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0
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1 /* An expandable hash tables datatype.
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2 Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004
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3 Free Software Foundation, Inc.
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4 Contributed by Vladimir Makarov (vmakarov@cygnus.com).
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5
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6 This file is part of the libiberty library.
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7 Libiberty is free software; you can redistribute it and/or
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8 modify it under the terms of the GNU Library General Public
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9 License as published by the Free Software Foundation; either
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10 version 2 of the License, or (at your option) any later version.
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11
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12 Libiberty is distributed in the hope that it will be useful,
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13 but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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15 Library General Public License for more details.
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16
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17 You should have received a copy of the GNU Library General Public
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18 License along with libiberty; see the file COPYING.LIB. If
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19 not, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
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20 Boston, MA 02110-1301, USA. */
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21
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22 /* This package implements basic hash table functionality. It is possible
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23 to search for an entry, create an entry and destroy an entry.
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24
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25 Elements in the table are generic pointers.
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26
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27 The size of the table is not fixed; if the occupancy of the table
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28 grows too high the hash table will be expanded.
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29
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30 The abstract data implementation is based on generalized Algorithm D
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31 from Knuth's book "The art of computer programming". Hash table is
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32 expanded by creation of new hash table and transferring elements from
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33 the old table to the new table. */
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34
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35 #ifdef HAVE_CONFIG_H
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36 #include "config.h"
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37 #endif
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38
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39 #include <sys/types.h>
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40
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41 #ifdef HAVE_STDLIB_H
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42 #include <stdlib.h>
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43 #endif
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44 #ifdef HAVE_STRING_H
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45 #include <string.h>
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46 #endif
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47 #ifdef HAVE_MALLOC_H
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48 #include <malloc.h>
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49 #endif
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50 #ifdef HAVE_LIMITS_H
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51 #include <limits.h>
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52 #endif
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53 #ifdef HAVE_STDINT_H
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54 #include <stdint.h>
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55 #endif
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56
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57 #include <stdio.h>
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58
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59 #include "libiberty.h"
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60 #include "ansidecl.h"
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61 #include "hashtab.h"
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62
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63 #ifndef CHAR_BIT
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64 #define CHAR_BIT 8
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65 #endif
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66
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67 static unsigned int higher_prime_index (unsigned long);
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68 static hashval_t htab_mod_1 (hashval_t, hashval_t, hashval_t, int);
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69 static hashval_t htab_mod (hashval_t, htab_t);
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70 static hashval_t htab_mod_m2 (hashval_t, htab_t);
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71 static hashval_t hash_pointer (const void *);
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72 static int eq_pointer (const void *, const void *);
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73 static int htab_expand (htab_t);
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74 static PTR *find_empty_slot_for_expand (htab_t, hashval_t);
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75
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76 /* At some point, we could make these be NULL, and modify the
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77 hash-table routines to handle NULL specially; that would avoid
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78 function-call overhead for the common case of hashing pointers. */
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79 htab_hash htab_hash_pointer = hash_pointer;
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80 htab_eq htab_eq_pointer = eq_pointer;
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81
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82 /* Table of primes and multiplicative inverses.
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83
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84 Note that these are not minimally reduced inverses. Unlike when generating
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85 code to divide by a constant, we want to be able to use the same algorithm
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86 all the time. All of these inverses (are implied to) have bit 32 set.
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87
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88 For the record, here's the function that computed the table; it's a
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89 vastly simplified version of the function of the same name from gcc. */
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90
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91 #if 0
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92 unsigned int
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93 ceil_log2 (unsigned int x)
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94 {
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95 int i;
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96 for (i = 31; i >= 0 ; --i)
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97 if (x > (1u << i))
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98 return i+1;
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99 abort ();
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100 }
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101
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102 unsigned int
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103 choose_multiplier (unsigned int d, unsigned int *mlp, unsigned char *shiftp)
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104 {
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105 unsigned long long mhigh;
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106 double nx;
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107 int lgup, post_shift;
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108 int pow, pow2;
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109 int n = 32, precision = 32;
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110
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111 lgup = ceil_log2 (d);
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112 pow = n + lgup;
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113 pow2 = n + lgup - precision;
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114
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115 nx = ldexp (1.0, pow) + ldexp (1.0, pow2);
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116 mhigh = nx / d;
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117
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118 *shiftp = lgup - 1;
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119 *mlp = mhigh;
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120 return mhigh >> 32;
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121 }
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122 #endif
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123
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124 struct prime_ent
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125 {
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126 hashval_t prime;
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127 hashval_t inv;
