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1 /* Set operations on pointers
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2 Copyright (C) 2004, 2006, 2007 Free Software Foundation, Inc.
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3
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4 This file is part of GCC.
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5
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6 GCC is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 3, or (at your option)
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9 any later version.
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10
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11 GCC is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with GCC; see the file COPYING3. If not see
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18 <http://www.gnu.org/licenses/>. */
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19
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20 #include "config.h"
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21 #include "system.h"
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22 #include "pointer-set.h"
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23
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24 /* A pointer set is represented as a simple open-addressing hash
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25 table. Simplifications: The hash code is based on the value of the
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26 pointer, not what it points to. The number of buckets is always a
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27 power of 2. Null pointers are a reserved value. Deletion is not
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28 supported (yet). There is no mechanism for user control of hash
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29 function, equality comparison, initial size, or resizing policy. */
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30
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31 struct pointer_set_t
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32 {
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33 size_t log_slots;
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34 size_t n_slots; /* n_slots = 2^log_slots */
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35 size_t n_elements;
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36
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37 const void **slots;
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38 };
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39
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40 /* Use the multiplicative method, as described in Knuth 6.4, to obtain
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41 a hash code for P in the range [0, MAX). MAX == 2^LOGMAX.
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42
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43 Summary of this method: Multiply p by some number A that's
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44 relatively prime to 2^sizeof(size_t). The result is two words.
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45 Discard the most significant word, and return the most significant
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46 N bits of the least significant word. As suggested by Knuth, our
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47 choice for A is the integer part of (ULONG_MAX + 1.0) / phi, where phi
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48 is the golden ratio.
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49
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50 We don't need to do anything special for full-width multiplication
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51 because we're only interested in the least significant word of the
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52 product, and unsigned arithmetic in C is modulo the word size. */
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53
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54 static inline size_t
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55 hash1 (const void *p, unsigned long max, unsigned long logmax)
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56 {
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57 #if HOST_BITS_PER_LONG == 32
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58 const unsigned long A = 0x9e3779b9u;
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59 #elif HOST_BITS_PER_LONG == 64
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60 const unsigned long A = 0x9e3779b97f4a7c16ul;
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61 #else
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62 const unsigned long A
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63 = (ULONG_MAX + 1.0L) * 0.6180339887498948482045868343656381177203L;
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64 #endif
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65 const unsigned long shift = HOST_BITS_PER_LONG - logmax;
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66
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67 return ((A * (unsigned long) p) >> shift) & (max - 1);
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68 }
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69
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70 /* Allocate an empty pointer set. */
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71 struct pointer_set_t *
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72 pointer_set_create (void)
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73 {
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74 struct pointer_set_t *result = XNEW (struct pointer_set_t);
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75
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76 result->n_elements = 0;
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77 result->log_slots = 8;
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78 result->n_slots = (size_t) 1 << result->log_slots;
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79
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80 result->slots = XCNEWVEC (const void *, result->n_slots);
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81 return result;
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82 }
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83
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84 /* Reclaims all memory associated with PSET. */
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85 void
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86 pointer_set_destroy (struct pointer_set_t *pset)
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87 {
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88 XDELETEVEC (pset->slots);
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89 XDELETE (pset);
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90 }
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91
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92 /* Returns nonzero if PSET contains P. P must be nonnull.
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93
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94 Collisions are resolved by linear probing. */
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95 int
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96 pointer_set_contains (const struct pointer_set_t *pset, const void *p)
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97 {
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98 size_t n = hash1 (p, pset->n_slots, pset->log_slots);
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99
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100 while (true)
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101 {
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102 if (pset->slots[n] == p)
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103 return 1;
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104 else if (pset->slots[n] == 0)
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105 return 0;
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106 else
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107 {
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108 ++n;
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109 if (n == pset->n_slots)
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110 n = 0;
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111 }
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112 }
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113 }
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114
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115 /* Subroutine of pointer_set_insert. Return the insertion slot for P into
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116 an empty element of SLOTS, an array of length N_SLOTS. */
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117 static inline size_t
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118 insert_aux (const void *p, const void **slots, size_t n_slots, size_t log_slots)
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119 {
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120 size_t n = hash1 (p, n_slots, log_slots);
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121 while (true)
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122 {
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123 if (slots[n] == p || slots[n] == 0)
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124 return n;
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125 else
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126 {
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127 ++n;
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128 if (n == n_slots)
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129 n = 0;
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130 }
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131 }
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132 }
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133
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134 /* Inserts P into PSET if it wasn't already there. Returns nonzero
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135 if it was already there. P must be nonnull. */
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136 int
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137 pointer_set_insert (struct pointer_set_t *pset, const void *p)
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138 {
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139 size_t n;
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140
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141 /* For simplicity, expand the set even if P is already there. This can be
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142 superfluous but can happen at most once. */
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143 if (pset->n_elements > pset->n_slots / 4)
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144 {
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145 size_t new_log_slots = pset->log_slots + 1;
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146 size_t new_n_slots = pset->n_slots * 2;
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147 const void **new_slots = XCNEWVEC (const void *, new_n_slots);
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148 size_t i;
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149
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150 for (i = 0; i < pset->n_slots; ++i)
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151 {
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152 const void *value = pset->slots[i];
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153 n = insert_aux (value, new_slots, new_n_slots, new_log_slots);
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154 new_slots[n] = value;
