1 | // Copyright (c) 2005, Google Inc.
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2 | // All rights reserved.
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3 | //
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4 | // Redistribution and use in source and binary forms, with or without
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5 | // modification, are permitted provided that the following conditions are
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6 | // met:
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7 | //
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8 | // * Redistributions of source code must retain the above copyright
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9 | // notice, this list of conditions and the following disclaimer.
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10 | // * Redistributions in binary form must reproduce the above
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11 | // copyright notice, this list of conditions and the following disclaimer
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12 | // in the documentation and/or other materials provided with the
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13 | // distribution.
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14 | // * Neither the name of Google Inc. nor the names of its
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15 | // contributors may be used to endorse or promote products derived from
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16 | // this software without specific prior written permission.
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17 | //
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18 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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19 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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20 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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21 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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22 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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23 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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24 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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25 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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26 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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27 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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28 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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29 |
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30 | // ---
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31 | // Author: Craig Silverstein
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32 | //
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33 | // A sparse hashtable is a particular implementation of
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34 | // a hashtable: one that is meant to minimize memory use.
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35 | // It does this by using a *sparse table* (cf sparsetable.h),
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36 | // which uses between 1 and 2 bits to store empty buckets
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37 | // (we may need another bit for hashtables that support deletion).
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38 | //
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39 | // When empty buckets are so cheap, an appealing hashtable
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40 | // implementation is internal probing, in which the hashtable
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41 | // is a single table, and collisions are resolved by trying
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42 | // to insert again in another bucket. The most cache-efficient
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43 | // internal probing schemes are linear probing (which suffers,
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44 | // alas, from clumping) and quadratic probing, which is what
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45 | // we implement by default.
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46 | //
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47 | // Deleted buckets are a bit of a pain. We have to somehow mark
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48 | // deleted buckets (the probing must distinguish them from empty
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49 | // buckets). The most principled way is to have another bitmap,
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50 | // but that's annoying and takes up space. Instead we let the
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51 | // user specify an "impossible" key. We set deleted buckets
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52 | // to have the impossible key.
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53 | //
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54 | // Note it is possible to change the value of the delete key
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55 | // on the fly; you can even remove it, though after that point
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56 | // the hashtable is insert_only until you set it again.
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57 | //
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58 | // You probably shouldn't use this code directly. Use
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59 | // <google/sparse_hash_table> or <google/sparse_hash_set> instead.
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60 |
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61 | // You can change the following below:
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62 | // HT_OCCUPANCY_FLT -- how full before we double size
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63 | // HT_EMPTY_FLT -- how empty before we halve size
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64 | // HT_MIN_BUCKETS -- smallest bucket size
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65 | //
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66 | // How to decide what values to use?
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67 | // HT_EMPTY_FLT's default of .4 * OCCUPANCY_FLT, is probably good.
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68 | // HT_MIN_BUCKETS is probably unnecessary since you can specify
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69 | // (indirectly) the starting number of buckets at construct-time.
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70 | // For HT_OCCUPANCY_FLT, you can use this chart to try to trade-off
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71 | // expected lookup time to the space taken up. By default, this
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72 | // code uses quadratic probing, though you can change it to linear
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73 | // via _JUMP below if you really want to.
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74 | //
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75 | // From http://www.augustana.ca/~mohrj/courses/1999.fall/csc210/lecture_notes/hashing.html
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76 | // NUMBER OF PROBES / LOOKUP Successful Unsuccessful
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77 | // Quadratic collision resolution 1 - ln(1-L) - L/2 1/(1-L) - L - ln(1-L)
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78 | // Linear collision resolution [1+1/(1-L)]/2 [1+1/(1-L)2]/2
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79 | //
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80 | // -- HT_OCCUPANCY_FLT -- 0.10 0.50 0.60 0.75 0.80 0.90 0.99
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81 | // QUADRATIC COLLISION RES.
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82 | // probes/successful lookup 1.05 1.44 1.62 2.01 2.21 2.85 5.11
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83 | // probes/unsuccessful lookup 1.11 2.19 2.82 4.64 5.81 11.4 103.6
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84 | // LINEAR COLLISION RES.
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85 | // probes/successful lookup 1.06 1.5 1.75 2.5 3.0 5.5 50.5
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86 | // probes/unsuccessful lookup 1.12 2.5 3.6 8.5 13.0 50.0 5000.0
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87 |
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88 |
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89 | #ifndef _SPARSEHASHTABLE_H_
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90 | #define _SPARSEHASHTABLE_H_
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91 |
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92 | #ifndef SPARSEHASH_STAT_UPDATE
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93 | #define SPARSEHASH_STAT_UPDATE(x) ((void) 0)
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94 | #endif
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95 |
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96 | // The probing method
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97 | // Linear probing
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98 | // #define JUMP_(key, num_probes) ( 1 )
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99 | // Quadratic-ish probing
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100 | #define JUMP_(key, num_probes) ( num_probes )
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101 |
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102 |
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103 | // Hashtable class, used to implement the hashed associative containers
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104 | // hash_set and hash_map.
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105 |
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106 | #include <google/sparsehash/config.h>
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107 | #include <assert.h>
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108 | #include <algorithm> // For swap(), eg
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109 | #include <google/sparsetable> // Since that's basically what we are
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110 |
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111 | _START_GOOGLE_NAMESPACE_
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112 |
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113 | using STL_NAMESPACE::pair;
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114 |
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115 | // sparsetable uses malloc()/realloc()/free(), so Alloc is basically
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116 | // ignored. We include it because we're being compatible.
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117 | // TODO(csilvers): is that the right thing to do?
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118 |
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119 | template <class Value, class Key, class HashFcn,
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120 | class ExtractKey, class EqualKey, class Alloc>
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121 | class sparse_hashtable;
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122 |
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123 | template <class V, class K, class HF, class ExK, class EqK, class A>
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124 | struct sparse_hashtable_iterator;
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125 |
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126 | template <class V, class K, class HF, class ExK, class EqK, class A>
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127 | struct sparse_hashtable_const_iterator;
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128 |
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129 | // As far as iterating, we're basically just a sparsetable
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130 | // that skips over deleted elements.
