mirror of https://github.com/lukechilds/node.git
isaacs
13 years ago
81 changed files with 6248 additions and 824 deletions
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// Copyright 2008 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "../include/v8stdint.h" |
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#include "globals.h" |
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#include "checks.h" |
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#include "utils.h" |
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#include "allocation.h" |
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#include "hashmap.h" |
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namespace v8 { |
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namespace internal { |
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Allocator* HashMap::DefaultAllocator = ::new Allocator(); |
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HashMap::HashMap(MatchFun match, |
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Allocator* allocator, |
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uint32_t initial_capacity) { |
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allocator_ = allocator; |
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match_ = match; |
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Initialize(initial_capacity); |
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} |
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HashMap::~HashMap() { |
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if (allocator_) { |
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allocator_->Delete(map_); |
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} |
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} |
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HashMap::Entry* HashMap::Lookup(void* key, uint32_t hash, bool insert) { |
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// Find a matching entry.
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Entry* p = Probe(key, hash); |
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if (p->key != NULL) { |
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return p; |
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} |
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// No entry found; insert one if necessary.
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if (insert) { |
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p->key = key; |
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p->value = NULL; |
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p->hash = hash; |
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occupancy_++; |
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// Grow the map if we reached >= 80% occupancy.
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if (occupancy_ + occupancy_/4 >= capacity_) { |
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Resize(); |
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p = Probe(key, hash); |
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} |
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return p; |
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} |
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// No entry found and none inserted.
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return NULL; |
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} |
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void HashMap::Remove(void* key, uint32_t hash) { |
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// Lookup the entry for the key to remove.
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Entry* p = Probe(key, hash); |
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if (p->key == NULL) { |
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// Key not found nothing to remove.
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return; |
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} |
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// To remove an entry we need to ensure that it does not create an empty
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// entry that will cause the search for another entry to stop too soon. If all
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// the entries between the entry to remove and the next empty slot have their
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// initial position inside this interval, clearing the entry to remove will
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// not break the search. If, while searching for the next empty entry, an
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// entry is encountered which does not have its initial position between the
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// entry to remove and the position looked at, then this entry can be moved to
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// the place of the entry to remove without breaking the search for it. The
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// entry made vacant by this move is now the entry to remove and the process
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// starts over.
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// Algorithm from http://en.wikipedia.org/wiki/Open_addressing.
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// This guarantees loop termination as there is at least one empty entry so
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// eventually the removed entry will have an empty entry after it.
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ASSERT(occupancy_ < capacity_); |
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// p is the candidate entry to clear. q is used to scan forwards.
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Entry* q = p; // Start at the entry to remove.
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while (true) { |
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// Move q to the next entry.
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q = q + 1; |
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if (q == map_end()) { |
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q = map_; |
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} |
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// All entries between p and q have their initial position between p and q
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// and the entry p can be cleared without breaking the search for these
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// entries.
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if (q->key == NULL) { |
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break; |
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} |
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// Find the initial position for the entry at position q.
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Entry* r = map_ + (q->hash & (capacity_ - 1)); |
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// If the entry at position q has its initial position outside the range
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// between p and q it can be moved forward to position p and will still be
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// found. There is now a new candidate entry for clearing.
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if ((q > p && (r <= p || r > q)) || |
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(q < p && (r <= p && r > q))) { |
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*p = *q; |
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p = q; |
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} |
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} |
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// Clear the entry which is allowed to en emptied.
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p->key = NULL; |
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occupancy_--; |
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} |
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void HashMap::Clear() { |
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// Mark all entries as empty.
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const Entry* end = map_end(); |
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for (Entry* p = map_; p < end; p++) { |
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p->key = NULL; |
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} |
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occupancy_ = 0; |
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} |
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HashMap::Entry* HashMap::Start() const { |
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return Next(map_ - 1); |
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} |
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HashMap::Entry* HashMap::Next(Entry* p) const { |
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const Entry* end = map_end(); |
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ASSERT(map_ - 1 <= p && p < end); |
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for (p++; p < end; p++) { |
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if (p->key != NULL) { |
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return p; |
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} |
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} |
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return NULL; |
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} |
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HashMap::Entry* HashMap::Probe(void* key, uint32_t hash) { |
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ASSERT(key != NULL); |
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ASSERT(IsPowerOf2(capacity_)); |
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Entry* p = map_ + (hash & (capacity_ - 1)); |
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const Entry* end = map_end(); |
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ASSERT(map_ <= p && p < end); |
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ASSERT(occupancy_ < capacity_); // Guarantees loop termination.
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while (p->key != NULL && (hash != p->hash || !match_(key, p->key))) { |
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p++; |
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if (p >= end) { |
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p = map_; |
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} |
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} |
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return p; |
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} |
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void HashMap::Initialize(uint32_t capacity) { |
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ASSERT(IsPowerOf2(capacity)); |
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map_ = reinterpret_cast<Entry*>(allocator_->New(capacity * sizeof(Entry))); |
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if (map_ == NULL) { |
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v8::internal::FatalProcessOutOfMemory("HashMap::Initialize"); |
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return; |
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} |
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capacity_ = capacity; |
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Clear(); |
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} |
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void HashMap::Resize() { |
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Entry* map = map_; |
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uint32_t n = occupancy_; |
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// Allocate larger map.
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Initialize(capacity_ * 2); |
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// Rehash all current entries.
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for (Entry* p = map; n > 0; p++) { |
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if (p->key != NULL) { |
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Lookup(p->key, p->hash, true)->value = p->value; |
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n--; |
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} |
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} |
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// Delete old map.
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allocator_->Delete(map); |
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} |
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} } // namespace v8::internal
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