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128 hashval_t inv_m2; /* inverse of prime-2 */
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129 hashval_t shift;
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130 };
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131
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132 static struct prime_ent const prime_tab[] = {
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133 { 7, 0x24924925, 0x9999999b, 2 },
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134 { 13, 0x3b13b13c, 0x745d1747, 3 },
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135 { 31, 0x08421085, 0x1a7b9612, 4 },
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136 { 61, 0x0c9714fc, 0x15b1e5f8, 5 },
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137 { 127, 0x02040811, 0x0624dd30, 6 },
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138 { 251, 0x05197f7e, 0x073260a5, 7 },
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139 { 509, 0x01824366, 0x02864fc8, 8 },
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140 { 1021, 0x00c0906d, 0x014191f7, 9 },
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141 { 2039, 0x0121456f, 0x0161e69e, 10 },
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142 { 4093, 0x00300902, 0x00501908, 11 },
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143 { 8191, 0x00080041, 0x00180241, 12 },
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144 { 16381, 0x000c0091, 0x00140191, 13 },
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145 { 32749, 0x002605a5, 0x002a06e6, 14 },
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146 { 65521, 0x000f00e2, 0x00110122, 15 },
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147 { 131071, 0x00008001, 0x00018003, 16 },
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148 { 262139, 0x00014002, 0x0001c004, 17 },
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149 { 524287, 0x00002001, 0x00006001, 18 },
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150 { 1048573, 0x00003001, 0x00005001, 19 },
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151 { 2097143, 0x00004801, 0x00005801, 20 },
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152 { 4194301, 0x00000c01, 0x00001401, 21 },
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153 { 8388593, 0x00001e01, 0x00002201, 22 },
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154 { 16777213, 0x00000301, 0x00000501, 23 },
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155 { 33554393, 0x00001381, 0x00001481, 24 },
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156 { 67108859, 0x00000141, 0x000001c1, 25 },
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157 { 134217689, 0x000004e1, 0x00000521, 26 },
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158 { 268435399, 0x00000391, 0x000003b1, 27 },
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159 { 536870909, 0x00000019, 0x00000029, 28 },
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160 { 1073741789, 0x0000008d, 0x00000095, 29 },
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161 { 2147483647, 0x00000003, 0x00000007, 30 },
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162 /* Avoid "decimal constant so large it is unsigned" for 4294967291. */
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163 { 0xfffffffb, 0x00000006, 0x00000008, 31 }
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164 };
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165
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166 /* The following function returns an index into the above table of the
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167 nearest prime number which is greater than N, and near a power of two. */
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168
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169 static unsigned int
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170 higher_prime_index (unsigned long n)
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171 {
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172 unsigned int low = 0;
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173 unsigned int high = sizeof(prime_tab) / sizeof(prime_tab[0]);
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174
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175 while (low != high)
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176 {
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177 unsigned int mid = low + (high - low) / 2;
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178 if (n > prime_tab[mid].prime)
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179 low = mid + 1;
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180 else
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181 high = mid;
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182 }
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183
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184 /* If we've run out of primes, abort. */
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185 if (n > prime_tab[low].prime)
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186 {
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187 fprintf (stderr, "Cannot find prime bigger than %lu\n", n);
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188 abort ();
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189 }
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190
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191 return low;
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192 }
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193
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194 /* Returns a hash code for P. */
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195
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196 static hashval_t
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197 hash_pointer (const PTR p)
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198 {
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199 return (hashval_t) ((long)p >> 3);
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200 }
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201
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202 /* Returns non-zero if P1 and P2 are equal. */
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203
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204 static int
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205 eq_pointer (const PTR p1, const PTR p2)
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206 {
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207 return p1 == p2;
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208 }
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209
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210
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211 /* The parens around the function names in the next two definitions
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212 are essential in order to prevent macro expansions of the name.
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213 The bodies, however, are expanded as expected, so they are not
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214 recursive definitions. */
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215
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216 /* Return the current size of given hash table. */
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217
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218 #define htab_size(htab) ((htab)->size)
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219
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220 size_t
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221 (htab_size) (htab_t htab)
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222 {
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223 return htab_size (htab);
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224 }
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225
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226 /* Return the current number of elements in given hash table. */
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227
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228 #define htab_elements(htab) ((htab)->n_elements - (htab)->n_deleted)
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229
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230 size_t
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231 (htab_elements) (htab_t htab)
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232 {
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233 return htab_elements (htab);
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234 }
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235
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236 /* Return X % Y. */
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237
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238 static inline hashval_t
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239 htab_mod_1 (hashval_t x, hashval_t y, hashval_t inv, int shift)
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240 {
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241 /* The multiplicative inverses computed above are for 32-bit types, and
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242 requires that we be able to compute a highpart multiply. */
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243 #ifdef UNSIGNED_64BIT_TYPE
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244 __extension__ typedef UNSIGNED_64BIT_TYPE ull;
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245 if (sizeof (hashval_t) * CHAR_BIT <= 32)
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246 {
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247 hashval_t t1, t2, t3, t4, q, r;
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248
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249 t1 = ((ull)x * inv) >> 32;
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250 t2 = x - t1;
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251 t3 = t2 >> 1;
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252 t4 = t1 + t3;
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253 q = t4 >> shift;
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254 r = x - (q * y);
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255
