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1 /* Copyright (C) 2012-2020 Free Software Foundation, Inc.
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111
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2
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3 This file is part of GCC.
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4
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5 GCC is free software; you can redistribute it and/or modify
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6 it under the terms of the GNU General Public License as published by
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7 the Free Software Foundation; either version 3, or (at your option)
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8 any later version.
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9
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10 GCC is distributed in the hope that it will be useful,
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11 but WITHOUT ANY WARRANTY; without even the implied warranty of
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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13 GNU General Public License for more details.
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14
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15 Under Section 7 of GPL version 3, you are granted additional
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16 permissions described in the GCC Runtime Library Exception, version
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17 3.1, as published by the Free Software Foundation.
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18
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19 You should have received a copy of the GNU General Public License and
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20 a copy of the GCC Runtime Library Exception along with this program;
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21 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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22 <http://www.gnu.org/licenses/>. */
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23
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24 #ifndef _VTV_MAP_H
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25 #define _VTV_MAP_H 1
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26
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27 #include <string.h>
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28
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29 #ifdef __MINGW32__
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30 #include <stdint.h>
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31 #include "vtv_utils.h"
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32 #else
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33 #include <vtv_utils.h>
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34 #endif
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35
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36 inline uint64_t
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37 load8bytes (const void *p)
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38 {
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39 uint64_t result;
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40 memcpy (&result, p, 8);
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41 return result;
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42 }
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43
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44 /* Insert_only_hash_map maps keys to values. The implementation is a
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45 basic hash table with open addressing. The keys are not "owned" by
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46 the table; it only stores pointers to keys. The key type is
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47 specified below (see insert_only_hash_map::key_type) and is,
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48 roughly speaking, a string of any length with the string length and
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49 a hash code stored at the front. The code here does not compute
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50 any hash codes, but rather uses what's given. */
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51
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52 template<typename T, typename Alloc>
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53 class insert_only_hash_map
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54 {
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55 public:
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56 typedef size_t size_type;
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57 typedef T value_type;
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58 typedef Alloc alloc_type;
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59 enum { min_capacity = 4 };
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60 #if HASHMAP_STATS
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61 enum { stats = true };
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62 #else
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63 enum { stats = false };
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64 #endif
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65
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66 /* Keys are a byte string (up to 2^32 - 1 long) plus a uint32_t
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67 that's used as a hash code. The latter can encode arbitrary
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68 information at the client's discretion, so, e.g., multiple keys
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69 that are the same string still "differ" if the hash codes differ.
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70 Keys are equal if the first 8 bytes are equal and the next n
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71 bytes are equal. */
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72 struct key_type
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73 {
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74 uint32_t n;
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75 uint32_t hash;
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76 char bytes[0];
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77
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78 bool
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79 equals (const key_type *k) const;
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80 };
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81
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82 /* Create an empty map with a reasonable number of buckets for the
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83 expected size. Returns NULL if the allocator fails. */
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84
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85 static insert_only_hash_map *
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86 create (size_type expected_size);
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87
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88 /* The opposite of create(). Free the memory for the given map. */
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89
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90 static void
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91 destroy (insert_only_hash_map *m)
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92 { Alloc().dealloc (m, m->size_in_bytes_); }
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93
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94 /* Return a map identical to this except that *k is mapped to v.
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95 Typcially it's done by modifying this in place, but if a resize
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96 is necessary then this is deallocated and a new map is returned.
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97 Requires k to be non-NULL. Does nothing and returns NULL if the
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98 allocator fails. */
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99
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100 insert_only_hash_map*
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101 put (const key_type *k, const value_type &v)
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102 { return this->put_internal (k, v, false); }
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103
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104 /* If *k is a key in this then set *v to point to the corresponding
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105 value. Otherwise, do the equivalent of insert(k, value_type())
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106 and, if that succeeds, set *v to point to the inserted value.
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107 Requires k to be non-NULL. Does nothing and returns NULL if the
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108 allocator fails. Typically returns this, but will return a new
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109 insert_only_hash_map if a resize occurs. If the return value is
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110 non-NULL, *v is set and it's valid until a resize of the map that
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111 is the return value. */
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112
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113 insert_only_hash_map *
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114 find_or_add_key (const key_type *k, value_type **v);
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115
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116 /* Get the value corresponding to *k. Returns NULL if there is
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117 none. Requires k to be non-NULL. The return value is valid
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118 until any resize. */
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119 const value_type *get (const key_type *k) const;
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120
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121 size_type
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122 size () const
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123 { return num_entries_; }
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124
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125 bool
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126 empty () const
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127 { return this->size () == 0; }
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128
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129 size_type
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130 bucket_count () const
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131 { return num_buckets_; }
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132
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133 private:
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134 typedef std::pair <const key_type *, value_type> bucket_type;
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135
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136 insert_only_hash_map *put_internal (const key_type *, const value_type &,
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137 bool);
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138
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139 /* This function determines when to resize the table. */
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140 bool
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141 is_too_full (size_type entries) const
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142 { return entries > (this->bucket_count () * 0.7); }
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143
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144 /* Return a copy with double the number of buckets. Returns NULL if
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145 the allocator fails. Otherwise, calls destroy (this). */
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146 insert_only_hash_map *destructive_copy ();
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147
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148 /* Must be a power of 2 not less than min_capacity. */
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149 size_type num_buckets_;
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150 size_type num_entries_;
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151 size_type size_in_bytes_;
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152 bucket_type buckets[0]; /* Actual array size is num_buckets. */
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153 };
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154
