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| 1 // Copyright 2008 the V8 project authors. All rights reserved. | |
| 2 // Redistribution and use in source and binary forms, with or without | |
| 3 // modification, are permitted provided that the following conditions are | |
| 4 // met: | |
| 5 // | |
| 6 // * Redistributions of source code must retain the above copyright | |
| 7 // notice, this list of conditions and the following disclaimer. | |
| 8 // * Redistributions in binary form must reproduce the above | |
| 9 // copyright notice, this list of conditions and the following | |
| 10 // disclaimer in the documentation and/or other materials provided | |
| 11 // with the distribution. | |
| 12 // * Neither the name of Google Inc. nor the names of its | |
| 13 // contributors may be used to endorse or promote products derived | |
| 14 // from this software without specific prior written permission. | |
| 15 // | |
| 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
| 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
| 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
| 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
| 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
| 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 27 | |
| 28 #include "../include/v8stdint.h" | |
| 29 #include "globals.h" | |
| 30 #include "checks.h" | |
| 31 #include "utils.h" | |
| 32 #include "allocation.h" | |
| 33 | |
| 34 #include "hashmap.h" | |
| 35 | |
| 36 namespace v8 { | |
| 37 namespace internal { | |
| 38 | |
| 39 Allocator* HashMap::DefaultAllocator = ::new Allocator(); | |
| 40 | |
| 41 | |
| 42 HashMap::HashMap(MatchFun match, | |
| 43 Allocator* allocator, | |
| 44 uint32_t initial_capacity) { | |
| 45 allocator_ = allocator; | |
| 46 match_ = match; | |
| 47 Initialize(initial_capacity); | |
| 48 } | |
| 49 | |
| 50 | |
| 51 HashMap::~HashMap() { | |
| 52 if (allocator_) { | |
| 53 allocator_->Delete(map_); | |
| 54 } | |
| 55 } | |
| 56 | |
| 57 | |
| 58 HashMap::Entry* HashMap::Lookup(void* key, uint32_t hash, bool insert) { | |
| 59 // Find a matching entry. | |
| 60 Entry* p = Probe(key, hash); | |
| 61 if (p->key != NULL) { | |
| 62 return p; | |
| 63 } | |
| 64 | |
| 65 // No entry found; insert one if necessary. | |
| 66 if (insert) { | |
| 67 p->key = key; | |
| 68 p->value = NULL; | |
| 69 p->hash = hash; | |
| 70 occupancy_++; | |
| 71 | |
| 72 // Grow the map if we reached >= 80% occupancy. | |
| 73 if (occupancy_ + occupancy_/4 >= capacity_) { | |
| 74 Resize(); | |
| 75 p = Probe(key, hash); | |
| 76 } | |
| 77 | |
| 78 return p; | |
| 79 } | |
| 80 | |
| 81 // No entry found and none inserted. | |
| 82 return NULL; | |
| 83 } | |
| 84 | |
| 85 | |
| 86 void HashMap::Remove(void* key, uint32_t hash) { | |
| 87 // Lookup the entry for the key to remove. | |
| 88 Entry* p = Probe(key, hash); | |
| 89 if (p->key == NULL) { | |
| 90 // Key not found nothing to remove. | |
| 91 return; | |
| 92 } | |
| 93 | |
| 94 // To remove an entry we need to ensure that it does not create an empty | |
| 95 // entry that will cause the search for another entry to stop too soon. If all | |
| 96 // the entries between the entry to remove and the next empty slot have their | |
| 97 // initial position inside this interval, clearing the entry to remove will | |
| 98 // not break the search. If, while searching for the next empty entry, an | |
| 99 // entry is encountered which does not have its initial position between the | |
| 100 // entry to remove and the position looked at, then this entry can be moved to | |
| 101 // the place of the entry to remove without breaking the search for it. The | |
| 102 // entry made vacant by this move is now the entry to remove and the process | |
| 103 // starts over. | |
| 104 // Algorithm from http://en.wikipedia.org/wiki/Open_addressing. | |
| 105 | |