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256 return r;
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257 }
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258 #endif
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259
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260 /* Otherwise just use the native division routines. */
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261 return x % y;
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262 }
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263
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264 /* Compute the primary hash for HASH given HTAB's current size. */
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265
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266 static inline hashval_t
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267 htab_mod (hashval_t hash, htab_t htab)
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268 {
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269 const struct prime_ent *p = &prime_tab[htab->size_prime_index];
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270 return htab_mod_1 (hash, p->prime, p->inv, p->shift);
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271 }
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272
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273 /* Compute the secondary hash for HASH given HTAB's current size. */
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274
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275 static inline hashval_t
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276 htab_mod_m2 (hashval_t hash, htab_t htab)
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277 {
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278 const struct prime_ent *p = &prime_tab[htab->size_prime_index];
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279 return 1 + htab_mod_1 (hash, p->prime - 2, p->inv_m2, p->shift);
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280 }
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281
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282 /* This function creates table with length slightly longer than given
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283 source length. Created hash table is initiated as empty (all the
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284 hash table entries are HTAB_EMPTY_ENTRY). The function returns the
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285 created hash table, or NULL if memory allocation fails. */
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286
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287 htab_t
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288 htab_create_alloc (size_t size, htab_hash hash_f, htab_eq eq_f,
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289 htab_del del_f, htab_alloc alloc_f, htab_free free_f)
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290 {
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291 htab_t result;
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292 unsigned int size_prime_index;
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293
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294 size_prime_index = higher_prime_index (size);
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295 size = prime_tab[size_prime_index].prime;
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296
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297 result = (htab_t) (*alloc_f) (1, sizeof (struct htab));
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298 if (result == NULL)
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299 return NULL;
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300 result->entries = (PTR *) (*alloc_f) (size, sizeof (PTR));
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301 if (result->entries == NULL)
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302 {
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303 if (free_f != NULL)
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304 (*free_f) (result);
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305 return NULL;
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306 }
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307 result->size = size;
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308 result->size_prime_index = size_prime_index;
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309 result->hash_f = hash_f;
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310 result->eq_f = eq_f;
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311 result->del_f = del_f;
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312 result->alloc_f = alloc_f;
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313 result->free_f = free_f;
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314 return result;
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315 }
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316
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317 /* As above, but use the variants of alloc_f and free_f which accept
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318 an extra argument. */
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319
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320 htab_t
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321 htab_create_alloc_ex (size_t size, htab_hash hash_f, htab_eq eq_f,
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322 htab_del del_f, void *alloc_arg,
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323 htab_alloc_with_arg alloc_f,
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324 htab_free_with_arg free_f)
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325 {
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326 htab_t result;
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327 unsigned int size_prime_index;
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328
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329 size_prime_index = higher_prime_index (size);
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330 size = prime_tab[size_prime_index].prime;
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331
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332 result = (htab_t) (*alloc_f) (alloc_arg, 1, sizeof (struct htab));
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333 if (result == NULL)
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334 return NULL;
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335 result->entries = (PTR *) (*alloc_f) (alloc_arg, size, sizeof (PTR));
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336 if (result->entries == NULL)
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337 {
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338 if (free_f != NULL)
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339 (*free_f) (alloc_arg, result);
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340 return NULL;
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341 }
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342 result->size = size;
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343 result->size_prime_index = size_prime_index;
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344 result->hash_f = hash_f;
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345 result->eq_f = eq_f;
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346 result->del_f = del_f;
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347 result->alloc_arg = alloc_arg;
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348 result->alloc_with_arg_f = alloc_f;
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349 result->free_with_arg_f = free_f;
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350 return result;
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351 }
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352
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353 /* Update the function pointers and allocation parameter in the htab_t. */
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354
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355 void
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356 htab_set_functions_ex (htab_t htab, htab_hash hash_f, htab_eq eq_f,
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357 htab_del del_f, PTR alloc_arg,
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358 htab_alloc_with_arg alloc_f, htab_free_with_arg free_f)
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359 {
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360 htab->hash_f = hash_f;
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361 htab->eq_f = eq_f;
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362 htab->del_f = del_f;
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363 htab->alloc_arg = alloc_arg;
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364 htab->alloc_with_arg_f = alloc_f;
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365 htab->free_with_arg_f = free_f;
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366 }
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367
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368 /* These functions exist solely for backward compatibility. */
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369
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370 #undef htab_create
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371 htab_t
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372 htab_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f)
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373 {
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374 return htab_create_alloc (size, hash_f, eq_f, del_f, xcalloc, free);
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375 }
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376
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377 htab_t
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378 htab_try_create (size_t size, htab_hash hash_f, htab_eq eq_f, htab_del del_f)
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379 {
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380 return htab_create_alloc (size, hash_f, eq_f, del_f, calloc, free);
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381 }
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382
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383 /* This function frees all memory allocated for given hash table.
