bump_allocator.h

// Copyright 2023 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 <cstddef>
 
#include "pw_allocator/abstract_allocator.h"
#include "pw_allocator/capability.h"
#include "pw_bytes/span.h"
 
namespace pw::allocator {
namespace internal {
 
class GenericOwned {
 public:
  virtual ~GenericOwned() = default;
  void set_next(GenericOwned* next) { next_ = next; }
  void Destroy() { DoDestroy(); }
 
 private:
  virtual void DoDestroy() = 0;
 
  GenericOwned* next_ = nullptr;
};
 
template <typename T>
class Owned : public GenericOwned {
 public:
  void set_object(T* object) { object_ = object; }
 
 private:
  void DoDestroy() override;
 
  T* object_ = nullptr;
};
 
}  // namespace internal
 
 
class BumpAllocator : public AbstractAllocator {
 public:
  static constexpr Capabilities kCapabilities = kSkipsDestroy;
 
  constexpr BumpAllocator() : AbstractAllocator(kCapabilities) {}
 
  explicit BumpAllocator(ByteSpan region) : BumpAllocator() { Init(region); }
 
  ~BumpAllocator() override { Reset(); }
 
  void Init(ByteSpan region);
 
  template <typename T, int&... kExplicitGuard, typename... Args>
  T* NewOwned(Args&&... args);
 
  template <typename T, int&... kExplicitGuard, typename... Args>
  [[nodiscard]] UniquePtr<T> MakeUniqueOwned(Args&&... args);
 
 protected:
  void* DoAllocate(Layout layout) override;
 
  void DoDeallocate(void*) override;
 
  size_t DoGetAllocated() const override { return allocated_; }
 
 private:
  void Reset();
 
  size_t allocated_ = 0;
  ByteSpan remaining_;
  internal::GenericOwned* owned_ = nullptr;
};
 
 
// Template method implementations.
 
namespace internal {
 
template <typename T>
void Owned<T>::DoDestroy() {
  if (object_ != nullptr) {
    std::destroy_at(object_);
    object_ = nullptr;
  }
}
 
}  // namespace internal
 
template <typename T, int&... kExplicitGuard, typename... Args>
T* BumpAllocator::NewOwned(Args&&... args) {
  internal::Owned<T>* owned = New<internal::Owned<T>>();
  T* ptr = owned != nullptr ? New<T>(std::forward<Args>(args)...) : nullptr;
  if (ptr != nullptr) {
    owned->set_object(ptr);
    owned->set_next(owned_);
    owned_ = owned;
  }
  return ptr;
}
 
template <typename T, int&... kExplicitGuard, typename... Args>
UniquePtr<T> BumpAllocator::MakeUniqueOwned(Args&&... args) {
  return UniquePtr<T>(NewOwned<T>(std::forward<Args>(args)...), *this);
}
 
}  // namespace pw::allocator