mirror of
https://github.com/darlinghq/darling-JavaScriptCore.git
synced 2024-11-23 04:09:40 +00:00
113 lines
4.1 KiB
C++
113 lines
4.1 KiB
C++
/*
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* Copyright (C) 2012 Apple Inc. All rights reserved.
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*
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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
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* are met:
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* 1. 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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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* 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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*/
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#pragma once
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#include <wtf/OSAllocator.h>
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namespace JSC {
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// This class implements a simple array class that can be grown by appending items to the end.
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// This class is implemented purely in terms of system allocations, with no malloc/free, so that
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// it can safely be used from a secondary thread whilst the main thrad is paused (potentially
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// holding the fast malloc heap lock).
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template<typename T>
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class TieredMMapArray {
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static const size_t entriesPerBlock = 4096;
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public:
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TieredMMapArray()
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: m_directoryCount(4096)
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, m_directory(static_cast<T**>(OSAllocator::reserveAndCommit(m_directoryCount * sizeof(T*))))
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, m_size(0)
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{
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for (size_t block = 0; block < m_directoryCount; ++block)
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m_directory[block] = 0;
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}
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~TieredMMapArray()
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{
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size_t usedCount = (m_size + (entriesPerBlock - 1)) / entriesPerBlock;
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ASSERT(usedCount == m_directoryCount || !m_directory[usedCount]);
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for (size_t block = 0; block < usedCount; ++block) {
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ASSERT(m_directory[block]);
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OSAllocator::decommitAndRelease(m_directory[block], entriesPerBlock * sizeof(T));
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}
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OSAllocator::decommitAndRelease(m_directory, m_directoryCount * sizeof(T*));
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}
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T& operator[](size_t index)
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{
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ASSERT(index < m_size);
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size_t block = index / entriesPerBlock;
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size_t offset = index % entriesPerBlock;
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ASSERT(m_directory[block]);
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return m_directory[block][offset];
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}
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void append(const T& value)
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{
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// Check if the array is completely full, if so create more capacity in the directory.
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if (m_size == m_directoryCount * entriesPerBlock) {
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// Reallocate the directory.
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size_t oldDirectorySize = m_directoryCount * sizeof(T*);
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size_t newDirectorySize = oldDirectorySize * 2;
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RELEASE_ASSERT(newDirectorySize < oldDirectorySize);
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m_directory = OSAllocator::reallocateCommitted(m_directory, oldDirectorySize, newDirectorySize);
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//
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size_t newDirectoryCount = m_directoryCount * 2;
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for (size_t block = m_directoryCount; block < newDirectoryCount; ++block)
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m_directory[block] = 0;
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m_directoryCount = newDirectoryCount;
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}
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size_t index = m_size;
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size_t block = index / entriesPerBlock;
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size_t offset = index % entriesPerBlock;
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if (!offset) {
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ASSERT(!m_directory[block]);
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m_directory[block] = static_cast<T*>(OSAllocator::reserveAndCommit(entriesPerBlock * sizeof(T)));
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}
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ASSERT(m_directory[block]);
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++m_size;
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m_directory[block][offset] = value;
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}
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size_t size() const { return m_size; }
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private:
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size_t m_directoryCount;
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T** m_directory;
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size_t m_size;
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};
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} // namespace JSC
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