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384 Naturally the hash table must already exist. */
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385
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386 void
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387 htab_delete (htab_t htab)
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388 {
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389 size_t size = htab_size (htab);
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390 PTR *entries = htab->entries;
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391 int i;
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392
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393 if (htab->del_f)
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394 for (i = size - 1; i >= 0; i--)
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395 if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY)
|
|
|
396 (*htab->del_f) (entries[i]);
|
|
|
397
|
|
|
398 if (htab->free_f != NULL)
|
|
|
399 {
|
|
|
400 (*htab->free_f) (entries);
|
|
|
401 (*htab->free_f) (htab);
|
|
|
402 }
|
|
|
403 else if (htab->free_with_arg_f != NULL)
|
|
|
404 {
|
|
|
405 (*htab->free_with_arg_f) (htab->alloc_arg, entries);
|
|
|
406 (*htab->free_with_arg_f) (htab->alloc_arg, htab);
|
|
|
407 }
|
|
|
408 }
|
|
|
409
|
|
|
410 /* This function clears all entries in the given hash table. */
|
|
|
411
|
|
|
412 void
|
|
|
413 htab_empty (htab_t htab)
|
|
|
414 {
|
|
|
415 size_t size = htab_size (htab);
|
|
|
416 PTR *entries = htab->entries;
|
|
|
417 int i;
|
|
|
418
|
|
|
419 if (htab->del_f)
|
|
|
420 for (i = size - 1; i >= 0; i--)
|
|
|
421 if (entries[i] != HTAB_EMPTY_ENTRY && entries[i] != HTAB_DELETED_ENTRY)
|
|
|
422 (*htab->del_f) (entries[i]);
|
|
|
423
|
|
|
424 /* Instead of clearing megabyte, downsize the table. */
|
|
|
425 if (size > 1024*1024 / sizeof (PTR))
|
|
|
426 {
|
|
|
427 int nindex = higher_prime_index (1024 / sizeof (PTR));
|
|
|
428 int nsize = prime_tab[nindex].prime;
|
|
|
429
|
|
|
430 if (htab->free_f != NULL)
|
|
|
431 (*htab->free_f) (htab->entries);
|
|
|
432 else if (htab->free_with_arg_f != NULL)
|
|
|
433 (*htab->free_with_arg_f) (htab->alloc_arg, htab->entries);
|
|
|
434 if (htab->alloc_with_arg_f != NULL)
|
|
|
435 htab->entries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize,
|
|
|
436 sizeof (PTR *));
|
|
|
437 else
|
|
|
438 htab->entries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *));
|
|
|
439 htab->size = nsize;
|
|
|
440 htab->size_prime_index = nindex;
|
|
|
441 }
|
|
|
442 else
|
|
|
443 memset (entries, 0, size * sizeof (PTR));
|
|
|
444 htab->n_deleted = 0;
|
|
|
445 htab->n_elements = 0;
|
|
|
446 }
|
|
|
447
|
|
|
448 /* Similar to htab_find_slot, but without several unwanted side effects:
|
|
|
449 - Does not call htab->eq_f when it finds an existing entry.
|
|
|
450 - Does not change the count of elements/searches/collisions in the
|
|
|
451 hash table.
|
|
|
452 This function also assumes there are no deleted entries in the table.
|
|
|
453 HASH is the hash value for the element to be inserted. */
|
|
|
454
|
|
|
455 static PTR *
|
|
|
456 find_empty_slot_for_expand (htab_t htab, hashval_t hash)
|
|
|
457 {
|
|
|
458 hashval_t index = htab_mod (hash, htab);
|
|
|
459 size_t size = htab_size (htab);
|
|
|
460 PTR *slot = htab->entries + index;
|
|
|
461 hashval_t hash2;
|
|
|
462
|
|
|
463 if (*slot == HTAB_EMPTY_ENTRY)
|
|
|
464 return slot;
|
|
|
465 else if (*slot == HTAB_DELETED_ENTRY)
|
|
|
466 abort ();
|
|
|
467
|
|
|
468 hash2 = htab_mod_m2 (hash, htab);
|
|
|
469 for (;;)
|
|
|
470 {
|
|
|
471 index += hash2;
|
|
|
472 if (index >= size)
|
|
|
473 index -= size;
|
|
|
474
|
|
|
475 slot = htab->entries + index;
|
|
|
476 if (*slot == HTAB_EMPTY_ENTRY)
|
|
|
477 return slot;
|
|
|
478 else if (*slot == HTAB_DELETED_ENTRY)
|
|
|
479 abort ();
|
|
|
480 }
|
|
|
481 }
|
|
|
482
|
|
|
483 /* The following function changes size of memory allocated for the
|
|
|
484 entries and repeatedly inserts the table elements. The occupancy
|
|
|
485 of the table after the call will be about 50%. Naturally the hash
|
|
|
486 table must already exist. Remember also that the place of the
|
|
|
487 table entries is changed. If memory allocation failures are allowed,
|
|
|
488 this function will return zero, indicating that the table could not be
|
|
|
489 expanded. If all goes well, it will return a non-zero value. */
|
|
|
490
|
|
|
491 static int
|
|
|
492 htab_expand (htab_t htab)
|
|
|
493 {
|
|
|
494 PTR *oentries;