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131 | template <class V, class K, class HF, class ExK, class EqK, class A>
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132 | struct sparse_hashtable_iterator {
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133 | public:
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134 | typedef sparse_hashtable<V,K,HF,ExK,EqK,A> sparse_hashtable;
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135 | typedef sparse_hashtable_iterator<V,K,HF,ExK,EqK,A> iterator;
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136 | typedef sparse_hashtable_const_iterator<V,K,HF,ExK,EqK,A> const_iterator;
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137 | typedef typename sparsetable<V>::nonempty_iterator st_iterator;
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138 |
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139 | #ifdef UNDERSTANDS_ITERATOR_TAGS
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140 | typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
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141 | #endif
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142 | typedef V value_type;
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143 | typedef ptrdiff_t difference_type;
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144 | typedef size_t size_type;
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145 | typedef V& reference; // Value
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146 | typedef V* pointer;
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147 |
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148 | // "Real" constructor and default constructor
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149 | sparse_hashtable_iterator(const sparse_hashtable *h,
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150 | st_iterator it, st_iterator it_end)
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151 | : ht(h), pos(it), end(it_end) { advance_past_deleted(); }
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152 | sparse_hashtable_iterator() { } // not ever used internally
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153 | // The default destructor is fine; we don't define one
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154 | // The default operator= is fine; we don't define one
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155 |
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156 | // Happy dereferencer
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157 | reference operator*() const { return *pos; }
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158 | pointer operator->() const { return &(operator*()); }
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159 |
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160 | // Arithmetic. The only hard part is making sure that
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161 | // we're not on a marked-deleted array element
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162 | void advance_past_deleted() {
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163 | while ( pos != end && ht->test_deleted(*this) )
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164 | ++pos;
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165 | }
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166 | iterator& operator++() {
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167 | assert(pos != end); ++pos; advance_past_deleted(); return *this;
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168 | }
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169 | iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }
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170 |
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171 | // Comparison.
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172 | bool operator==(const iterator& it) const { return pos == it.pos; }
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173 | bool operator!=(const iterator& it) const { return pos != it.pos; }
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174 |
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175 |
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176 | // The actual data
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177 | const sparse_hashtable *ht;
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178 | st_iterator pos, end;
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179 | };
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180 |
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181 | // Now do it all again, but with const-ness!
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182 | template <class V, class K, class HF, class ExK, class EqK, class A>
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183 | struct sparse_hashtable_const_iterator {
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184 | public:
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185 | typedef sparse_hashtable<V,K,HF,ExK,EqK,A> sparse_hashtable;
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186 | typedef sparse_hashtable_iterator<V,K,HF,ExK,EqK,A> iterator;
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187 | typedef sparse_hashtable_const_iterator<V,K,HF,ExK,EqK,A> const_iterator;
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188 | typedef typename sparsetable<V>::const_nonempty_iterator st_iterator;
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189 |
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190 | #ifdef UNDERSTANDS_ITERATOR_TAGS
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191 | typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
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192 | #endif
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193 | typedef V value_type;
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194 | typedef ptrdiff_t difference_type;
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195 | typedef size_t size_type;
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196 | typedef const V& reference; // Value
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197 | typedef const V* pointer;
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198 |
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199 | // "Real" constructor and default constructor
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200 | sparse_hashtable_const_iterator(const sparse_hashtable *h,
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201 | st_iterator it, st_iterator it_end)
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202 | : ht(h), pos(it), end(it_end) { advance_past_deleted(); }
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203 | // This lets us convert regular iterators to const iterators
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204 | sparse_hashtable_const_iterator() { } // never used internally
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205 | sparse_hashtable_const_iterator(const iterator &it)
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206 | : ht(it.ht), pos(it.pos), end(it.end) { }
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207 | // The default destructor is fine; we don't define one
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208 | // The default operator= is fine; we don't define one
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209 |
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210 | // Happy dereferencer
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211 | reference operator*() const { return *pos; }
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212 | pointer operator->() const { return &(operator*()); }
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213 |
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214 | // Arithmetic. The only hard part is making sure that
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215 | // we're not on a marked-deleted array element
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216 | void advance_past_deleted() {
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217 | while ( pos != end && ht->test_deleted(*this) )
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218 | ++pos;
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219 | }
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220 | const_iterator& operator++() {
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221 | assert(pos != end); ++pos; advance_past_deleted(); return *this;
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222 | }
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223 | const_iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }
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224 |
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225 | // Comparison.
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226 | bool operator==(const const_iterator& it) const { return pos == it.pos; }
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227 | bool operator!=(const const_iterator& it) const { return pos != it.pos; }
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228 |
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229 |
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230 | // The actual data
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231 | const sparse_hashtable *ht;
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232 | st_iterator pos, end;
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233 | };
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234 |
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235 | // And once again, but this time freeing up memory as we iterate
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236 | template <class V, class K, class HF, class ExK, class EqK, class A>
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237 | struct sparse_hashtable_destructive_iterator {
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238 | public:
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239 | typedef sparse_hashtable<V,K,HF,ExK,EqK,A> sparse_hashtable;
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240 | typedef sparse_hashtable_destructive_iterator<V,K,HF,ExK,EqK,A> iterator;
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241 | typedef typename sparsetable<V>::destructive_iterator st_iterator;
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242 |
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243 | #ifdef UNDERSTANDS_ITERATOR_TAGS
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244 | typedef STL_NAMESPACE::forward_iterator_tag iterator_category;
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245 | #endif
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246 | typedef V value_type;
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247 | typedef ptrdiff_t difference_type;
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248 | typedef size_t size_type;
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249 | typedef V& reference; // Value
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250 | typedef V* pointer;
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251 |
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252 | // "Real" constructor and default constructor
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253 | sparse_hashtable_destructive_iterator(const sparse_hashtable *h,
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254 | st_iterator it, st_iterator it_end)
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255 | : ht(h), pos(it), end(it_end) { advance_past_deleted(); }
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256 | sparse_hashtable_destructive_iterator() { } // never used internally
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257 | // The default destructor is fine; we don't define one
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258 | // The default operator= is fine; we don't define one
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259 |
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260 | // Happy dereferencer
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261 | reference operator*() const { return *pos; }
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262 | pointer operator->() const { return &(operator*()); }
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263 |
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264 | // Arithmetic. The only hard part is making sure that
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265 | // we're not on a marked-deleted array element
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266 | void advance_past_deleted() {
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267 | while ( pos != end && ht->test_deleted(*this) )
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268 | ++pos;
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269 | }
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270 | iterator& operator++() {
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271 | assert(pos != end); ++pos; advance_past_deleted(); return *this;
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272 | }
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273 | iterator operator++(int) { iterator tmp(*this); ++*this; return tmp; }
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274 |
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275 | // Comparison.