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155 template <typename T, typename Alloc>
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156 insert_only_hash_map <T, Alloc> *
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157 insert_only_hash_map <T, Alloc>::create (size_type expected_size)
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158 {
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159 size_t cap = min_capacity;
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160 while (expected_size >= cap)
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161 {
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162 cap *= 2;
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163 }
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164 size_t size_in_bytes = sizeof (insert_only_hash_map <T, Alloc>)
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165 + cap * sizeof (bucket_type);
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166 insert_only_hash_map <T, Alloc>* result =
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167 static_cast <insert_only_hash_map <T, Alloc>*> (Alloc ()
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168 .alloc (size_in_bytes));
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169 if (result != NULL)
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170 {
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171 result->size_in_bytes_ = size_in_bytes;
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172 result->num_buckets_ = cap;
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173 result->num_entries_ = 0;
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174 memset (result->buckets, 0, cap * sizeof (bucket_type));
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175 }
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176 return result;
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177 }
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178
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179 template <typename T, typename Alloc>
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180 insert_only_hash_map <T, Alloc>*
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181 insert_only_hash_map <T, Alloc>::destructive_copy ()
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182 {
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183 insert_only_hash_map* copy = create (this->bucket_count ());
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184 if (copy == NULL)
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185 return NULL;
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186 VTV_DEBUG_ASSERT (copy->bucket_count () == 2 * this->bucket_count ());
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187 for (size_type i = 0; i < this->bucket_count (); i++)
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188 if (this->buckets[i].first != NULL)
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189 copy->put_internal (this->buckets[i].first, this->buckets[i].second,
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190 true);
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191 VTV_DEBUG_ASSERT (copy->size () == this->size ());
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192 destroy (this);
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193 return copy;
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194 }
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195
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196 template <typename T, typename Alloc>
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197 insert_only_hash_map <T, Alloc>*
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198 insert_only_hash_map <T, Alloc>::find_or_add_key (const key_type *k,
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199 value_type **v)
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200 {
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201 /* Table size is always a power of 2. */
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202 const size_type mask = this->bucket_count () - 1;
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203 size_type bucket_index = k->hash & mask;
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204 size_type step = 1;
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205 for (;;)
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206 {
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207 bucket_type &bucket = this->buckets[bucket_index];
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208 if (bucket.first == NULL)
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209 {
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210 /* Key was not present. */
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211 if (this->is_too_full (this->size () + 1))
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212 {
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213 insert_only_hash_map <T, Alloc>* result =
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214 this->destructive_copy ();
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215 return result == NULL
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216 ? NULL
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217 : result->find_or_add_key (k, v);
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218 }
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219 else
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220 {
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221 bucket.first = k;
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222 bucket.second = T ();
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223 this->num_entries_++;
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224 *v = &bucket.second;
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225 return this;
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226 }
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227 }
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228 else if (bucket.first->equals (k))
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229 {
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230 /* Key was present. */
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231 *v = &bucket.second;
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232 return this;
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233 }
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234 else
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235 bucket_index = (bucket_index + step++) & mask;
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236 }
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237 }
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238
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239 template <typename T, typename Alloc>
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240 insert_only_hash_map <T, Alloc>*
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241 insert_only_hash_map <T, Alloc>::put_internal (
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242 const insert_only_hash_map::key_type *k,
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243 const insert_only_hash_map::value_type &v,
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244 bool unique_key_and_resize_not_needed)
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245 {
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246 /* Table size is always a power of 2. */
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247 const size_type mask = this->bucket_count () - 1;
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248 size_type bucket_index = k->hash & mask;
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249 size_type step = 1;
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250 for (;;)
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251 {
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252 bucket_type &bucket = this->buckets[bucket_index];
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253 if (bucket.first == NULL)
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254 {
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255 /* Key was not present. */
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256 if (!unique_key_and_resize_not_needed
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257 && this->is_too_full (this->size () + 1))
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258 {
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259 insert_only_hash_map <T, Alloc>* result =
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260 this->destructive_copy ();
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261 return result == NULL
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262 ? NULL
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263 : result->put_internal (k, v, true);
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264 }
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265 else
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266 {
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267 bucket.first = k;
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268 bucket.second = v;
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269 this->num_entries_++;
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270 return this;
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271 }
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272 }
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273 else if (!unique_key_and_resize_not_needed && bucket.first->equals (k))
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274 {
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275 /* Key was present. Just change the value. */
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276 bucket.second = v;
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277 return this;
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278 }
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279 else
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280 bucket_index = (bucket_index + step++) & mask;
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281 }
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282 }
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283
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284 template <typename T, typename Alloc>
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285 inline const typename insert_only_hash_map <T, Alloc>::value_type*
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286 insert_only_hash_map <T, Alloc>::get (const insert_only_hash_map::key_type *k)
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287 const
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288 {
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289 /* Table size is always a power of 2. */
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290 const size_type mask = this->bucket_count () - 1;
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291 size_type bucket_index = k->hash & mask;
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292 size_type step = 1;
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293 for (;;)
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294 {
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295 const bucket_type &bucket = this->buckets[bucket_index];
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296 if (bucket.first == NULL)
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297 return NULL;
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298 else if (bucket.first->equals (k))
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299 return &bucket.second;
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300 else
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301 bucket_index = (bucket_index + step++) & mask;
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302 }
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303 }
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304
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305 template <typename T, typename Alloc>
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306 inline bool
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307 insert_only_hash_map <T, Alloc>::key_type::equals (
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308 const typename insert_only_hash_map <T, Alloc>::key_type *k) const
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309 {
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310 const char* x = reinterpret_cast <const char *> (k);
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311 const char* y = reinterpret_cast <const char *> (this);
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312 return (load8bytes (x) == load8bytes (y)
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313 && memcmp (x + 8, y + 8, this->n) == 0);
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314 }
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315
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316 #endif /* _VTV_MAP_H */
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