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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "third_party/blink/renderer/platform/heap/address_cache.h"
#include "third_party/blink/renderer/platform/heap/heap_page.h"
namespace blink {
AddressCache::EnabledScope::EnabledScope(AddressCache* address_cache)
: address_cache_(address_cache) {
address_cache_->FlushIfDirty();
address_cache_->EnableLookup();
}
AddressCache::EnabledScope::~EnabledScope() {
address_cache_->DisableLookup();
}
void AddressCache::Flush() {
if (has_entries_) {
for (size_t i = 0; i < kNumberOfEntries; ++i)
entries_[i] = nullptr;
has_entries_ = false;
}
dirty_ = false;
}
void AddressCache::FlushIfDirty() {
if (dirty_) {
Flush();
dirty_ = false;
}
}
size_t AddressCache::GetHash(Address address) {
size_t value = (reinterpret_cast<size_t>(address) >> kBlinkPageSizeLog2);
value ^= value >> kNumberOfEntriesLog2;
value ^= value >> (kNumberOfEntriesLog2 * 2);
value &= kNumberOfEntries - 1;
return value & ~1; // Returns only even number.
}
bool AddressCache::Lookup(Address address) {
DCHECK(enabled_);
DCHECK(!dirty_);
size_t index = GetHash(address);
DCHECK(!(index & 1));
Address cache_page = RoundToBlinkPageStart(address);
if (entries_[index] == cache_page)
return entries_[index];
if (entries_[index + 1] == cache_page)
return entries_[index + 1];
return false;
}
void AddressCache::AddEntry(Address address) {
has_entries_ = true;
size_t index = GetHash(address);
DCHECK(!(index & 1));
Address cache_page = RoundToBlinkPageStart(address);
entries_[index + 1] = entries_[index];
entries_[index] = cache_page;
}
} // namespace blink
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