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276 | bool operator==(const iterator& it) const { return pos == it.pos; }
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277 | bool operator!=(const iterator& it) const { return pos != it.pos; }
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278 |
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279 |
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280 | // The actual data
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281 | const sparse_hashtable *ht;
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282 | st_iterator pos, end;
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283 | };
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284 |
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285 |
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286 |
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287 | template <class Value, class Key, class HashFcn,
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288 | class ExtractKey, class EqualKey, class Alloc>
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289 | class sparse_hashtable {
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290 | public:
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291 | typedef Key key_type;
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292 | typedef Value value_type;
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293 | typedef HashFcn hasher;
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294 | typedef EqualKey key_equal;
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295 |
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296 | typedef size_t size_type;
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297 | typedef ptrdiff_t difference_type;
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298 | typedef value_type* pointer;
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299 | typedef const value_type* const_pointer;
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300 | typedef value_type& reference;
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301 | typedef const value_type& const_reference;
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302 | typedef sparse_hashtable_iterator<Value, Key, HashFcn,
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303 | ExtractKey, EqualKey, Alloc>
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304 | iterator;
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305 |
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306 | typedef sparse_hashtable_const_iterator<Value, Key, HashFcn,
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307 | ExtractKey, EqualKey, Alloc>
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308 | const_iterator;
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309 |
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310 | typedef sparse_hashtable_destructive_iterator<Value, Key, HashFcn,
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311 | ExtractKey, EqualKey, Alloc>
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312 | destructive_iterator;
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313 |
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314 | // How full we let the table get before we resize. Knuth says .8 is
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315 | // good -- higher causes us to probe too much, though saves memory
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316 | static const float HT_OCCUPANCY_FLT; // = 0.8f;
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317 |
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318 | // How empty we let the table get before we resize lower.
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319 | // It should be less than OCCUPANCY_FLT / 2 or we thrash resizing
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320 | static const float HT_EMPTY_FLT; // = 0.4 * HT_OCCUPANCY_FLT;
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321 |
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322 | // Minimum size we're willing to let hashtables be.
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323 | // Must be a power of two, and at least 4.
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324 | // Note, however, that for a given hashtable, the minimum size is
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325 | // determined by the first constructor arg, and may be >HT_MIN_BUCKETS.
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326 | static const size_t HT_MIN_BUCKETS = 32;
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327 |
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328 |
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329 | // ITERATOR FUNCTIONS
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330 | iterator begin() { return iterator(this, table.nonempty_begin(),
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331 | table.nonempty_end()); }
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332 | iterator end() { return iterator(this, table.nonempty_end(),
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333 | table.nonempty_end()); }
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334 | const_iterator begin() const { return const_iterator(this,
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335 | table.nonempty_begin(),
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336 | table.nonempty_end()); }
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337 | const_iterator end() const { return const_iterator(this,
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338 | table.nonempty_end(),
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339 | table.nonempty_end()); }
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340 |
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341 | // This is used when resizing
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342 | destructive_iterator destructive_begin() {
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343 | return destructive_iterator(this, table.destructive_begin(),
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344 | table.destructive_end());
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345 | }
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346 | destructive_iterator destructive_end() {
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347 | return destructive_iterator(this, table.destructive_end(),
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348 | table.destructive_end());
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349 | }
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350 |
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351 |
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352 | // ACCESSOR FUNCTIONS for the things we templatize on, basically
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353 | hasher hash_funct() const { return hash; }
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354 | key_equal key_eq() const { return equals; }
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355 |
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356 | // Annoyingly, we can't copy values around, because they might have
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357 | // const components (they're probably pair<const X, Y>). We use
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358 | // placement new to get around this. Arg.
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359 | private:
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360 | void set_value(value_type* dst, const value_type src) {
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361 | new(dst) value_type(src);
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362 | }
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363 |
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364 | void set_key(key_type* dst, const key_type src) {
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365 | new(dst) key_type(src); // used for set_deleted_key(), etc
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366 | }
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367 |
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368 | // This is used as a tag for the copy constructor, saying to destroy its
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369 | // arg We have two ways of destructively copying: with potentially growing
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370 | // the hashtable as we copy, and without. To make sure the outside world
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371 | // can't do a destructive copy, we make the typename private.
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372 | enum MoveDontCopyT {MoveDontCopy, MoveDontGrow};
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373 |
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374 |
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375 | // DELETE HELPER FUNCTIONS
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376 | // This lets the user describe a key that will indicate deleted
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377 | // table entries. This key should be an "impossible" entry --
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378 | // if you try to insert it for real, you won't be able to retrieve it!
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379 | // (NB: while you pass in an entire value, only the key part is looked
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380 | // at. This is just because I don't know how to assign just a key.)