|
|
|
495 PTR *olimit;
|
|
|
496 PTR *p;
|
|
|
497 PTR *nentries;
|
|
|
498 size_t nsize, osize, elts;
|
|
|
499 unsigned int oindex, nindex;
|
|
|
500
|
|
|
501 oentries = htab->entries;
|
|
|
502 oindex = htab->size_prime_index;
|
|
|
503 osize = htab->size;
|
|
|
504 olimit = oentries + osize;
|
|
|
505 elts = htab_elements (htab);
|
|
|
506
|
|
|
507 /* Resize only when table after removal of unused elements is either
|
|
|
508 too full or too empty. */
|
|
|
509 if (elts * 2 > osize || (elts * 8 < osize && osize > 32))
|
|
|
510 {
|
|
|
511 nindex = higher_prime_index (elts * 2);
|
|
|
512 nsize = prime_tab[nindex].prime;
|
|
|
513 }
|
|
|
514 else
|
|
|
515 {
|
|
|
516 nindex = oindex;
|
|
|
517 nsize = osize;
|
|
|
518 }
|
|
|
519
|
|
|
520 if (htab->alloc_with_arg_f != NULL)
|
|
|
521 nentries = (PTR *) (*htab->alloc_with_arg_f) (htab->alloc_arg, nsize,
|
|
|
522 sizeof (PTR *));
|
|
|
523 else
|
|
|
524 nentries = (PTR *) (*htab->alloc_f) (nsize, sizeof (PTR *));
|
|
|
525 if (nentries == NULL)
|
|
|
526 return 0;
|
|
|
527 htab->entries = nentries;
|
|
|
528 htab->size = nsize;
|
|
|
529 htab->size_prime_index = nindex;
|
|
|
530 htab->n_elements -= htab->n_deleted;
|
|
|
531 htab->n_deleted = 0;
|
|
|
532
|
|
|
533 p = oentries;
|
|
|
534 do
|
|
|
535 {
|
|
|
536 PTR x = *p;
|
|
|
537
|
|
|
538 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
|
|
|
539 {
|
|
|
540 PTR *q = find_empty_slot_for_expand (htab, (*htab->hash_f) (x));
|
|
|
541
|
|
|
542 *q = x;
|
|
|
543 }
|
|
|
544
|
|
|
545 p++;
|
|
|
546 }
|
|
|
547 while (p < olimit);
|
|
|
548
|
|
|
549 if (htab->free_f != NULL)
|
|
|
550 (*htab->free_f) (oentries);
|
|
|
551 else if (htab->free_with_arg_f != NULL)
|
|
|
552 (*htab->free_with_arg_f) (htab->alloc_arg, oentries);
|
|
|
553 return 1;
|
|
|
554 }
|
|
|
555
|
|
|
556 /* This function searches for a hash table entry equal to the given
|
|
|
557 element. It cannot be used to insert or delete an element. */
|
|
|
558
|
|
|
559 PTR
|
|
|
560 htab_find_with_hash (htab_t htab, const PTR element, hashval_t hash)
|
|
|
561 {
|
|
|
562 hashval_t index, hash2;
|
|
|
563 size_t size;
|
|
|
564 PTR entry;
|
|
|
565
|
|
|
566 htab->searches++;
|
|
|
567 size = htab_size (htab);
|
|
|
568 index = htab_mod (hash, htab);
|
|
|
569
|
|
|
570 entry = htab->entries[index];
|
|
|
571 if (entry == HTAB_EMPTY_ENTRY
|
|
|
572 || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element)))
|
|
|
573 return entry;
|
|
|
574
|
|
|
575 hash2 = htab_mod_m2 (hash, htab);
|
|
|
576 for (;;)
|
|
|
577 {
|
|
|
578 htab->collisions++;
|
|
|
579 index += hash2;
|
|
|
580 if (index >= size)
|
|
|
581 index -= size;
|
|
|
582
|
|
|
583 entry = htab->entries[index];
|
|
|
584 if (entry == HTAB_EMPTY_ENTRY
|
|
|
585 || (entry != HTAB_DELETED_ENTRY && (*htab->eq_f) (entry, element)))
|
|
|
586 return entry;
|
|
|
587 }
|
|
|
588 }
|
|
|
589
|
|
|
590 /* Like htab_find_slot_with_hash, but compute the hash value from the
|
|
|
591 element. */
|
|
|
592
|
|
|
593 PTR
|
|
|
594 htab_find (htab_t htab, const PTR element)
|
|
|
595 {
|
|
|
596 return htab_find_with_hash (htab, element, (*htab->hash_f) (element));
|
|
|
597 }
|
|
|
598
|
|
|
599 /* This function searches for a hash table slot containing an entry
|
|
|
600 equal to the given element. To delete an entry, call this with
|
|
|
601 insert=NO_INSERT, then call htab_clear_slot on the slot returned
|
|
|
602 (possibly after doing some checks). To insert an entry, call this
|
|
|
603 with insert=INSERT, then write the value you want into the returned
|
|
|
604 slot. When inserting an entry, NULL may be returned if memory
|
|
|
605 allocation fails. */
|
|
|
606
|
|
|
607 PTR *
|
|
|
608 htab_find_slot_with_hash (htab_t htab, const PTR element,
|
|
|
609 hashval_t hash, enum insert_option insert)
|
|
|
610 {
|
|
|
611 PTR *first_deleted_slot;
|
|
|
612 hashval_t index, hash2;
|
|
|
613 size_t size;
|
|
|
614 PTR entry;
|
|
|
615
|
|
|
616 size = htab_size (htab);
|
|
|
617 if (insert == INSERT && size * 3 <= htab->n_elements * 4)
|
|
|
618 {
|
|
|
619 if (htab_expand (htab) == 0)
|
|
|
620 return NULL;
|
|
|
621 size = htab_size (htab);
|
|
|
622 }
|
|
|
623
|
|
|
624 index = htab_mod (hash, htab);
|
|
|
625
|
|
|
626 htab->searches++;
|
|
|
627 first_deleted_slot = NULL;
|
|
|
628
|
|
|
629 entry = htab->entries[index];
|
|
|
630 if (entry == HTAB_EMPTY_ENTRY)
|
|
|
631 goto empty_entry;
|
|
|
632 else if (entry == HTAB_DELETED_ENTRY)
|
|
|
633 first_deleted_slot = &htab->entries[index];
|
|
|
634 else if ((*htab->eq_f) (entry, element))
