115 lines
3.8 KiB
C++
115 lines
3.8 KiB
C++
/*
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* Copyright (C) 2017 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/Atomics.h>
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#include <wtf/FastMalloc.h>
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#include <wtf/HashFunctions.h>
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#include <wtf/Lock.h>
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#include <wtf/Noncopyable.h>
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#include <wtf/Vector.h>
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namespace WTF {
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DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(ConcurrentBuffer);
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// ConcurrentBuffer is suitable for when you plan to store immutable data and sometimes append to it.
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// It supports storing data that is not copy-constructable but bit-copyable.
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template<typename T>
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class ConcurrentBuffer final {
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WTF_MAKE_NONCOPYABLE(ConcurrentBuffer);
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WTF_MAKE_FAST_ALLOCATED;
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public:
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ConcurrentBuffer()
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{
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}
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~ConcurrentBuffer()
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{
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if (Array* array = m_array) {
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for (size_t i = 0; i < array->size; ++i)
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array->data[i].~T();
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}
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for (Array* array : m_allArrays)
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ConcurrentBufferMalloc::free(array);
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}
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// Growing is not concurrent. This assumes you are holding some other lock before you do this.
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void growExact(size_t newSize)
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{
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Array* array = m_array;
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if (array && newSize <= array->size)
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return;
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Array* newArray = createArray(newSize);
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// This allows us to do ConcurrentBuffer<std::unique_ptr<>>.
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// static_cast<void*> avoids triggering -Wclass-memaccess.
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if (array)
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memcpy(static_cast<void*>(newArray->data), array->data, sizeof(T) * array->size);
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for (size_t i = array ? array->size : 0; i < newSize; ++i)
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new (newArray->data + i) T();
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WTF::storeStoreFence();
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m_array = newArray;
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WTF::storeStoreFence();
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m_allArrays.append(newArray);
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}
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void grow(size_t newSize)
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{
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size_t size = m_array ? m_array->size : 0;
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if (newSize <= size)
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return;
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growExact(std::max(newSize, size * 2));
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}
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struct Array {
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size_t size; // This is an immutable size.
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T data[1];
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};
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Array* array() const { return m_array; }
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T& operator[](size_t index) { return m_array->data[index]; }
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const T& operator[](size_t index) const { return m_array->data[index]; }
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private:
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Array* createArray(size_t size)
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{
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Checked<size_t> objectSize = sizeof(T);
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objectSize *= size;
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objectSize += static_cast<size_t>(OBJECT_OFFSETOF(Array, data));
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Array* result = static_cast<Array*>(ConcurrentBufferMalloc::malloc(objectSize));
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result->size = size;
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return result;
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}
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Array* m_array { nullptr };
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Vector<Array*> m_allArrays;
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};
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} // namespace WTF
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