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381 | private:
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382 | void squash_deleted() { // gets rid of any deleted entries we have
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383 | if ( num_deleted ) { // get rid of deleted before writing
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384 | sparse_hashtable tmp(MoveDontGrow, *this);
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385 | swap(tmp); // now we are tmp
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386 | }
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387 | assert(num_deleted == 0);
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388 | }
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389 |
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390 | public:
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391 | void set_deleted_key(const key_type &key) {
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392 | // It's only safe to change what "deleted" means if we purge deleted guys
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393 | squash_deleted();
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394 | use_deleted = true;
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395 | set_key(&delkey, key); // save the key
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396 | }
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397 | void clear_deleted_key() {
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398 | squash_deleted();
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399 | use_deleted = false;
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400 | }
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401 |
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402 | // These are public so the iterators can use them
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403 | // True if the item at position bucknum is "deleted" marker
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404 | bool test_deleted(size_type bucknum) const {
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405 | // The num_deleted test is crucial for read(): after read(), the ht values
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406 | // are garbage, and we don't want to think some of them are deleted.
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407 | return (use_deleted && num_deleted > 0 && table.test(bucknum) &&
|
---|
408 | equals(delkey, get_key(table.get(bucknum))));
|
---|
409 | }
|
---|
410 | bool test_deleted(const iterator &it) const {
|
---|
411 | return (use_deleted && num_deleted > 0 &&
|
---|
412 | equals(delkey, get_key(*it)));
|
---|
413 | }
|
---|
414 | bool test_deleted(const const_iterator &it) const {
|
---|
415 | return (use_deleted && num_deleted > 0 &&
|
---|
416 | equals(delkey, get_key(*it)));
|
---|
417 | }
|
---|
418 | bool test_deleted(const destructive_iterator &it) const {
|
---|
419 | return (use_deleted && num_deleted > 0 &&
|
---|
420 | equals(delkey, get_key(*it)));
|
---|
421 | }
|
---|
422 | // Set it so test_deleted is true. true if object didn't used to be deleted
|
---|
423 | // See below (at erase()) to explain why we allow const_iterators
|
---|
424 | bool set_deleted(const_iterator &it) {
|
---|
425 | assert(use_deleted); // bad if set_deleted_key() wasn't called
|
---|
426 | bool retval = !test_deleted(it);
|
---|
427 | // &* converts from iterator to value-type
|
---|
428 | set_key(const_cast<key_type*>(&get_key(*it)), delkey);
|
---|
429 | return retval;
|
---|
430 | }
|
---|
431 | // Set it so test_deleted is false. true if object used to be deleted
|
---|
432 | bool clear_deleted(const_iterator &it) {
|
---|
433 | assert(use_deleted); // bad if set_deleted_key() wasn't called
|
---|
434 | // happens automatically when we assign something else in its place
|
---|
435 | return test_deleted(it);
|
---|
436 | }
|
---|
437 |
|
---|
438 |
|
---|
439 | // FUNCTIONS CONCERNING SIZE
|
---|
440 | size_type size() const { return table.num_nonempty() - num_deleted; }
|
---|
441 | // Buckets are always a power of 2
|
---|
442 | size_type max_size() const { return (size_type(-1) >> 1U) + 1; }
|
---|
443 | bool empty() const { return size() == 0; }
|
---|
444 | size_type bucket_count() const { return table.size(); }
|
---|
445 | size_type max_bucket_count() const { return max_size(); }
|
---|
446 |
|
---|
447 | private:
|
---|
448 | // Because of the above, size_type(-1) is never legal; use it for errors
|
---|
449 | static const size_type ILLEGAL_BUCKET = size_type(-1);
|
---|
450 |
|
---|
451 | private:
|
---|
452 | // This is the smallest size a hashtable can be without being too crowded
|
---|
453 | // If you like, you can give a min #buckets as well as a min #elts
|
---|
454 | size_type min_size(size_type num_elts, size_type min_buckets_wanted) {
|
---|
455 | size_type sz = HT_MIN_BUCKETS;
|
---|
456 | while ( sz < min_buckets_wanted || num_elts >= sz * HT_OCCUPANCY_FLT )
|
---|
457 | sz *= 2;
|
---|
458 | return sz;
|
---|
459 | }
|
---|
460 |
|
---|
461 | // Used after a string of deletes
|
---|
462 | void maybe_shrink() {
|
---|
463 | assert(table.num_nonempty() >= num_deleted);
|
---|
464 | assert((bucket_count() & (bucket_count()-1)) == 0); // is a power of two
|
---|
465 | assert(bucket_count() >= HT_MIN_BUCKETS);
|
---|
466 |
|
---|
467 | if ( (table.num_nonempty()-num_deleted) <= shrink_threshold &&
|
---|
468 | bucket_count() > HT_MIN_BUCKETS ) {
|
---|
469 | size_type sz = bucket_count() / 2; // find how much we should shrink
|
---|
470 | while ( sz > HT_MIN_BUCKETS &&
|
---|
471 | (table.num_nonempty() - num_deleted) <= sz * HT_EMPTY_FLT )
|
---|
472 | sz /= 2; // stay a power of 2
|
---|
473 | sparse_hashtable tmp(MoveDontCopy, *this, sz);
|
---|
474 | swap(tmp); // now we are tmp
|
---|
475 | }
|
---|
476 | consider_shrink = false; // because we just considered it
|
---|
477 | }
|
---|
478 |
|
---|
479 | // We'll let you resize a hashtable -- though this makes us copy all!