|
|
|
635 return &htab->entries[index];
|
|
|
636
|
|
|
637 hash2 = htab_mod_m2 (hash, htab);
|
|
|
638 for (;;)
|
|
|
639 {
|
|
|
640 htab->collisions++;
|
|
|
641 index += hash2;
|
|
|
642 if (index >= size)
|
|
|
643 index -= size;
|
|
|
644
|
|
|
645 entry = htab->entries[index];
|
|
|
646 if (entry == HTAB_EMPTY_ENTRY)
|
|
|
647 goto empty_entry;
|
|
|
648 else if (entry == HTAB_DELETED_ENTRY)
|
|
|
649 {
|
|
|
650 if (!first_deleted_slot)
|
|
|
651 first_deleted_slot = &htab->entries[index];
|
|
|
652 }
|
|
|
653 else if ((*htab->eq_f) (entry, element))
|
|
|
654 return &htab->entries[index];
|
|
|
655 }
|
|
|
656
|
|
|
657 empty_entry:
|
|
|
658 if (insert == NO_INSERT)
|
|
|
659 return NULL;
|
|
|
660
|
|
|
661 if (first_deleted_slot)
|
|
|
662 {
|
|
|
663 htab->n_deleted--;
|
|
|
664 *first_deleted_slot = HTAB_EMPTY_ENTRY;
|
|
|
665 return first_deleted_slot;
|
|
|
666 }
|
|
|
667
|
|
|
668 htab->n_elements++;
|
|
|
669 return &htab->entries[index];
|
|
|
670 }
|
|
|
671
|
|
|
672 /* Like htab_find_slot_with_hash, but compute the hash value from the
|
|
|
673 element. */
|
|
|
674
|
|
|
675 PTR *
|
|
|
676 htab_find_slot (htab_t htab, const PTR element, enum insert_option insert)
|
|
|
677 {
|
|
|
678 return htab_find_slot_with_hash (htab, element, (*htab->hash_f) (element),
|
|
|
679 insert);
|
|
|
680 }
|
|
|
681
|
|
|
682 /* This function deletes an element with the given value from hash
|
|
|
683 table (the hash is computed from the element). If there is no matching
|
|
|
684 element in the hash table, this function does nothing. */
|
|
|
685
|
|
|
686 void
|
|
|
687 htab_remove_elt (htab_t htab, PTR element)
|
|
|
688 {
|
|
|
689 htab_remove_elt_with_hash (htab, element, (*htab->hash_f) (element));
|
|
|
690 }
|
|
|
691
|
|
|
692
|
|
|
693 /* This function deletes an element with the given value from hash
|
|
|
694 table. If there is no matching element in the hash table, this
|
|
|
695 function does nothing. */
|
|
|
696
|
|
|
697 void
|
|
|
698 htab_remove_elt_with_hash (htab_t htab, PTR element, hashval_t hash)
|
|
|
699 {
|
|
|
700 PTR *slot;
|
|
|
701
|
|
|
702 slot = htab_find_slot_with_hash (htab, element, hash, NO_INSERT);
|
|
|
703 if (*slot == HTAB_EMPTY_ENTRY)
|
|
|
704 return;
|
|
|
705
|
|
|
706 if (htab->del_f)
|
|
|
707 (*htab->del_f) (*slot);
|
|
|
708
|
|
|
709 *slot = HTAB_DELETED_ENTRY;
|
|
|
710 htab->n_deleted++;
|
|
|
711 }
|
|
|
712
|
|
|
713 /* This function clears a specified slot in a hash table. It is
|
|
|
714 useful when you've already done the lookup and don't want to do it
|
|
|
715 again. */
|
|
|
716
|
|
|
717 void
|
|
|
718 htab_clear_slot (htab_t htab, PTR *slot)
|
|
|
719 {
|
|
|
720 if (slot < htab->entries || slot >= htab->entries + htab_size (htab)
|
|
|
721 || *slot == HTAB_EMPTY_ENTRY || *slot == HTAB_DELETED_ENTRY)
|
|
|
722 abort ();
|
|
|
723
|
|
|
724 if (htab->del_f)
|
|
|
725 (*htab->del_f) (*slot);
|
|
|
726
|
|
|
727 *slot = HTAB_DELETED_ENTRY;
|
|
|
728 htab->n_deleted++;
|
|
|
729 }
|
|
|
730
|
|
|
731 /* This function scans over the entire hash table calling
|
|
|
732 CALLBACK for each live entry. If CALLBACK returns false,
|
|
|
733 the iteration stops. INFO is passed as CALLBACK's second
|
|
|
734 argument. */
|
|
|
735
|
|
|
736 void
|
|
|
737 htab_traverse_noresize (htab_t htab, htab_trav callback, PTR info)
|
|
|
738 {
|
|
|
739 PTR *slot;
|
|
|
740 PTR *limit;
|
|
|
741
|
|
|
742 slot = htab->entries;
|
|
|
743 limit = slot + htab_size (htab);
|
|
|
744
|
|
|
745 do
|
|
|
746 {
|
|
|
747 PTR x = *slot;
|
|
|
748
|
|
|
749 if (x != HTAB_EMPTY_ENTRY && x != HTAB_DELETED_ENTRY)
|
|
|
750 if (!(*callback) (slot, info))
|
|
|
751 break;
|
|
|
752 }
|
|
|
753 while (++slot < limit);
|
|
|
754 }
|
|
|
755
|
|
|
756 /* Like htab_traverse_noresize, but does resize the table when it is
|
|
|
757 too empty to improve effectivity of subsequent calls. */
|
|
|
758
|
|
|
759 void
|
|
|
760 htab_traverse (htab_t htab, htab_trav callback, PTR info)
|
|
|
761 {
|
|
|
762 if (htab_elements (htab) * 8 < htab_size (htab))
|
|
|
763 htab_expand (htab);
|
|
|
764
|
|
|
765 htab_traverse_noresize (htab, callback, info);
|
|
|
766 }
|
|
|
767
|
|
|
768 /* Return the fraction of fixed collisions during all work with given
|
|
|
769 hash table. */
|
|
|
770
|
|
|
771 double
|
|
|
772 htab_collisions (htab_t htab)
|
|
|
773 {
|
|
|
774 if (htab->searches == 0)
|
|
|
775 return 0.0;
|
|
|
776
|
|
|
777 return (double) htab->collisions / (double) htab->searches;
|
|
|
778 }
|
|
|
779
|
|
|
780 /* Hash P as a null-terminated string.
