/*
 *  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 A mutex-synchronized version of \p unsynchronized_pool_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/pool.h>

#include <mutex>

THRUST_NAMESPACE_BEGIN
namespace mr
{
/*! \addtogroup memory_resources Memory Resources
 *  \ingroup memory_management
 *  \{
 */

/*! A mutex-synchronized version of \p unsynchronized_pool_resource. Uses \p std::mutex, and therefore requires C++11.
 *
 *  \tparam Upstream the type of memory resources that will be used for allocating memory
 */
template <typename Upstream>
struct synchronized_pool_resource : public memory_resource<typename Upstream::pointer>
{
  using unsync_pool = unsynchronized_pool_resource<Upstream>;
  using lock_t      = std::lock_guard<std::mutex>;

  using void_ptr = typename Upstream::pointer;

public:
  /*! Get the default options for a pool. These are meant to be a sensible set of values for many use cases,
   *      and as such, may be tuned in the future. This function is exposed so that creating a set of options that are
   *      just a slight departure from the defaults is easy.
   */
  static pool_options get_default_options()
  {
    return unsync_pool::get_default_options();
  }

  /*! Constructor.
   *
   *  \param upstream the upstream memory resource for allocations
   *  \param options pool options to use
   */
  synchronized_pool_resource(Upstream* upstream, pool_options options = get_default_options())
      : upstream_pool(upstream, options)
  {}

  /*! Constructor. The upstream resource is obtained by calling \p get_global_resource<Upstream>.
   *
   *  \param options pool options to use
   */
  synchronized_pool_resource(pool_options options = get_default_options())
      : upstream_pool(get_global_resource<Upstream>(), options)
  {}

  /*! Releases all held memory to upstream.
   */
  void release()
  {
    lock_t lock(mtx);
    upstream_pool.release();
  }

  [[nodiscard]] virtual void_ptr
  do_allocate(std::size_t bytes, std::size_t alignment = THRUST_MR_DEFAULT_ALIGNMENT) override
  {
    lock_t lock(mtx);
    return upstream_pool.do_allocate(bytes, alignment);
  }

  virtual void do_deallocate(void_ptr p, std::size_t n, std::size_t alignment = THRUST_MR_DEFAULT_ALIGNMENT) override
  {
    lock_t lock(mtx);
    upstream_pool.do_deallocate(p, n, alignment);
  }

private:
  std::mutex mtx;
  unsync_pool upstream_pool;
};

/*! \} // memory_resources
 */
} // namespace mr
THRUST_NAMESPACE_END