|
---|
480 | // When you resize, you say, "make it big enough for this many more elements"
|
---|
481 | void resize_delta(size_type delta, size_type min_buckets_wanted = 0) {
|
---|
482 | if ( consider_shrink ) // see if lots of deletes happened
|
---|
483 | maybe_shrink();
|
---|
484 | if ( bucket_count() > min_buckets_wanted &&
|
---|
485 | (table.num_nonempty() + delta) <= enlarge_threshold )
|
---|
486 | return; // we're ok as we are
|
---|
487 |
|
---|
488 | const size_type resize_to = min_size(table.num_nonempty() + delta,
|
---|
489 | min_buckets_wanted);
|
---|
490 | if ( resize_to > bucket_count() ) { // we don't have enough buckets
|
---|
491 | sparse_hashtable tmp(MoveDontCopy, *this, resize_to);
|
---|
492 | swap(tmp); // now we are tmp
|
---|
493 | }
|
---|
494 | }
|
---|
495 |
|
---|
496 | // Used to actually do the rehashing when we grow/shrink a hashtable
|
---|
497 | void copy_from(const sparse_hashtable &ht, size_type min_buckets_wanted = 0) {
|
---|
498 | clear(); // clear table, set num_deleted to 0
|
---|
499 |
|
---|
500 | // If we need to change the size of our table, do it now
|
---|
501 | const size_type resize_to = min_size(ht.size(), min_buckets_wanted);
|
---|
502 | if ( resize_to > bucket_count() ) { // we don't have enough buckets
|
---|
503 | table.resize(resize_to); // sets the number of buckets
|
---|
504 | reset_thresholds();
|
---|
505 | }
|
---|
506 |
|
---|
507 | // We use a normal iterator to get non-deleted bcks from ht
|
---|
508 | // We could use insert() here, but since we know there are
|
---|
509 | // no duplicates and no deleted items, we can be more efficient
|
---|
510 | assert( (bucket_count() & (bucket_count()-1)) == 0); // a power of two
|
---|
511 | for ( const_iterator it = ht.begin(); it != ht.end(); ++it ) {
|
---|
512 | size_type num_probes = 0; // how many times we've probed
|
---|
513 | size_type bucknum;
|
---|
514 | const size_type bucket_count_minus_one = bucket_count() - 1;
|
---|
515 | for (bucknum = hash(get_key(*it)) & bucket_count_minus_one;
|
---|
516 | table.test(bucknum); // not empty
|
---|
517 | bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one) {
|
---|
518 | ++num_probes;
|
---|
519 | assert(num_probes < bucket_count()); // or else the hashtable is full
|
---|
520 | }
|
---|
521 | table.set(bucknum, *it); // copies the value to here
|
---|
522 | }
|
---|
523 | }
|
---|
524 |
|
---|
525 | // Implementation is like copy_from, but it destroys the table of the
|
---|
526 | // "from" guy by freeing sparsetable memory as we iterate. This is
|
---|
527 | // useful in resizing, since we're throwing away the "from" guy anyway.
|
---|
528 | void move_from(MoveDontCopyT mover, sparse_hashtable &ht,
|
---|
529 | size_type min_buckets_wanted = 0) {
|
---|
530 | clear(); // clear table, set num_deleted to 0
|
---|
531 |
|
---|
532 | // If we need to change the size of our table, do it now
|
---|
533 | size_t resize_to;
|
---|
534 | if ( mover == MoveDontGrow )
|
---|
535 | resize_to = ht.bucket_count(); // keep same size as old ht
|
---|
536 | else // MoveDontCopy
|
---|
537 | resize_to = min_size(ht.size(), min_buckets_wanted);
|
---|
538 | if ( resize_to > bucket_count() ) { // we don't have enough buckets
|
---|
539 | table.resize(resize_to); // sets the number of buckets
|
---|
540 | reset_thresholds();
|
---|
541 | }
|
---|
542 |
|
---|
543 | // We use a normal iterator to get non-deleted bcks from ht
|
---|
544 | // We could use insert() here, but since we know there are
|
---|
545 | // no duplicates and no deleted items, we can be more efficient
|
---|
546 | assert( (bucket_count() & (bucket_count()-1)) == 0); // a power of two
|
---|
547 | // THIS IS THE MAJOR LINE THAT DIFFERS FROM COPY_FROM():
|
---|
548 | for ( destructive_iterator it = ht.destructive_begin();
|
---|
549 | it != ht.destructive_end(); ++it ) {
|
---|
550 | size_type num_probes = 0; // how many times we've probed
|
---|
551 | size_type bucknum;
|
---|
552 | for ( bucknum = hash(get_key(*it)) & (bucket_count()-1); // h % buck_cnt
|
---|
553 | table.test(bucknum); // not empty
|
---|
554 | bucknum = (bucknum + JUMP_(key, num_probes)) & (bucket_count()-1) ) {
|
---|
555 | ++num_probes;
|
---|
556 | assert(num_probes < bucket_count()); // or else the hashtable is full
|
---|
557 | }
|
---|
558 | table.set(bucknum, *it); // copies the value to here
|
---|
559 | }
|
---|
560 | }
|
---|
561 |
|
---|
562 |
|
---|
563 | // Required by the spec for hashed associative container
|
---|
564 | public:
|
---|
565 | // Though the docs say this should be num_buckets, I think it's much
|
---|
566 | // more useful as num_elements. As a special feature, calling with
|
---|
567 | // req_elements==0 will cause us to shrink if we can, saving space.
|
---|
568 | void resize(size_type req_elements) { // resize to this or larger
|
---|
569 | if ( consider_shrink || req_elements == 0 )
|
---|
570 | maybe_shrink();
|
---|
571 | if ( req_elements > table.num_nonempty() ) // we only grow
|
---|
572 | resize_delta(req_elements - table.num_nonempty(), 0);
|
---|
573 | }
|
---|
574 |
|
---|
575 |
|
---|
576 | // CONSTRUCTORS -- as required by the specs, we take a size,
|
---|
577 | // but also let you specify a hashfunction, key comparator,
|
---|
578 | // and key extractor. We also define a copy constructor and =.
|
---|
579 | // DESTRUCTOR -- the default is fine, surprisingly.
|
---|
580 | explicit sparse_hashtable(size_type n = 0,
|
---|
581 | const HashFcn& hf = HashFcn(),
|
---|
582 | const EqualKey& eql = EqualKey(),
|
---|
583 | const ExtractKey& ext = ExtractKey())
|
---|
584 | : hash(hf), equals(eql), get_key(ext), num_deleted(0),
|
---|
585 | use_deleted(false), delkey(), table(min_size(0, n)) { // start small
|
---|
586 | reset_thresholds();
|
---|
587 | }
|
---|
588 |
|
---|
589 | // As a convenience for resize(), we allow an optional second argument
|
---|
590 | // which lets you make this new hashtable a different size than ht.
