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/*
* Copyright 2018 NVIDIA Corporation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*! \file
* \brief Global operator new-based memory resource.
*/
#pragma once
#include <thrust/detail/config.h>
#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
# pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
# pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
# pragma system_header
#endif // no system header
#include <thrust/mr/memory_resource.h>
THRUST_NAMESPACE_BEGIN
namespace mr
{
/** \addtogroup memory_resources Memory Resources
* \ingroup memory_management
* \{
*/
/*! A memory resource that uses global operators new and delete to allocate and deallocate memory. Uses alignment-enabled
* overloads when available, otherwise uses regular overloads and implements alignment requirements by itself.
*/
class new_delete_resource final : public memory_resource<>
{
public:
void * do_allocate(std::size_t bytes, std::size_t alignment = THRUST_MR_DEFAULT_ALIGNMENT) override
{
#if defined(__cpp_aligned_new)
return ::operator new(bytes, std::align_val_t(alignment));
#else
// allocate memory for bytes, plus potential alignment correction,
// plus store of the correction offset
void * p = ::operator new(bytes + alignment + sizeof(std::size_t));
std::size_t ptr_int = reinterpret_cast<std::size_t>(p);
// calculate the offset, i.e. how many bytes of correction was necessary
// to get an aligned pointer
std::size_t offset = (ptr_int % alignment) ? (alignment - ptr_int % alignment) : 0;
// calculate the return pointer
char * ptr = static_cast<char *>(p) + offset;
// store the offset right after the actually returned value
std::size_t * offset_store = reinterpret_cast<std::size_t *>(ptr + bytes);
*offset_store = offset;
return static_cast<void *>(ptr);
#endif
}
void do_deallocate(void * p, std::size_t bytes, std::size_t alignment = THRUST_MR_DEFAULT_ALIGNMENT) override
{
#if defined(__cpp_aligned_new)
# if defined(__cpp_sized_deallocation)
::operator delete(p, bytes, std::align_val_t(alignment));
# else
(void)bytes;
::operator delete(p, std::align_val_t(alignment));
# endif
#else
(void)alignment;
char * ptr = static_cast<char *>(p);
// calculate where the offset is stored
std::size_t * offset = reinterpret_cast<std::size_t *>(ptr + bytes);
// calculate the original pointer
p = static_cast<void *>(ptr - *offset);
::operator delete(p);
#endif
}
};
/*! \} // memory_resources
*/
} // end mr
THRUST_NAMESPACE_END
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