1/* 2 * Copyright (C) 2012 Apple Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR 17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26#ifndef TieredMMapArray_h 27#define TieredMMapArray_h 28 29#include <wtf/OSAllocator.h> 30 31namespace JSC { 32 33// This class implements a simple array class that can be grown by appending items to the end. 34// This class is implemented purely in terms of system allocations, with no malloc/free, so that 35// it can safely be used from a secondary thread whilst the main thrad is paused (potentially 36// holding the fast malloc heap lock). 37template<typename T> 38class TieredMMapArray { 39 static const size_t entriesPerBlock = 4096; 40 41public: 42 TieredMMapArray() 43 : m_directoryCount(4096) 44 , m_directory(static_cast<T**>(OSAllocator::reserveAndCommit(m_directoryCount * sizeof(T*)))) 45 , m_size(0) 46 { 47 for (size_t block = 0; block < m_directoryCount; ++block) 48 m_directory[block] = 0; 49 } 50 51 ~TieredMMapArray() 52 { 53 size_t usedCount = (m_size + (entriesPerBlock - 1)) / entriesPerBlock; 54 ASSERT(usedCount == m_directoryCount || !m_directory[usedCount]); 55 56 for (size_t block = 0; block < usedCount; ++block) { 57 ASSERT(m_directory[block]); 58 OSAllocator::decommitAndRelease(m_directory[block], entriesPerBlock * sizeof(T)); 59 } 60 61 OSAllocator::decommitAndRelease(m_directory, m_directoryCount * sizeof(T*)); 62 } 63 64 T& operator[](size_t index) 65 { 66 ASSERT(index < m_size); 67 size_t block = index / entriesPerBlock; 68 size_t offset = index % entriesPerBlock; 69 70 ASSERT(m_directory[block]); 71 return m_directory[block][offset]; 72 } 73 74 void append(const T& value) 75 { 76 // Check if the array is completely full, if so create more capacity in the directory. 77 if (m_size == m_directoryCount * entriesPerBlock) { 78 // Reallocate the directory. 79 size_t oldDirectorySize = m_directoryCount * sizeof(T*); 80 size_t newDirectorySize = oldDirectorySize * 2; 81 RELEASE_ASSERT(newDirectorySize < oldDirectorySize); 82 m_directory = OSAllocator::reallocateCommitted(m_directory, oldDirectorySize, newDirectorySize); 83 84 // 85 size_t newDirectoryCount = m_directoryCount * 2; 86 for (size_t block = m_directoryCount; block < newDirectoryCount; ++block) 87 m_directory[block] = 0; 88 m_directoryCount = newDirectoryCount; 89 } 90 91 size_t index = m_size; 92 size_t block = index / entriesPerBlock; 93 size_t offset = index % entriesPerBlock; 94 95 if (!offset) { 96 ASSERT(!m_directory[block]); 97 m_directory[block] = static_cast<T*>(OSAllocator::reserveAndCommit(entriesPerBlock * sizeof(T))); 98 } 99 100 ASSERT(m_directory[block]); 101 ++m_size; 102 m_directory[block][offset] = value; 103 } 104 105 size_t size() const { return m_size; } 106 107private: 108 size_t m_directoryCount; 109 T** m_directory; 110 size_t m_size; 111}; 112 113} 114 115#endif // TieredMMapArray_h 116 117