.3.740
Bram Moolenaar <bram@vim.org>
parents: 2520
diff changeset
432 newi = (unsigned)(olditem->hi_hash & newmask);
799
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
433 newitem = &newarray[newi];
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
434
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
435 if (newitem->hi_key != NULL)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
436 for (perturb = olditem->hi_hash; ; perturb >>= PERTURB_SHIFT)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
437 {
3970
2c12cd5c1381 updated for version 7.3.740
Bram Moolenaar <bram@vim.org>
parents: 2520
diff changeset
438 newi = (unsigned)((newi << 2U) + newi + perturb + 1U);
799
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
439 newitem = &newarray[newi & newmask];
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
440 if (newitem->hi_key == NULL)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
441 break;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
442 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
443 *newitem = *olditem;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
444 --todo;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
445 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
446
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
447 if (ht->ht_array != ht->ht_smallarray)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
448 vim_free(ht->ht_array);
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
449 ht->ht_array = newarray;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
450 ht->ht_mask = newmask;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
451 ht->ht_filled = ht->ht_used;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
452 ht->ht_error = FALSE;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
453
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
454 return OK;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
455 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
456
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
457 /*
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
458 * Get the hash number for a key.
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
459 * If you think you know a better hash function: Compile with HT_DEBUG set and
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
460 * run a script that uses hashtables a lot. Vim will then print statistics
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
461 * when exiting. Try that with the current hash algorithm and yours. The
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
462 * lower the percentage the better.
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
463 */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
464 hash_T
7823
bcef391c101c commit https://github.com/vim/vim/commit/68c2f638e65d914dc6e84eb7ce2624f08af525c0
Christian Brabandt <cb@256bit.org>
parents: 7803
diff changeset
465 hash_hash(char_u *key)
799
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
466 {
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
467 hash_T hash;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
468 char_u *p;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
469
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
470 if ((hash = *key) == 0)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
471 return (hash_T)0; /* Empty keys are not allowed, but we don't
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
472 want to crash if we get one. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
473 p = key + 1;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
474
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
475 /* A simplistic algorithm that appears to do very well.
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
476 * Suggested by George Reilly. */
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
477 while (*p != NUL)
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
478 hash = hash * 101 + *p++;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
479
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
480 return hash;
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
481 }
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
482
6beb2c667935 updated for version 7.0b
vimboss
parents:
diff changeset
483 #endif