|
|
|
781
|
|
|
782 Copied from gcc/hashtable.c. Zack had the following to say with respect
|
|
|
783 to applicability, though note that unlike hashtable.c, this hash table
|
|
|
784 implementation re-hashes rather than chain buckets.
|
|
|
785
|
|
|
786 http://gcc.gnu.org/ml/gcc-patches/2001-08/msg01021.html
|
|
|
787 From: Zack Weinberg <zackw@panix.com>
|
|
|
788 Date: Fri, 17 Aug 2001 02:15:56 -0400
|
|
|
789
|
|
|
790 I got it by extracting all the identifiers from all the source code
|
|
|
791 I had lying around in mid-1999, and testing many recurrences of
|
|
|
792 the form "H_n = H_{n-1} * K + c_n * L + M" where K, L, M were either
|
|
|
793 prime numbers or the appropriate identity. This was the best one.
|
|
|
794 I don't remember exactly what constituted "best", except I was
|
|
|
795 looking at bucket-length distributions mostly.
|
|
|
796
|
|
|
797 So it should be very good at hashing identifiers, but might not be
|
|
|
798 as good at arbitrary strings.
|
|
|
799
|
|
|
800 I'll add that it thoroughly trounces the hash functions recommended
|
|
|
801 for this use at http://burtleburtle.net/bob/hash/index.html, both
|
|
|
802 on speed and bucket distribution. I haven't tried it against the
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|
803 function they just started using for Perl's hashes. */
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|
|
804
|
|
|
805 hashval_t
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|
|
806 htab_hash_string (const PTR p)
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|
807 {
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|
|
808 const unsigned char *str = (const unsigned char *) p;
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|
|
809 hashval_t r = 0;
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|
|
810 unsigned char c;
|
|
|
811
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|
812 while ((c = *str++) != 0)
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|
813 r = r * 67 + c - 113;
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|
|
814
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|
|
815 return r;
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|
|
816 }
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|
|
817
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|
|
818 /* DERIVED FROM:
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|
|
819 --------------------------------------------------------------------
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|
820 lookup2.c, by Bob Jenkins, December 1996, Public Domain.
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|
821 hash(), hash2(), hash3, and mix() are externally useful functions.
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|
822 Routines to test the hash are included if SELF_TEST is defined.
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|
|
823 You can use this free for any purpose. It has no warranty.
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|
|
824 --------------------------------------------------------------------
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|
825 */
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|
826
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|
827 /*
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|
|
828 --------------------------------------------------------------------
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|
|
829 mix -- mix 3 32-bit values reversibly.
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|
|
830 For every delta with one or two bit set, and the deltas of all three
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|
831 high bits or all three low bits, whether the original value of a,b,c
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|
|
832 is almost all zero or is uniformly distributed,
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|
833 * If mix() is run forward or backward, at least 32 bits in a,b,c
|
|
|
834 have at least 1/4 probability of changing.
|
|
|
835 * If mix() is run forward, every bit of c will change between 1/3 and
|
|
|
836 2/3 of the time. (Well, 22/100 and 78/100 for some 2-bit deltas.)
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|
|
837 mix() was built out of 36 single-cycle latency instructions in a
|
|
|
838 structure that could supported 2x parallelism, like so:
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|
|
839 a -= b;
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|
840 a -= c; x = (c>>13);
|
|
|
841 b -= c; a ^= x;
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|
|
842 b -= a; x = (a<<8);
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|
|
843 c -= a; b ^= x;
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|
|
844 c -= b; x = (b>>13);
|
|
|
845 ...
|
|
|
846 Unfortunately, superscalar Pentiums and Sparcs can't take advantage
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|
|
847 of that parallelism. They've also turned some of those single-cycle
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|
|
848 latency instructions into multi-cycle latency instructions. Still,
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|
|
849 this is the fastest good hash I could find. There were about 2^^68
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|
850 to choose from. I only looked at a billion or so.
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|
|
851 --------------------------------------------------------------------
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|
852 */
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|
|
853 /* same, but slower, works on systems that might have 8 byte hashval_t's */
|
|
|
854 #define mix(a,b,c) \
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|
855 { \
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|
|
856 a -= b; a -= c; a ^= (c>>13); \
|
|
|
857 b -= c; b -= a; b ^= (a<< 8); \
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|
|
858 c -= a; c -= b; c ^= ((b&0xffffffff)>>13); \
|
|
|
859 a -= b; a -= c; a ^= ((c&0xffffffff)>>12); \
|
|
|
860 b -= c; b -= a; b = (b ^ (a<<16)) & 0xffffffff; \
|
|
|
861 c -= a; c -= b; c = (c ^ (b>> 5)) & 0xffffffff; \
|
|
|
862 a -= b; a -= c; a = (a ^ (c>> 3)) & 0xffffffff; \
|
|
|
863 b -= c; b -= a; b = (b ^ (a<<10)) & 0xffffffff; \
|
|
|
864 c -= a; c -= b; c = (c ^ (b>>15)) & 0xffffffff; \
|
|
|
865 }
|
|
|
866
|
|
|
867 /*
|
|
|
868 --------------------------------------------------------------------
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|
|
869 hash() -- hash a variable-length key into a 32-bit value
|
|
|
870 k : the key (the unaligned variable-length array of bytes)
|
|
|
871 len : the length of the key, counting by bytes
|
|
|
872 level : can be any 4-byte value
|
|
|
873 Returns a 32-bit value. Every bit of the key affects every bit of
|
|
|
874 the return value. Every 1-bit and 2-bit delta achieves avalanche.
