115 lines
3.4 KiB
C++
115 lines
3.4 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// AlignedMemory is a POD type that gives you a portable way to specify static
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// or local stack data of a given alignment and size. For example, if you need
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// static storage for a class, but you want manual control over when the object
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// is constructed and destructed (you don't want static initialization and
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// destruction), use AlignedMemory:
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//
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// static AlignedMemory<sizeof(MyClass), ALIGNOF(MyClass)> my_class;
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//
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// // ... at runtime:
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// new(my_class.void_data()) MyClass();
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//
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// // ... use it:
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// MyClass* mc = my_class.data_as<MyClass>();
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//
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// // ... later, to destruct my_class:
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// my_class.data_as<MyClass>()->MyClass::~MyClass();
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//
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// Alternatively, a runtime sized aligned allocation can be created:
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//
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// float* my_array = static_cast<float*>(AlignedAlloc(size, alignment));
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//
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// // ... later, to release the memory:
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// AlignedFree(my_array);
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//
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// Or using scoped_ptr_malloc:
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//
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// scoped_ptr_malloc<float, ScopedPtrAlignedFree> my_array(
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// static_cast<float*>(AlignedAlloc(size, alignment)));
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#ifndef BASE_MEMORY_ALIGNED_MEMORY_H_
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#define BASE_MEMORY_ALIGNED_MEMORY_H_
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#include "base/base_export.h"
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#include "base/basictypes.h"
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#include "base/compiler_specific.h"
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#if defined(COMPILER_MSVC)
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#include <malloc.h>
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#else
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#include <stdlib.h>
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#endif
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namespace base {
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// AlignedMemory is specialized for all supported alignments.
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// Make sure we get a compiler error if someone uses an unsupported alignment.
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template <size_t Size, size_t ByteAlignment>
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struct AlignedMemory {};
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#define BASE_DECL_ALIGNED_MEMORY(byte_alignment) \
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template <size_t Size> \
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class AlignedMemory<Size, byte_alignment> { \
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public: \
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ALIGNAS(byte_alignment) uint8 data_[Size]; \
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void* void_data() { return static_cast<void*>(data_); } \
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const void* void_data() const { \
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return static_cast<const void*>(data_); \
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} \
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template<typename Type> \
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Type* data_as() { return static_cast<Type*>(void_data()); } \
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template<typename Type> \
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const Type* data_as() const { \
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return static_cast<const Type*>(void_data()); \
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} \
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private: \
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void* operator new(size_t); \
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void operator delete(void*); \
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}
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// Specialization for all alignments is required because MSVC (as of VS 2008)
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// does not understand ALIGNAS(ALIGNOF(Type)) or ALIGNAS(template_param).
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// Greater than 4096 alignment is not supported by some compilers, so 4096 is
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// the maximum specified here.
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BASE_DECL_ALIGNED_MEMORY(1);
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BASE_DECL_ALIGNED_MEMORY(2);
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BASE_DECL_ALIGNED_MEMORY(4);
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BASE_DECL_ALIGNED_MEMORY(8);
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BASE_DECL_ALIGNED_MEMORY(16);
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BASE_DECL_ALIGNED_MEMORY(32);
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BASE_DECL_ALIGNED_MEMORY(64);
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BASE_DECL_ALIGNED_MEMORY(128);
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BASE_DECL_ALIGNED_MEMORY(256);
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BASE_DECL_ALIGNED_MEMORY(512);
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BASE_DECL_ALIGNED_MEMORY(1024);
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BASE_DECL_ALIGNED_MEMORY(2048);
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BASE_DECL_ALIGNED_MEMORY(4096);
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#undef BASE_DECL_ALIGNED_MEMORY
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BASE_EXPORT void* AlignedAlloc(size_t size, size_t alignment);
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inline void AlignedFree(void* ptr) {
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#if defined(COMPILER_MSVC)
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_aligned_free(ptr);
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#else
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free(ptr);
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#endif
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}
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// Helper class for use with scoped_ptr_malloc.
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class BASE_EXPORT ScopedPtrAlignedFree {
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public:
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inline void operator()(void* ptr) const {
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AlignedFree(ptr);
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}
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};
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} // namespace base
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#endif // BASE_MEMORY_ALIGNED_MEMORY_H_
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