ager@chromium.org | 9258b6b | 2008-09-11 09:11:10 +0000 | [diff] [blame] | 1 | // Copyright 2008 the V8 project authors. All rights reserved. |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 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 | |
ager@chromium.org | beb2571 | 2010-11-29 08:02:25 +0000 | [diff] [blame] | 28 | #include "../include/v8stdint.h" |
| 29 | #include "globals.h" |
| 30 | #include "checks.h" |
| 31 | #include "utils.h" |
| 32 | #include "allocation.h" |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 33 | |
| 34 | #include "hashmap.h" |
| 35 | |
kasperl@chromium.org | 71affb5 | 2009-05-26 05:44:31 +0000 | [diff] [blame] | 36 | namespace v8 { |
| 37 | namespace internal { |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 38 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 39 | Allocator HashMap::DefaultAllocator; |
| 40 | |
| 41 | |
| 42 | HashMap::HashMap() { |
| 43 | allocator_ = NULL; |
| 44 | match_ = NULL; |
| 45 | } |
| 46 | |
| 47 | |
| 48 | HashMap::HashMap(MatchFun match, |
| 49 | Allocator* allocator, |
| 50 | uint32_t initial_capacity) { |
| 51 | allocator_ = allocator; |
| 52 | match_ = match; |
| 53 | Initialize(initial_capacity); |
| 54 | } |
| 55 | |
| 56 | |
| 57 | HashMap::~HashMap() { |
| 58 | if (allocator_) { |
| 59 | allocator_->Delete(map_); |
| 60 | } |
| 61 | } |
| 62 | |
| 63 | |
| 64 | HashMap::Entry* HashMap::Lookup(void* key, uint32_t hash, bool insert) { |
| 65 | // Find a matching entry. |
| 66 | Entry* p = Probe(key, hash); |
kasperl@chromium.org | b3284ad | 2009-05-18 06:12:45 +0000 | [diff] [blame] | 67 | if (p->key != NULL) { |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 68 | return p; |
| 69 | } |
| 70 | |
| 71 | // No entry found; insert one if necessary. |
| 72 | if (insert) { |
| 73 | p->key = key; |
| 74 | p->value = NULL; |
| 75 | p->hash = hash; |
| 76 | occupancy_++; |
| 77 | |
| 78 | // Grow the map if we reached >= 80% occupancy. |
| 79 | if (occupancy_ + occupancy_/4 >= capacity_) { |
| 80 | Resize(); |
| 81 | p = Probe(key, hash); |
| 82 | } |
| 83 | |
| 84 | return p; |
| 85 | } |
| 86 | |
| 87 | // No entry found and none inserted. |
| 88 | return NULL; |
| 89 | } |
| 90 | |
| 91 | |
kasperl@chromium.org | b3284ad | 2009-05-18 06:12:45 +0000 | [diff] [blame] | 92 | void HashMap::Remove(void* key, uint32_t hash) { |
| 93 | // Lookup the entry for the key to remove. |
sgjesse@chromium.org | 755c5b1 | 2009-05-29 11:04:38 +0000 | [diff] [blame] | 94 | Entry* p = Probe(key, hash); |
kasperl@chromium.org | b3284ad | 2009-05-18 06:12:45 +0000 | [diff] [blame] | 95 | if (p->key == NULL) { |
| 96 | // Key not found nothing to remove. |
| 97 | return; |
| 98 | } |
| 99 | |
| 100 | // To remove an entry we need to ensure that it does not create an empty |
| 101 | // entry that will cause the search for another entry to stop too soon. If all |
| 102 | // the entries between the entry to remove and the next empty slot have their |
| 103 | // initial position inside this interval, clearing the entry to remove will |
| 104 | // not break the search. If, while searching for the next empty entry, an |
| 105 | // entry is encountered which does not have its initial position between the |
| 106 | // entry to remove and the position looked at, then this entry can be moved to |
| 107 | // the place of the entry to remove without breaking the search for it. The |
| 108 | // entry made vacant by this move is now the entry to remove and the process |
| 109 | // starts over. |
| 110 | // Algorithm from http://en.wikipedia.org/wiki/Open_addressing. |
| 111 | |
| 112 | // This guarantees loop termination as there is at least one empty entry so |
| 113 | // eventually the removed entry will have an empty entry after it. |
| 114 | ASSERT(occupancy_ < capacity_); |
| 115 | |
| 116 | // p is the candidate entry to clear. q is used to scan forwards. |