|
---|
591 | // We also provide a mechanism of saying you want to "move" the ht argument
|
---|
592 | // into us instead of copying.
|
---|
593 | sparse_hashtable(const sparse_hashtable& ht, size_type min_buckets_wanted = 0)
|
---|
594 | : hash(ht.hash), equals(ht.equals), get_key(ht.get_key),
|
---|
595 | num_deleted(0), use_deleted(ht.use_deleted), delkey(ht.delkey), table() {
|
---|
596 | reset_thresholds();
|
---|
597 | copy_from(ht, min_buckets_wanted); // copy_from() ignores deleted entries
|
---|
598 | }
|
---|
599 | sparse_hashtable(MoveDontCopyT mover, sparse_hashtable& ht,
|
---|
600 | size_type min_buckets_wanted=0)
|
---|
601 | : hash(ht.hash), equals(ht.equals), get_key(ht.get_key),
|
---|
602 | num_deleted(0), use_deleted(ht.use_deleted), delkey(ht.delkey), table() {
|
---|
603 | reset_thresholds();
|
---|
604 | move_from(mover, ht, min_buckets_wanted); // ignores deleted entries
|
---|
605 | }
|
---|
606 |
|
---|
607 | sparse_hashtable& operator= (const sparse_hashtable& ht) {
|
---|
608 | if (&ht == this) return *this; // don't copy onto ourselves
|
---|
609 | clear();
|
---|
610 | hash = ht.hash;
|
---|
611 | equals = ht.equals;
|
---|
612 | get_key = ht.get_key;
|
---|
613 | use_deleted = ht.use_deleted;
|
---|
614 | set_key(&delkey, ht.delkey);
|
---|
615 | copy_from(ht); // sets num_deleted to 0 too
|
---|
616 | return *this;
|
---|
617 | }
|
---|
618 |
|
---|
619 | // Many STL algorithms use swap instead of copy constructors
|
---|
620 | void swap(sparse_hashtable& ht) {
|
---|
621 | STL_NAMESPACE::swap(hash, ht.hash);
|
---|
622 | STL_NAMESPACE::swap(equals, ht.equals);
|
---|
623 | STL_NAMESPACE::swap(get_key, ht.get_key);
|
---|
624 | STL_NAMESPACE::swap(num_deleted, ht.num_deleted);
|
---|
625 | STL_NAMESPACE::swap(use_deleted, ht.use_deleted);
|
---|
626 | { key_type tmp; // for annoying reasons, swap() doesn't work
|
---|
627 | set_key(&tmp, delkey);
|
---|
628 | set_key(&delkey, ht.delkey);
|
---|
629 | set_key(&ht.delkey, tmp);
|
---|
630 | }
|
---|
631 | table.swap(ht.table);
|
---|
632 | reset_thresholds();
|
---|
633 | ht.reset_thresholds();
|
---|
634 | }
|
---|
635 |
|
---|
636 | // It's always nice to be able to clear a table without deallocating it
|
---|
637 | void clear() {
|
---|
638 | table.clear();
|
---|
639 | reset_thresholds();
|
---|
640 | num_deleted = 0;
|
---|
641 | }
|
---|
642 |
|
---|
643 |
|
---|
644 | // LOOKUP ROUTINES
|
---|
645 | private:
|
---|
646 | // Returns a pair of positions: 1st where the object is, 2nd where
|
---|
647 | // it would go if you wanted to insert it. 1st is ILLEGAL_BUCKET
|
---|
648 | // if object is not found; 2nd is ILLEGAL_BUCKET if it is.
|
---|
649 | // Note: because of deletions where-to-insert is not trivial: it's the
|
---|
650 | // first deleted bucket we see, as long as we don't find the key later
|
---|
651 | pair<size_type, size_type> find_position(const key_type &key) const {
|
---|
652 | size_type num_probes = 0; // how many times we've probed
|
---|
653 | const size_type bucket_count_minus_one = bucket_count() - 1;
|
---|
654 | size_type bucknum = hash(key) & bucket_count_minus_one;
|
---|
655 | size_type insert_pos = ILLEGAL_BUCKET; // where we would insert
|
---|
656 | SPARSEHASH_STAT_UPDATE(total_lookups += 1);
|
---|
657 | while ( 1 ) { // probe until something happens
|
---|
658 | if ( !table.test(bucknum) ) { // bucket is empty
|
---|
659 | SPARSEHASH_STAT_UPDATE(total_probes += num_probes);
|
---|
660 | if ( insert_pos == ILLEGAL_BUCKET ) // found no prior place to insert
|
---|
661 | return pair<size_type,size_type>(ILLEGAL_BUCKET, bucknum);
|
---|
662 | else
|
---|
663 | return pair<size_type,size_type>(ILLEGAL_BUCKET, insert_pos);
|
---|
664 |
|
---|
665 | } else if ( test_deleted(bucknum) ) {// keep searching, but mark to insert
|
---|
666 | if ( insert_pos == ILLEGAL_BUCKET )
|
---|
667 | insert_pos = bucknum;
|
---|
668 |
|
---|
669 | } else if ( equals(key, get_key(table.get(bucknum))) ) {
|
---|
670 | SPARSEHASH_STAT_UPDATE(total_probes += num_probes);
|
---|
671 | return pair<size_type,size_type>(bucknum, ILLEGAL_BUCKET);
|
---|
672 | }
|
---|
673 | ++num_probes; // we're doing another probe
|
---|
674 | bucknum = (bucknum + JUMP_(key, num_probes)) & bucket_count_minus_one;
|
---|
675 | assert(num_probes < bucket_count()); // don't probe too many times!