|
|
|
875 About 36+6len instructions.
|
|
|
876
|
|
|
877 The best hash table sizes are powers of 2. There is no need to do
|
|
|
878 mod a prime (mod is sooo slow!). If you need less than 32 bits,
|
|
|
879 use a bitmask. For example, if you need only 10 bits, do
|
|
|
880 h = (h & hashmask(10));
|
|
|
881 In which case, the hash table should have hashsize(10) elements.
|
|
|
882
|
|
|
883 If you are hashing n strings (ub1 **)k, do it like this:
|
|
|
884 for (i=0, h=0; i<n; ++i) h = hash( k[i], len[i], h);
|
|
|
885
|
|
|
886 By Bob Jenkins, 1996. bob_jenkins@burtleburtle.net. You may use this
|
|
|
887 code any way you wish, private, educational, or commercial. It's free.
|
|
|
888
|
|
|
889 See http://burtleburtle.net/bob/hash/evahash.html
|
|
|
890 Use for hash table lookup, or anything where one collision in 2^32 is
|
|
|
891 acceptable. Do NOT use for cryptographic purposes.
|
|
|
892 --------------------------------------------------------------------
|
|
|
893 */
|
|
|
894
|
|
|
895 hashval_t
|
|
|
896 iterative_hash (const PTR k_in /* the key */,
|
|
|
897 register size_t length /* the length of the key */,
|
|
|
898 register hashval_t initval /* the previous hash, or
|
|
|
899 an arbitrary value */)
|
|
|
900 {
|
|
|
901 register const unsigned char *k = (const unsigned char *)k_in;
|
|
|
902 register hashval_t a,b,c,len;
|
|
|
903
|
|
|
904 /* Set up the internal state */
|
|
|
905 len = length;
|
|
|
906 a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
|
|
|
907 c = initval; /* the previous hash value */
|
|
|
908
|
|
|
909 /*---------------------------------------- handle most of the key */
|
|
|
910 #ifndef WORDS_BIGENDIAN
|
|
|
911 /* On a little-endian machine, if the data is 4-byte aligned we can hash
|
|
|
912 by word for better speed. This gives nondeterministic results on
|
|
|
913 big-endian machines. */
|
|
|
914 if (sizeof (hashval_t) == 4 && (((size_t)k)&3) == 0)
|
|
|
915 while (len >= 12) /* aligned */
|
|
|
916 {
|
|
|
917 a += *(hashval_t *)(k+0);
|
|
|
918 b += *(hashval_t *)(k+4);
|
|
|
919 c += *(hashval_t *)(k+8);
|
|
|
920 mix(a,b,c);
|
|
|
921 k += 12; len -= 12;
|
|
|
922 }
|
|
|
923 else /* unaligned */
|
|
|
924 #endif
|
|
|
925 while (len >= 12)
|
|
|
926 {
|
|
|
927 a += (k[0] +((hashval_t)k[1]<<8) +((hashval_t)k[2]<<16) +((hashval_t)k[3]<<24));
|
|
|
928 b += (k[4] +((hashval_t)k[5]<<8) +((hashval_t)k[6]<<16) +((hashval_t)k[7]<<24));
|
|
|
929 c += (k[8] +((hashval_t)k[9]<<8) +((hashval_t)k[10]<<16)+((hashval_t)k[11]<<24));
|
|
|
930 mix(a,b,c);
|
|
|
931 k += 12; len -= 12;
|
|
|
932 }
|
|
|
933
|
|
|
934 /*------------------------------------- handle the last 11 bytes */
|
|
|
935 c += length;
|
|
|
936 switch(len) /* all the case statements fall through */
|
|
|
937 {
|
|
|
938 case 11: c+=((hashval_t)k[10]<<24);
|
|
|
939 case 10: c+=((hashval_t)k[9]<<16);
|
|
|
940 case 9 : c+=((hashval_t)k[8]<<8);
|
|
|
941 /* the first byte of c is reserved for the length */
|
|
|
942 case 8 : b+=((hashval_t)k[7]<<24);
|
|
|
943 case 7 : b+=((hashval_t)k[6]<<16);
|
|
|
944 case 6 : b+=((hashval_t)k[5]<<8);
|
|
|
945 case 5 : b+=k[4];
|
|
|
946 case 4 : a+=((hashval_t)k[3]<<24);
|
|
|
947 case 3 : a+=((hashval_t)k[2]<<16);
|
|
|
948 case 2 : a+=((hashval_t)k[1]<<8);
|
|
|
949 case 1 : a+=k[0];
|
|
|
950 /* case 0: nothing left to add */
|
|
|
951 }
|
|
|
952 mix(a,b,c);
|
|
|
953 /*-------------------------------------------- report the result */
|
|
|
954 return c;
|
|
|
955 }
|
