typed_pool.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 <cstddef>
 
#include "pw_allocator/chunk_pool.h"
#include "pw_allocator/hardening.h"
#include "pw_bytes/span.h"
 
namespace pw::allocator {
 
 
template <typename T>
class TypedPool : public ChunkPool {
 public:
  static constexpr size_t SizeNeeded(size_t num_objects);
 
  static constexpr size_t AlignmentNeeded() {
    return std::max(alignof(T), ChunkPool::kMinAlignment);
  }
 
  template <size_t kNumObjects>
  struct Buffer {
    static_assert(kNumObjects != 0);
    alignas(
        AlignmentNeeded()) std::array<std::byte, SizeNeeded(kNumObjects)> data;
  };
 
  template <size_t kNumObjects>
  TypedPool(Buffer<kNumObjects>& buffer)
      : ChunkPool(buffer.data, Layout::Of<T>()) {}
 
  TypedPool(ByteSpan region) : ChunkPool(region, Layout::Of<T>()) {}
 
  template <int&... kExplicitGuard, typename... Args>
  T* New(Args&&... args);
 
  template <int&... kExplicitGuard, typename... Args>
  UniquePtr<T> MakeUnique(Args&&... args) {
    return UniquePtr<T>(New(std::forward<Args>(args)...), *this);
  }
};
 
 
// Template method implementations.
 
template <typename T>
constexpr size_t TypedPool<T>::SizeNeeded(size_t num_objects) {
  size_t needed = std::max(sizeof(T), ChunkPool::kMinSize);
  Hardening::Multiply(needed, num_objects);
  return needed;
}
 
template <typename T>
template <int&... kExplicitGuard, typename... Args>
T* TypedPool<T>::New(Args&&... args) {
  void* ptr = Allocate();
  return ptr != nullptr ? new (ptr) T(std::forward<Args>(args)...) : nullptr;
}
 
}  // namespace pw::allocator