| // Copyright 2008 the V8 project authors. All rights reserved. |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are |
| // met: |
| // |
| // * Redistributions of source code must retain the above copyright |
| // notice, this list of conditions and the following disclaimer. |
| // * Redistributions in binary form must reproduce the above |
| // copyright notice, this list of conditions and the following |
| // disclaimer in the documentation and/or other materials provided |
| // with the distribution. |
| // * Neither the name of Google Inc. nor the names of its |
| // contributors may be used to endorse or promote products derived |
| // from this software without specific prior written permission. |
| // |
| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| #include "v8.h" |
| |
| #include "hashmap.h" |
| |
| namespace v8 { |
| namespace internal { |
| |
| Allocator HashMap::DefaultAllocator; |
| |
| |
| HashMap::HashMap() { |
| allocator_ = NULL; |
| match_ = NULL; |
| } |
| |
| |
| HashMap::HashMap(MatchFun match, |
| Allocator* allocator, |
| uint32_t initial_capacity) { |
| allocator_ = allocator; |
| match_ = match; |
| Initialize(initial_capacity); |
| } |
| |
| |
| HashMap::~HashMap() { |
| if (allocator_) { |
| allocator_->Delete(map_); |
| } |
| } |
| |
| |
| HashMap::Entry* HashMap::Lookup(void* key, uint32_t hash, bool insert) { |
| // Find a matching entry. |
| Entry* p = Probe(key, hash); |
| if (p->key != NULL) { |
| return p; |
| } |
| |
| // No entry found; insert one if necessary. |
| if (insert) { |
| p->key = key; |
| p->value = NULL; |
| p->hash = hash; |
| occupancy_++; |
| |
| // Grow the map if we reached >= 80% occupancy. |
| if (occupancy_ + occupancy_/4 >= capacity_) { |
| Resize(); |
| p = Probe(key, hash); |
| } |
| |
| return p; |
| } |
| |
| // No entry found and none inserted. |
| return NULL; |
| } |
| |
| |
| void HashMap::Remove(void* key, uint32_t hash) { |
| // Lookup the entry for the key to remove. |
| Entry* p = Probe(key, hash); |
| if (p->key == NULL) { |
| // Key not found nothing to remove. |
| return; |
| } |
| |
| // To remove an entry we need to ensure that it does not create an empty |
| // entry that will cause the search for another entry to stop too soon. If all |
| // the entries between the entry to remove and the next empty slot have their |
| // initial position inside this interval, clearing the entry to remove will |
| // not break the search. If, while searching for the next empty entry, an |
| // entry is encountered which does not have its initial position between the |
| // entry to remove and the position looked at, then this entry can be moved to |
| // the place of the entry to remove without breaking the search for it. The |
| // entry made vacant by this move is now the entry to remove and the process |
| // starts over. |
| // Algorithm from http://en.wikipedia.org/wiki/Open_addressing. |
| |
| // This guarantees loop termination as there is at least one empty entry so |
| // eventually the removed entry will have an empty entry after it. |
| ASSERT(occupancy_ < capacity_); |
| |
| // p is the candidate entry to clear. q is used to scan forwards. |
| Entry* q = p; // Start at the entry to remove. |
| while (true) { |
| // Move q to the next entry. |
| q = q + 1; |
| if (q == map_end()) { |
| q = map_; |
| } |
| |
| // All entries between p and q have their initial position between p and q |
| // and the entry p can be cleared without breaking the search for these |
| // entries. |
| if (q->key == NULL) { |
| break; |
| } |
| |
| // Find the initial position for the entry at position q. |
| Entry* r = map_ + (q->hash & (capacity_ - 1)); |
| |
| // If the entry at position q has its initial position outside the range |
| // between p and q it can be moved forward to position p and will still be |
| // found. There is now a new candidate entry for clearing. |
| if ((q > p && (r <= p || r > q)) || |
| (q < p && (r <= p && r > q))) { |
| *p = *q; |
| p = q; |
| } |
| } |
| |
| // Clear the entry which is allowed to en emptied. |
| p->key = NULL; |
| occupancy_--; |
| } |
| |
| |
| void HashMap::Clear() { |
| // Mark all entries as empty. |
| const Entry* end = map_end(); |
| for (Entry* p = map_; p < end; p++) { |
| p->key = NULL; |
| } |
| occupancy_ = 0; |
| } |
| |
| |
| HashMap::Entry* HashMap::Start() const { |
| return Next(map_ - 1); |
| } |
| |
| |
| HashMap::Entry* HashMap::Next(Entry* p) const { |
| const Entry* end = map_end(); |
| ASSERT(map_ - 1 <= p && p < end); |
| for (p++; p < end; p++) { |
| if (p->key != NULL) { |
| return p; |
| } |
| } |
| return NULL; |
| } |
| |
| |
| HashMap::Entry* HashMap::Probe(void* key, uint32_t hash) { |
| ASSERT(key != NULL); |
| |
| ASSERT(IsPowerOf2(capacity_)); |
| Entry* p = map_ + (hash & (capacity_ - 1)); |
| const Entry* end = map_end(); |
| ASSERT(map_ <= p && p < end); |
| |
| ASSERT(occupancy_ < capacity_); // Guarantees loop termination. |
| while (p->key != NULL && (hash != p->hash || !match_(key, p->key))) { |
| p++; |
| if (p >= end) { |
| p = map_; |
| } |
| } |
| |
| return p; |
| } |
| |
| |
| void HashMap::Initialize(uint32_t capacity) { |
| ASSERT(IsPowerOf2(capacity)); |
| map_ = reinterpret_cast<Entry*>(allocator_->New(capacity * sizeof(Entry))); |
| if (map_ == NULL) V8::FatalProcessOutOfMemory("HashMap::Initialize"); |
| capacity_ = capacity; |
| Clear(); |
| } |
| |
| |
| void HashMap::Resize() { |
| Entry* map = map_; |
| uint32_t n = occupancy_; |
| |
| // Allocate larger map. |
| Initialize(capacity_ * 2); |
| |
| // Rehash all current entries. |
| for (Entry* p = map; n > 0; p++) { |
| if (p->key != NULL) { |
| Lookup(p->key, p->hash, true)->value = p->value; |
| n--; |
| } |
| } |
| |
| // Delete old map. |
| allocator_->Delete(map); |
| } |
| |
| |
| } } // namespace v8::internal |