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/*
* Copyright (C) 2012 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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.
*/
#pragma once
#include <wtf/OSAllocator.h>
namespace JSC {
// This class implements a simple array class that can be grown by appending items to the end.
// This class is implemented purely in terms of system allocations, with no malloc/free, so that
// it can safely be used from a secondary thread whilst the main thrad is paused (potentially
// holding the fast malloc heap lock).
template<typename T>
class TieredMMapArray {
static const size_t entriesPerBlock = 4096;
public:
TieredMMapArray()
: m_directoryCount(4096)
, m_directory(static_cast<T**>(OSAllocator::reserveAndCommit(m_directoryCount * sizeof(T*))))
, m_size(0)
{
for (size_t block = 0; block < m_directoryCount; ++block)
m_directory[block] = 0;
}
~TieredMMapArray()
{
size_t usedCount = (m_size + (entriesPerBlock - 1)) / entriesPerBlock;
ASSERT(usedCount == m_directoryCount || !m_directory[usedCount]);
for (size_t block = 0; block < usedCount; ++block) {
ASSERT(m_directory[block]);
OSAllocator::decommitAndRelease(m_directory[block], entriesPerBlock * sizeof(T));
}
OSAllocator::decommitAndRelease(m_directory, m_directoryCount * sizeof(T*));
}
T& operator[](size_t index)
{
ASSERT(index < m_size);
size_t block = index / entriesPerBlock;
size_t offset = index % entriesPerBlock;
ASSERT(m_directory[block]);
return m_directory[block][offset];
}
void append(const T& value)
{
// Check if the array is completely full, if so create more capacity in the directory.
if (m_size == m_directoryCount * entriesPerBlock) {
// Reallocate the directory.
size_t oldDirectorySize = m_directoryCount * sizeof(T*);
size_t newDirectorySize = oldDirectorySize * 2;
RELEASE_ASSERT(newDirectorySize < oldDirectorySize);
m_directory = OSAllocator::reallocateCommitted(m_directory, oldDirectorySize, newDirectorySize);
//
size_t newDirectoryCount = m_directoryCount * 2;
for (size_t block = m_directoryCount; block < newDirectoryCount; ++block)
m_directory[block] = 0;
m_directoryCount = newDirectoryCount;
}
size_t index = m_size;
size_t block = index / entriesPerBlock;
size_t offset = index % entriesPerBlock;
if (!offset) {
ASSERT(!m_directory[block]);
m_directory[block] = static_cast<T*>(OSAllocator::reserveAndCommit(entriesPerBlock * sizeof(T)));
}
ASSERT(m_directory[block]);
++m_size;
m_directory[block][offset] = value;
}
size_t size() const { return m_size; }
private:
size_t m_directoryCount;
T** m_directory;
size_t m_size;
};
} // namespace JSC