126 lines
4.8 KiB
C++
126 lines
4.8 KiB
C++
/*
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* Copyright (C) 2018 Yusuke Suzuki <utatane.tea@gmail.com>. 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. AND ITS CONTRIBUTORS ``AS IS''
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include <wtf/CheckedArithmetic.h>
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#include <wtf/FastMalloc.h>
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#include <wtf/Vector.h>
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namespace WTF {
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DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(UniqueArray);
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DECLARE_ALLOCATOR_WITH_HEAP_IDENTIFIER(UniqueArrayElement);
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template<bool isTriviallyDestructible, typename T> struct UniqueArrayMaker;
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template<typename T>
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struct UniqueArrayFree {
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static_assert(std::is_trivially_destructible<T>::value, "");
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void operator()(T* pointer) const
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{
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UniqueArrayMalloc::free(const_cast<typename std::remove_cv<T>::type*>(pointer));
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}
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};
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template<typename T>
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struct UniqueArrayFree<T[]> {
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static_assert(std::is_trivially_destructible<T>::value, "");
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void operator()(T* pointer) const
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{
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UniqueArrayMalloc::free(const_cast<typename std::remove_cv<T>::type*>(pointer));
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}
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};
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template<typename T>
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struct UniqueArrayMaker<true, T> {
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using ResultType = typename std::unique_ptr<T[], UniqueArrayFree<T[]>>;
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static ResultType make(size_t size)
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{
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// C++ `new T[N]` stores its `N` to somewhere. Otherwise, `delete []` cannot destroy
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// these N elements. But we do not want to increase the size of allocated memory.
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// If it is acceptable, we can just use Vector<T> instead. So this UniqueArray<T> only
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// accepts the type T which has a trivial destructor. This allows us to skip calling
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// destructors for N elements. And this allows UniqueArray<T> not to store its N size.
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static_assert(std::is_trivially_destructible<T>::value, "");
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// Do not use placement new like `new (storage) T[size]()`. `new T[size]()` requires
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// larger storage than the `sizeof(T) * size` storage since it want to store `size`
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// to somewhere.
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T* storage = static_cast<T*>(UniqueArrayMalloc::malloc(Checked<size_t>(sizeof(T)) * size));
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VectorTypeOperations<T>::initialize(storage, storage + size);
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return ResultType(storage);
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}
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};
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template<typename T>
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struct UniqueArrayMaker<false, T> {
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// Since we do not know how to store/retrieve N size to/from allocated memory when calling new [] and delete [],
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// we use new [] and delete [] operators simply. We create UniqueArrayElement container for the type T.
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// UniqueArrayElement has new [] and delete [] operators for FastMalloc. We allocate UniqueArrayElement[] and cast
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// it to T[]. When deleting, the custom deleter casts T[] to UniqueArrayElement[] and deletes it.
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class UniqueArrayElement {
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WTF_MAKE_FAST_ALLOCATED_WITH_HEAP_IDENTIFIER(UniqueArrayElement);
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public:
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struct Deleter {
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void operator()(T* pointer)
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{
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delete [] bitwise_cast<UniqueArrayElement*>(pointer);
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};
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};
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UniqueArrayElement() = default;
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T value { };
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};
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static_assert(sizeof(T) == sizeof(UniqueArrayElement), "");
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using ResultType = typename std::unique_ptr<T[], typename UniqueArrayElement::Deleter>;
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static ResultType make(size_t size)
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{
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return ResultType(bitwise_cast<T*>(new UniqueArrayElement[size]()));
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}
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};
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template<typename T>
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using UniqueArray = typename UniqueArrayMaker<std::is_trivially_destructible<T>::value, T>::ResultType;
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template<typename T>
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UniqueArray<T> makeUniqueArray(size_t size)
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{
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static_assert(std::is_same<typename std::remove_extent<T>::type, T>::value, "");
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return UniqueArrayMaker<std::is_trivially_destructible<T>::value, T>::make(size);
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}
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} // namespace WTF
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using WTF::UniqueArray;
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using WTF::makeUniqueArray;
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