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155 }
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156
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157 XDELETEVEC (pset->slots);
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158 pset->n_slots = new_n_slots;
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159 pset->log_slots = new_log_slots;
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160 pset->slots = new_slots;
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161 }
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162
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163 n = insert_aux (p, pset->slots, pset->n_slots, pset->log_slots);
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164 if (pset->slots[n])
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165 return 1;
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166
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167 pset->slots[n] = p;
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168 ++pset->n_elements;
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169 return 0;
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170 }
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171
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172 /* Pass each pointer in PSET to the function in FN, together with the fixed
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173 parameter DATA. If FN returns false, the iteration stops. */
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174
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175 void pointer_set_traverse (const struct pointer_set_t *pset,
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176 bool (*fn) (const void *, void *), void *data)
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177 {
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178 size_t i;
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179 for (i = 0; i < pset->n_slots; ++i)
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180 if (pset->slots[i] && !fn (pset->slots[i], data))
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181 break;
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182 }
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183
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184
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185 /* A pointer map is represented the same way as a pointer_set, so
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186 the hash code is based on the address of the key, rather than
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187 its contents. Null keys are a reserved value. Deletion is not
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188 supported (yet). There is no mechanism for user control of hash
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189 function, equality comparison, initial size, or resizing policy. */
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190
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191 struct pointer_map_t
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192 {
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193 size_t log_slots;
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194 size_t n_slots; /* n_slots = 2^log_slots */
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195 size_t n_elements;
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196
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197 const void **keys;
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198 void **values;
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199 };
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200
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201 /* Allocate an empty pointer map. */
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202 struct pointer_map_t *
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203 pointer_map_create (void)
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204 {
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205 struct pointer_map_t *result = XNEW (struct pointer_map_t);
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206
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207 result->n_elements = 0;
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208 result->log_slots = 8;
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209 result->n_slots = (size_t) 1 << result->log_slots;
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210
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211 result->keys = XCNEWVEC (const void *, result->n_slots);
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212 result->values = XCNEWVEC (void *, result->n_slots);
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213 return result;
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214 }
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215
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216 /* Reclaims all memory associated with PMAP. */
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217 void pointer_map_destroy (struct pointer_map_t *pmap)
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218 {
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219 XDELETEVEC (pmap->keys);
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220 XDELETEVEC (pmap->values);
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221 XDELETE (pmap);
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222 }
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223
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224 /* Returns a pointer to the value to which P maps, if PMAP contains P. P
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225 must be nonnull. Return NULL if PMAP does not contain P.
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226
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227 Collisions are resolved by linear probing. */
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228 void **
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229 pointer_map_contains (const struct pointer_map_t *pmap, const void *p)
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230 {
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231 size_t n = hash1 (p, pmap->n_slots, pmap->log_slots);
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232
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233 while (true)
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234 {
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235 if (pmap->keys[n] == p)
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236 return &pmap->values[n];
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237 else if (pmap->keys[n] == 0)
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238 return NULL;
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239 else
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240 {
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241 ++n;
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242 if (n == pmap->n_slots)
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243 n = 0;
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244 }
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245 }
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246 }
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247
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248 /* Inserts P into PMAP if it wasn't already there. Returns a pointer
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249 to the value. P must be nonnull. */
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250 void **
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251 pointer_map_insert (struct pointer_map_t *pmap, const void *p)
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252 {
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253 size_t n;
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254
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255 /* For simplicity, expand the map even if P is already there. This can be
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256 superfluous but can happen at most once. */
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257 if (pmap->n_elements > pmap->n_slots / 4)
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258 {
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259 size_t new_log_slots = pmap->log_slots + 1;
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260 size_t new_n_slots = pmap->n_slots * 2;
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261 const void **new_keys = XCNEWVEC (const void *, new_n_slots);
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262 void **new_values = XCNEWVEC (void *, new_n_slots);
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263 size_t i;
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264
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265 for (i = 0; i < pmap->n_slots; ++i)
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266 if (pmap->keys[i])
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267 {
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268 const void *key = pmap->keys[i];
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269 n = insert_aux (key, new_keys, new_n_slots, new_log_slots);
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270 new_keys[n] = key;
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271 new_values[n] = pmap->values[i];
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272 }
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273
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274 XDELETEVEC (pmap->keys);
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275 XDELETEVEC (pmap->values);
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276 pmap->n_slots = new_n_slots;
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277 pmap->log_slots = new_log_slots;
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278 pmap->keys = new_keys;
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279 pmap->values = new_values;
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280 }
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281
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282 n = insert_aux (p, pmap->keys, pmap->n_slots, pmap->log_slots);
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283 if (!pmap->keys[n])
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284 {
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285 ++pmap->n_elements;
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286 pmap->keys[n] = p;
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287 }
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288
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289 return &pmap->values[n];
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290 }
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291
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292 /* Pass each pointer in PMAP to the function in FN, together with the pointer
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293 to the value and the fixed parameter DATA. If FN returns false, the
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294 iteration stops. */
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295
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296 void pointer_map_traverse (const struct pointer_map_t *pmap,
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297 bool (*fn) (const void *, void **, void *), void *data)
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298 {
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299 size_t i;
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300 for (i = 0; i < pmap->n_slots; ++i)
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301 if (pmap->keys[i] && !fn (pmap->keys[i], &pmap->values[i], data))
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302 break;
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303 }
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