deallocator.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
 
#include "pw_allocator/capability.h"
#include "pw_allocator/layout.h"
#include "pw_allocator/unique_ptr.h"
#include "pw_result/result.h"
#include "pw_status/status.h"
#include "pw_status/status_with_size.h"
 
namespace pw {
 
class Deallocator {
 protected:
  // Alias types and variables needed for SFINAE below.
  template <typename T>
  static constexpr bool is_bounded_array_v =
      allocator::internal::is_bounded_array_v<T>;
 
  template <typename T>
  static constexpr bool is_unbounded_array_v =
      allocator::internal::is_unbounded_array_v<T>;
 
 public:
  using Capabilities = allocator::Capabilities;
  using Capability = allocator::Capability;
  using Layout = allocator::Layout;
 
  virtual ~Deallocator() = default;
 
  constexpr const Capabilities& capabilities() const { return capabilities_; }
 
  bool HasCapability(Capability capability) const {
    return capabilities_.has(capability);
  }
 
  void Deallocate(void* ptr) {
    if (ptr != nullptr) {
      DoDeallocate(ptr);
    }
  }
 
  void Deallocate(void* ptr, Layout layout) {
    if (ptr != nullptr) {
      DoDeallocate(ptr, layout);
    }
  }
 
  template <typename T>
  void Delete(T* ptr) {
    if (!capabilities_.has(Capability::kSkipsDestroy)) {
      std::destroy_at(ptr);
    }
    Deallocate(ptr);
  }
 
  StatusWithSize GetCapacity() const {
    auto result = DoGetInfo(InfoType::kCapacity, nullptr);
    return StatusWithSize(result.status(), Layout::Unwrap(result).size());
  }
 
  bool IsEqual(const Deallocator& other) const { return this == &other; }
 
  // See WrapUnique below. Disallow calls with explicitly-sized array types like
  // `T[kN]`.
  template <typename T,
            int&... kExplicitGuard,
            std::enable_if_t<is_bounded_array_v<T>, int> = 0,
            typename... Args>
  void WrapUnique(Args&&...) = delete;
 
 protected:
  constexpr Deallocator() = default;
 
  explicit constexpr Deallocator(const Capabilities& capabilities)
      : capabilities_(capabilities) {}
 
  template <typename T, std::enable_if_t<!std::is_array_v<T>, int> = 0>
  [[nodiscard]] UniquePtr<T> WrapUnique(T* ptr) {
    return UniquePtr<T>(ptr, this);
  }
 
  template <typename T,
            int&... kExplicitGuard,
            typename ElementType = std::remove_extent_t<T>,
            std::enable_if_t<is_unbounded_array_v<T>, int> = 0>
  [[nodiscard]] UniquePtr<T> WrapUnique(ElementType* ptr, size_t size) {
    return UniquePtr<T>(ptr, size, this);
  }
 
  template <typename T>
  [[nodiscard]] UniquePtr<T[]> WrapUniqueArray(T* ptr, size_t size) {
    return WrapUnique<T[]>(ptr, size);
  }
 
  enum class InfoType {
    kRequestedLayoutOf,
 
 
    kUsableLayoutOf,
 
    kAllocatedLayoutOf,
 
    kCapacity,
 
    kRecognizes,
  };
 
  Result<Layout> GetInfo(InfoType info_type, const void* ptr) const {
    return DoGetInfo(info_type, ptr);
  }
 
  static Result<Layout> GetInfo(const Deallocator& deallocator,
                                InfoType info_type,
                                const void* ptr) {
    return deallocator.DoGetInfo(info_type, ptr);
  }
 
  Result<Layout> GetRequestedLayout(const void* ptr) const {
    return DoGetInfo(InfoType::kRequestedLayoutOf, ptr);
  }
 
  static Result<Layout> GetRequestedLayout(const Deallocator& deallocator,
                                           const void* ptr) {
    return deallocator.GetRequestedLayout(ptr);
  }
 
  Result<Layout> GetUsableLayout(const void* ptr) const {
    return DoGetInfo(InfoType::kUsableLayoutOf, ptr);
  }
 
  static Result<Layout> GetUsableLayout(const Deallocator& deallocator,
                                        const void* ptr) {
    return deallocator.GetUsableLayout(ptr);
  }
 
  Result<Layout> GetAllocatedLayout(const void* ptr) const {
    return DoGetInfo(InfoType::kAllocatedLayoutOf, ptr);
  }
 
  static Result<Layout> GetAllocatedLayout(const Deallocator& deallocator,
                                           const void* ptr) {
    return deallocator.GetAllocatedLayout(ptr);
  }
 
  bool Recognizes(const void* ptr) const {
    return DoGetInfo(InfoType::kRecognizes, ptr).ok();
  }
 
  static bool Recognizes(const Deallocator& deallocator, const void* ptr) {
    return deallocator.Recognizes(ptr);
  }
 
 private:
  virtual void DoDeallocate(void*) {
    // This method will be pure virtual once consumer migrate from the deprected
    // version that takes a `Layout` parameter. In the meantime, the check that
    // this method is implemented is deferred to run-time.
    PW_ASSERT(false);
  }
 
  virtual void DoDeallocate(void* ptr, Layout) { DoDeallocate(ptr); }
 
  virtual Result<Layout> DoGetInfo(InfoType, const void*) const {
    return Status::Unimplemented();
  }
 
  const Capabilities capabilities_;
};
 
namespace allocator {
 
// Alias for module consumers using the older name for the above type.
using Deallocator = ::pw::Deallocator;
 
}  // namespace allocator
}  // namespace pw