as_pmr_allocator.h

// Copyright 2024 The Pigweed Authors
//
// 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
//
//     https://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.
#pragma once
 
#if __has_include(<memory_resource>)
#include <memory_resource>
namespace pw {
namespace pmr = ::std::pmr;
}  // namespace pw
 
#elif __has_include(<experimental/memory_resource>)
#include <experimental/memory_resource>
namespace pw {
namespace pmr = ::std::experimental::pmr;
}  // namespace pw
 
#else
#error "<memory_resource> is required to use this header!"
#endif  // __has_include(<memory_resource>)
 
#include "pw_status/status_with_size.h"
 
namespace pw {
 
// Forward declaration
class Allocator;
 
namespace allocator {
 
// Forward declaration
class AsPmrAllocator;
 
namespace internal {
 
class MemoryResource final : public pw::pmr::memory_resource {
 public:
  constexpr MemoryResource() = default;
 
  Allocator& allocator() { return *allocator_; }
 
 private:
  friend class ::pw::allocator::AsPmrAllocator;
  void set_allocator(Allocator& allocator) { allocator_ = &allocator; }
 
  void* do_allocate(size_t bytes, size_t alignment) override;
  void do_deallocate(void* p, size_t bytes, size_t alignment) override;
  bool do_is_equal(
      const pw::pmr::memory_resource& other) const noexcept override;
 
  Allocator* allocator_ = nullptr;
};
 
}  // namespace internal
 
class AsPmrAllocator final : public pw::pmr::polymorphic_allocator<std::byte> {
 public:
  using Base = pw::pmr::polymorphic_allocator<std::byte>;
 
  AsPmrAllocator(Allocator& allocator) : Base(&memory_resource_) {
    memory_resource_.set_allocator(allocator);
  }
 
  Allocator& allocator() { return memory_resource_.allocator(); }
 
 private:
  internal::MemoryResource memory_resource_;
};
 
}  // namespace allocator
}  // namespace pw