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 <memory>
 
#include "pw_allocator/capability.h"
#include "pw_allocator/hardening.h"
#include "pw_allocator/layout.h"
#include "pw_result/result.h"
#include "pw_status/status.h"
#include "pw_status/status_with_size.h"
 
namespace pw {
 
 
class Deallocator {
 public:
  using Capabilities = allocator::Capabilities;
  using Capability = allocator::Capability;
  using Layout = allocator::Layout;
 
  virtual ~Deallocator() = default;
 
  constexpr const Capabilities& capabilities() const { return capabilities_; }
 
  constexpr bool HasCapability(Capability capability) const {
    return capabilities_.has(capability);
  }
 
  inline void Deallocate(void* ptr);
 
  template <typename T,
            int&... kExplicitGuard,
            std::enable_if_t<!std::is_array_v<T>, int> = 0>
  void Delete(T* ptr);
 
  template <typename T,
            int&... kExplicitGuard,
            typename ElementType = std::remove_extent_t<T>,
            std::enable_if_t<is_bounded_array_v<T>, int> = 0>
  void Delete(ElementType* ptr);
 
  template <typename T,
            int&... kExplicitGuard,
            typename ElementType = std::remove_extent_t<T>,
            std::enable_if_t<is_unbounded_array_v<T>, int> = 0>
  void Delete(ElementType* ptr, size_t count);
 
  template <typename ElementType>
  void DeleteArray(ElementType* ptr, size_t count);
 
  inline StatusWithSize GetCapacity() const;
 
  bool IsEqual(const Deallocator& other) const { return this == &other; }
 
 protected:
  // There are downstream consumers that have implemented Allocators outside the
  // `pw` namespace, and that use unqualified names for `is_[un]bounded_array`.
  template <typename T>
  static constexpr bool is_bounded_array_v = ::pw::is_bounded_array_v<T>;
 
  template <typename T>
  static constexpr bool is_unbounded_array_v = ::pw::is_unbounded_array_v<T>;
 
  constexpr Deallocator() = default;
 
  explicit constexpr Deallocator(const Capabilities& capabilities)
      : capabilities_(capabilities) {}
 
  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);
  }
 
  virtual void DoDeallocate([[maybe_unused]] void* ptr) = 0;
 
  virtual Result<Layout> DoGetInfo(InfoType, const void*) const {
    return Status::Unimplemented();
  }
 
 private:
  const Capabilities capabilities_;
};
 
 
// Template and inline method implementations.
 
void Deallocator::Deallocate(void* ptr) {
  if (ptr != nullptr) {
    DoDeallocate(ptr);
  }
}
 
template <typename T,
          int&... kExplicitGuard,
          std::enable_if_t<!std::is_array_v<T>, int>>
void Deallocator::Delete(T* ptr) {
  if constexpr (allocator::Hardening::kIncludesDebugChecks) {
    if (auto result = GetRequestedLayout(ptr); result.ok()) {
      if constexpr (std::has_virtual_destructor_v<T>) {
        PW_ASSERT(result->size() >= sizeof(T) &&
                  result->alignment() >= alignof(T));
      } else {
        PW_ASSERT(*result == Layout::Of<T>());
      }
    }
  }
  DeleteArray<T>(ptr, 1);
}
 
template <typename T,
          int&... kExplicitGuard,
          typename ElementType,
          std::enable_if_t<is_bounded_array_v<T>, int>>
void Deallocator::Delete(ElementType* ptr) {
  size_t count = std::extent_v<T>;
  if (count != 0) {
    DeleteArray<ElementType>(&ptr[0], count);
  }
}
 
template <typename T,
          int&... kExplicitGuard,
          typename ElementType,
          std::enable_if_t<is_unbounded_array_v<T>, int>>
void Deallocator::Delete(ElementType* ptr, size_t count) {
  DeleteArray<ElementType>(ptr, count);
}
 
template <typename ElementType>
void Deallocator::DeleteArray(ElementType* ptr, size_t count) {
  if (!capabilities_.has(Capability::kSkipsDestroy)) {
    std::destroy_n(ptr, count);
  }
  Deallocate(ptr);
}
 
StatusWithSize Deallocator::GetCapacity() const {
  auto result = DoGetInfo(InfoType::kCapacity, nullptr);
  return StatusWithSize(result.status(), Layout::Unwrap(result).size());
}
 
}  // namespace pw