| 106 // This guarantees loop termination as there is at least one empty entry so | |
| 107 // eventually the removed entry will have an empty entry after it. | |
| 108 ASSERT(occupancy_ < capacity_); | |
| 109 | |
| 110 // p is the candidate entry to clear. q is used to scan forwards. | |
| 111 Entry* q = p; // Start at the entry to remove. | |
| 112 while (true) { | |
| 113 // Move q to the next entry. | |
| 114 q = q + 1; | |
| 115 if (q == map_end()) { | |
| 116 q = map_; | |
| 117 } | |
| 118 | |
| 119 // All entries between p and q have their initial position between p and q | |
| 120 // and the entry p can be cleared without breaking the search for these | |
| 121 // entries. | |
| 122 if (q->key == NULL) { | |
| 123 break; | |
| 124 } | |
| 125 | |
| 126 // Find the initial position for the entry at position q. | |
| 127 Entry* r = map_ + (q->hash & (capacity_ - 1)); | |
| 128 | |
| 129 // If the entry at position q has its initial position outside the range | |
| 130 // between p and q it can be moved forward to position p and will still be | |
| 131 // found. There is now a new candidate entry for clearing. | |
| 132 if ((q > p && (r <= p || r > q)) || | |
| 133 (q < p && (r <= p && r > q))) { | |
| 134 *p = *q; | |
| 135 p = q; | |
| 136 } | |
| 137 } | |
| 138 | |
| 139 // Clear the entry which is allowed to en emptied. | |
| 140 p->key = NULL; | |
| 141 occupancy_--; | |
| 142 } | |
| 143 | |
| 144 | |
| 145 void HashMap::Clear() { | |
| 146 // Mark all entries as empty. | |
| 147 const Entry* end = map_end(); | |
| 148 for (Entry* p = map_; p < end; p++) { | |
| 149 p->key = NULL; | |
| 150 } | |
| 151 occupancy_ = 0; | |
| 152 } | |
| 153 | |
| 154 | |
| 155 HashMap::Entry* HashMap::Start() const { | |
| 156 return Next(map_ - 1); | |
| 157 } | |
| 158 | |
| 159 | |
| 160 HashMap::Entry* HashMap::Next(Entry* p) const { | |
| 161 const Entry* end = map_end(); | |
| 162 ASSERT(map_ - 1 <= p && p < end); | |
| 163 for (p++; p < end; p++) { | |
| 164 if (p->key != NULL) { | |
| 165 return p; | |
| 166 } | |
| 167 } | |
| 168 return NULL; | |
| 169 } | |
| 170 | |
| 171 | |
| 172 HashMap::Entry* HashMap::Probe(void* key, uint32_t hash) { | |
| 173 ASSERT(key != NULL); | |
| 174 | |
| 175 ASSERT(IsPowerOf2(capacity_)); | |
| 176 Entry* p = map_ + (hash & (capacity_ - 1)); | |
| 177 const Entry* end = map_end(); | |
| 178 ASSERT(map_ <= p && p < end); | |
| 179 | |
| 180 ASSERT(occupancy_ < capacity_); // Guarantees loop termination. | |
| 181 while (p->key != NULL && (hash != p->hash || !match_(key, p->key))) { | |
| 182 p++; | |
| 183 if (p >= end) { | |
| 184 p = map_; | |
| 185 } | |
| 186 } | |
| 187 | |
| 188 return p; | |
| 189 } | |
| 190 | |
| 191 | |
| 192 void HashMap::Initialize(uint32_t capacity) { | |
| 193 ASSERT(IsPowerOf2(capacity)); | |
| 194 map_ = reinterpret_cast<Entry*>(allocator_->New(capacity * sizeof(Entry))); | |
| 195 if (map_ == NULL) { | |
| 196 v8::internal::FatalProcessOutOfMemory("HashMap::Initialize"); | |
| 197 return; | |
| 198 } | |
| 199 capacity_ = capacity; | |
| 200 Clear(); | |
| 201 } | |
| 202 | |
| 203 | |
| 204 void HashMap::Resize() { | |
| 205 Entry* map = map_; | |
| 206 uint32_t n = occupancy_; | |
| 207 | |
| 208 // Allocate larger map. | |
| 209 Initialize(capacity_ * 2); | |
| 210 | |
| 211 // Rehash all current entries. | |
| 212 for (Entry* p = map; n > 0; p++) { | |
| 213 if (p->key != NULL) { | |
| 214 Lookup(p->key, p->hash, true)->value = p->value; | |
| 215 n--; | |
| 216 } | |
| 217 } | |
| 218 | |
| 219 // Delete old map. | |
| 220 allocator_->Delete(map); | |
| 221 } | |
| 222 | |
| 223 | |
| 224 } } // namespace v8::internal | |
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Chromium Code Reviews
Issue 9372106:
Make HashMap a template class to specify the allocation policy. (Closed)
Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/