|
---|
676 | }
|
---|
677 | }
|
---|
678 |
|
---|
679 | public:
|
---|
680 | iterator find(const key_type& key) {
|
---|
681 | if ( size() == 0 ) return end();
|
---|
682 | pair<size_type, size_type> pos = find_position(key);
|
---|
683 | if ( pos.first == ILLEGAL_BUCKET ) // alas, not there
|
---|
684 | return end();
|
---|
685 | else
|
---|
686 | return iterator(this, table.get_iter(pos.first), table.nonempty_end());
|
---|
687 | }
|
---|
688 |
|
---|
689 | const_iterator find(const key_type& key) const {
|
---|
690 | if ( size() == 0 ) return end();
|
---|
691 | pair<size_type, size_type> pos = find_position(key);
|
---|
692 | if ( pos.first == ILLEGAL_BUCKET ) // alas, not there
|
---|
693 | return end();
|
---|
694 | else
|
---|
695 | return const_iterator(this,
|
---|
696 | table.get_iter(pos.first), table.nonempty_end());
|
---|
697 | }
|
---|
698 |
|
---|
699 | // Counts how many elements have key key. For maps, it's either 0 or 1.
|
---|
700 | size_type count(const key_type &key) const {
|
---|
701 | pair<size_type, size_type> pos = find_position(key);
|
---|
702 | return pos.first == ILLEGAL_BUCKET ? 0 : 1;
|
---|
703 | }
|
---|
704 |
|
---|
705 | // Likewise, equal_range doesn't really make sense for us. Oh well.
|
---|
706 | pair<iterator,iterator> equal_range(const key_type& key) {
|
---|
707 | const iterator pos = find(key); // either an iterator or end
|
---|
708 | return pair<iterator,iterator>(pos, pos);
|
---|
709 | }
|
---|
710 | pair<const_iterator,const_iterator> equal_range(const key_type& key) const {
|
---|
711 | const const_iterator pos = find(key); // either an iterator or end
|
---|
712 | return pair<iterator,iterator>(pos, pos);
|
---|
713 | }
|
---|
714 |
|
---|
715 |
|
---|
716 | // INSERTION ROUTINES
|
---|
717 | private:
|
---|
718 | // If you know *this is big enough to hold obj, use this routine
|
---|
719 | pair<iterator, bool> insert_noresize(const value_type& obj) {
|
---|
720 | const pair<size_type,size_type> pos = find_position(get_key(obj));
|
---|
721 | if ( pos.first != ILLEGAL_BUCKET) { // object was already there
|
---|
722 | return pair<iterator,bool>(iterator(this, table.get_iter(pos.first),
|
---|
723 | table.nonempty_end()),
|
---|
724 | false); // false: we didn't insert
|
---|
725 | } else { // pos.second says where to put it
|
---|
726 | if ( test_deleted(pos.second) ) { // just replace if it's been del.
|
---|
727 | // The set() below will undelete this object. We just worry about stats
|
---|
728 | assert(num_deleted > 0);
|
---|
729 | --num_deleted; // used to be, now it isn't
|
---|
730 | }
|
---|
731 | table.set(pos.second, obj);
|
---|
732 | return pair<iterator,bool>(iterator(this, table.get_iter(pos.second),
|
---|
733 | table.nonempty_end()),
|
---|
734 | true); // true: we did insert
|
---|
735 | }
|
---|
736 | }
|
---|
737 |
|
---|
738 | public:
|
---|
739 | // This is the normal insert routine, used by the outside world
|
---|
740 | pair<iterator, bool> insert(const value_type& obj) {
|
---|
741 | resize_delta(1); // adding an object, grow if need be
|
---|
742 | return insert_noresize(obj);
|
---|
743 | }
|
---|
744 |
|
---|
745 | #ifdef UNDERSTANDS_ITERATOR_TAGS
|
---|
746 | // When inserting a lot at a time, we specialize on the type of iterator
|
---|
747 | template <class InputIterator>
|
---|
748 | void insert(InputIterator f, InputIterator l) {
|
---|
749 | // specializes on iterator type
|
---|
750 | insert(f, l, typename STL_NAMESPACE::iterator_traits<InputIterator>::iterator_category());
|
---|
751 | }
|
---|
752 |
|
---|
753 | // Iterator supports operator-, resize before inserting
|
---|
754 | template <class ForwardIterator>
|
---|
755 | void insert(ForwardIterator f, ForwardIterator l,
|
---|
756 | STL_NAMESPACE::forward_iterator_tag) {
|
---|
757 | size_type n = STL_NAMESPACE::distance(f, l); // TODO(csilvers): standard?
|
---|
758 | resize_delta(n);
|
---|
759 | for ( ; n > 0; --n, ++f)
|
---|
760 | insert_noresize(*f);
|
---|
761 | }
|
---|
762 |
|
---|
763 | // Arbitrary iterator, can't tell how much to resize
|
---|
764 | template <class InputIterator>
|
---|
765 | void insert(InputIterator f, InputIterator l,
|
---|
766 | STL_NAMESPACE::input_iterator_tag) {
|
---|
767 | for ( ; f != l; ++f)
|
---|
768 | insert(*f);
|
---|
769 | }
|
---|
770 | #else
|
---|
771 | template <class InputIterator>
|
---|
772 | void insert(InputIterator f, InputIterator l) {
|
---|
773 | for ( ; f != l; ++f)
|
---|
774 | insert(*f);
|
---|
775 | }
|
---|
776 | #endif
|
---|
777 |
|
---|
778 |
|
---|
779 | // DELETION ROUTINES
|
---|
780 | size_type erase(const key_type& key) {
|
---|
781 | const_iterator pos = find(key); // shrug: shouldn't need to be const
|
---|
782 | if ( pos != end() ) {
|
---|
783 | assert(!test_deleted(pos)); // or find() shouldn't have returned it
|
---|
784 | set_deleted(pos);
|
---|
785 | ++num_deleted;
|
---|
786 | consider_shrink = true; // will think about shrink after next insert
|
---|
787 | return 1; // because we deleted one thing
|
---|
788 | } else {
|
---|
789 | return 0; // because we deleted nothing
|
---|
790 | }
|
---|
791 | }
|
---|
792 |
|
---|
793 | // This is really evil: really it should be iterator, not const_iterator.