| 117 | Entry* q = p; // Start at the entry to remove. |
| 118 | while (true) { |
| 119 | // Move q to the next entry. |
| 120 | q = q + 1; |
| 121 | if (q == map_end()) { |
| 122 | q = map_; |
| 123 | } |
| 124 | |
| 125 | // All entries between p and q have their initial position between p and q |
| 126 | // and the entry p can be cleared without breaking the search for these |
| 127 | // entries. |
| 128 | if (q->key == NULL) { |
| 129 | break; |
| 130 | } |
| 131 | |
| 132 | // Find the initial position for the entry at position q. |
| 133 | Entry* r = map_ + (q->hash & (capacity_ - 1)); |
| 134 | |
| 135 | // If the entry at position q has its initial position outside the range |
| 136 | // between p and q it can be moved forward to position p and will still be |
| 137 | // found. There is now a new candidate entry for clearing. |
| 138 | if ((q > p && (r <= p || r > q)) || |
| 139 | (q < p && (r <= p && r > q))) { |
| 140 | *p = *q; |
| 141 | p = q; |
| 142 | } |
| 143 | } |
| 144 | |
| 145 | // Clear the entry which is allowed to en emptied. |
| 146 | p->key = NULL; |
| 147 | occupancy_--; |
| 148 | } |
| 149 | |
| 150 | |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 151 | void HashMap::Clear() { |
| 152 | // Mark all entries as empty. |
| 153 | const Entry* end = map_end(); |
| 154 | for (Entry* p = map_; p < end; p++) { |
| 155 | p->key = NULL; |
| 156 | } |
| 157 | occupancy_ = 0; |
| 158 | } |
| 159 | |
| 160 | |
| 161 | HashMap::Entry* HashMap::Start() const { |
| 162 | return Next(map_ - 1); |
| 163 | } |
| 164 | |
| 165 | |
| 166 | HashMap::Entry* HashMap::Next(Entry* p) const { |
| 167 | const Entry* end = map_end(); |
| 168 | ASSERT(map_ - 1 <= p && p < end); |
| 169 | for (p++; p < end; p++) { |
| 170 | if (p->key != NULL) { |
| 171 | return p; |
| 172 | } |
| 173 | } |
| 174 | return NULL; |
| 175 | } |
| 176 | |
| 177 | |
| 178 | HashMap::Entry* HashMap::Probe(void* key, uint32_t hash) { |
| 179 | ASSERT(key != NULL); |
| 180 | |
| 181 | ASSERT(IsPowerOf2(capacity_)); |
| 182 | Entry* p = map_ + (hash & (capacity_ - 1)); |
| 183 | const Entry* end = map_end(); |
| 184 | ASSERT(map_ <= p && p < end); |
| 185 | |
kasperl@chromium.org | b3284ad | 2009-05-18 06:12:45 +0000 | [diff] [blame] | 186 | ASSERT(occupancy_ < capacity_); // Guarantees loop termination. |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 187 | while (p->key != NULL && (hash != p->hash || !match_(key, p->key))) { |
| 188 | p++; |
| 189 | if (p >= end) { |
| 190 | p = map_; |
| 191 | } |
| 192 | } |
| 193 | |
| 194 | return p; |
| 195 | } |
| 196 | |
| 197 | |
| 198 | void HashMap::Initialize(uint32_t capacity) { |
| 199 | ASSERT(IsPowerOf2(capacity)); |
| 200 | map_ = reinterpret_cast<Entry*>(allocator_->New(capacity * sizeof(Entry))); |
kasperl@chromium.org | e959c18 | 2009-07-27 08:59:04 +0000 | [diff] [blame] | 201 | if (map_ == NULL) { |
ager@chromium.org | beb2571 | 2010-11-29 08:02:25 +0000 | [diff] [blame] | 202 | v8::internal::FatalProcessOutOfMemory("HashMap::Initialize"); |
kasperl@chromium.org | e959c18 | 2009-07-27 08:59:04 +0000 | [diff] [blame] | 203 | return; |
| 204 | } |
christian.plesner.hansen | 43d26ec | 2008-07-03 15:10:15 +0000 | [diff] [blame] | 205 | capacity_ = capacity; |
| 206 | Clear(); |
| 207 | } |
| 208 | |
| 209 | |
| 210 | void HashMap::Resize() { |
| 211 | Entry* map = map_; |
| 212 | uint32_t n = occupancy_; |
| 213 | |
| 214 | // Allocate larger map. |
| 215 | Initialize(capacity_ * 2); |
| 216 | |
| 217 | // Rehash all current entries. |
| 218 | for (Entry* p = map; n > 0; p++) { |
| 219 | if (p->key != NULL) { |
| 220 | Lookup(p->key, p->hash, true)->value = p->value; |
| 221 | n--; |
| 222 | } |
| 223 | } |
| 224 | |
| 225 | // Delete old map. |
| 226 | allocator_->Delete(map); |
| 227 | } |
| 228 | |
| 229 | |
| 230 | } } // namespace v8::internal |