|
---|
794 | // But...the only reason keys are const is to allow lookup.
|
---|
795 | // Since that's a moot issue for deleted keys, we allow const_iterators
|
---|
796 | void erase(const_iterator pos) {
|
---|
797 | if ( pos == end() ) return; // sanity check
|
---|
798 | if ( set_deleted(pos) ) { // true if object has been newly deleted
|
---|
799 | ++num_deleted;
|
---|
800 | consider_shrink = true; // will think about shrink after next insert
|
---|
801 | }
|
---|
802 | }
|
---|
803 |
|
---|
804 | void erase(const_iterator f, const_iterator l) {
|
---|
805 | for ( ; f != l; ++f) {
|
---|
806 | if ( set_deleted(f) ) // should always be true
|
---|
807 | ++num_deleted;
|
---|
808 | }
|
---|
809 | consider_shrink = true; // will think about shrink after next insert
|
---|
810 | }
|
---|
811 |
|
---|
812 |
|
---|
813 | // COMPARISON
|
---|
814 | bool operator==(const sparse_hashtable& ht) const {
|
---|
815 | // We really want to check that the hash functions are the same
|
---|
816 | // but alas there's no way to do this. We just hope.
|
---|
817 | return ( num_deleted == ht.num_deleted && table == ht.table );
|
---|
818 | }
|
---|
819 | bool operator!=(const sparse_hashtable& ht) const {
|
---|
820 | return !(*this == ht);
|
---|
821 | }
|
---|
822 |
|
---|
823 |
|
---|
824 | // I/O
|
---|
825 | // We support reading and writing hashtables to disk. NOTE that
|
---|
826 | // this only stores the hashtable metadata, not the stuff you've
|
---|
827 | // actually put in the hashtable! Alas, since I don't know how to
|
---|
828 | // write a hasher or key_equal, you have to make sure everything
|
---|
829 | // but the table is the same. We compact before writing.
|
---|
830 | bool write_metadata(FILE *fp) {
|
---|
831 | squash_deleted(); // so we don't have to worry about delkey
|
---|
832 | return table.write_metadata(fp);
|
---|
833 | }
|
---|
834 |
|
---|
835 | bool read_metadata(FILE *fp) {
|
---|
836 | num_deleted = 0; // since we got rid before writing
|
---|
837 | bool result = table.read_metadata(fp);
|
---|
838 | reset_thresholds();
|
---|
839 | return result;
|
---|
840 | }
|
---|
841 |
|
---|
842 | bool write_nopointer_data(FILE *fp) {
|
---|
843 | return table.write_nopointer_data(fp);
|
---|
844 | }
|
---|
845 |
|
---|
846 | bool read_nopointer_data(FILE *fp) {
|
---|
847 | return table.read_nopointer_data(fp);
|
---|
848 | }
|
---|
849 |
|
---|
850 | private:
|
---|
851 | // The actual data
|
---|
852 | hasher hash; // required by hashed_associative_container
|
---|
853 | key_equal equals;
|
---|
854 | ExtractKey get_key;
|
---|
855 | size_type num_deleted; // how many occupied buckets are marked deleted
|
---|
856 | bool use_deleted; // false until delkey has been set
|
---|
857 | key_type delkey; // which key marks deleted entries
|
---|
858 | sparsetable<value_type> table; // holds num_buckets and num_elements too
|
---|
859 | size_type shrink_threshold; // table.size() * HT_EMPTY_FLT
|
---|
860 | size_type enlarge_threshold; // table.size() * HT_OCCUPANCY_FLT
|
---|
861 | bool consider_shrink; // true if we should try to shrink before next insert
|
---|
862 |
|
---|
863 | void reset_thresholds() {
|
---|
864 | enlarge_threshold = static_cast<size_type>(table.size()*HT_OCCUPANCY_FLT);
|
---|
865 | shrink_threshold = static_cast<size_type>(table.size()*HT_EMPTY_FLT);
|
---|
866 | consider_shrink = false; // whatever caused us to reset already considered
|
---|
867 | }
|
---|
868 | };
|
---|
869 |
|
---|
870 | // We need a global swap as well
|
---|
871 | template <class V, class K, class HF, class ExK, class EqK, class A>
|
---|
872 | inline void swap(sparse_hashtable<V,K,HF,ExK,EqK,A> &x,
|
---|
873 | sparse_hashtable<V,K,HF,ExK,EqK,A> &y) {
|
---|
874 | x.swap(y);
|
---|
875 | }
|
---|
876 |
|
---|
877 | #undef JUMP_
|
---|
878 |
|
---|
879 | template <class V, class K, class HF, class ExK, class EqK, class A>
|
---|
880 | const typename sparse_hashtable<V,K,HF,ExK,EqK,A>::size_type
|
---|
881 | sparse_hashtable<V,K,HF,ExK,EqK,A>::ILLEGAL_BUCKET;
|
---|
882 |
|
---|
883 | // How full we let the table get before we resize. Knuth says .8 is
|
---|
884 | // good -- higher causes us to probe too much, though saves memory
|
---|
885 | template <class V, class K, class HF, class ExK, class EqK, class A>
|
---|
886 | const float sparse_hashtable<V,K,HF,ExK,EqK,A>::HT_OCCUPANCY_FLT = 0.8f;
|
---|
887 |
|
---|
888 | // How empty we let the table get before we resize lower.
|
---|
889 | // It should be less than OCCUPANCY_FLT / 2 or we thrash resizing
|
---|
890 | template <class V, class K, class HF, class ExK, class EqK, class A>
|
---|
891 | const float sparse_hashtable<V,K,HF,ExK,EqK,A>::HT_EMPTY_FLT = 0.4 *
|
---|
892 | sparse_hashtable<V,K,HF,ExK,EqK,A>::HT_OCCUPANCY_FLT;
|
---|
893 |
|
---|
894 | _END_GOOGLE_NAMESPACE_
|
---|
895 |
|
---|
896 | #endif /* _SPARSEHASHTABLE_H_ */
|
---|