bucket.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 <limits>
 
#include "pw_function/function.h"
#include "pw_span/span.h"
 
namespace pw::allocator::internal {
 
class Bucket final {
 public:
  struct Chunk {
   private:
    friend class Bucket;
 
    static Chunk* FromBytes(std::byte* ptr) {
      return std::launder(reinterpret_cast<Chunk*>(ptr));
    }
 
    const std::byte* AsBytes() const {
      return std::launder(reinterpret_cast<const std::byte*>(this));
    }
 
    std::byte* AsBytes() {
      return std::launder(reinterpret_cast<std::byte*>(this));
    }
 
    Chunk* prev;
    Chunk* next;
  };
 
  Bucket();
 
  explicit Bucket(size_t chunk_size);
 
  Bucket(const Bucket& other) = delete;
  Bucket& operator=(const Bucket& other) = delete;
 
  Bucket(Bucket&& other) { *this = std::move(other); }
  Bucket& operator=(Bucket&& other);
 
  ~Bucket() = default;
 
  void Init(size_t chunk_size = std::numeric_limits<size_t>::max());
 
  static void Init(span<Bucket> buckets, size_t min_chunk_size);
 
  size_t chunk_size() const { return chunk_size_; }
 
  bool empty() const { return sentinel_.next == &sentinel_; }
 
  size_t count() const;
 
  void Add(std::byte* ptr);
 
  void Visit(const Function<void(const std::byte*)>& visitor) const;
 
  std::byte* Remove();
 
  std::byte* RemoveIf(const Function<bool(const std::byte*)>& cond);
 
  static std::byte* Remove(std::byte* ptr);
 
 private:
  static std::byte* Remove(Chunk* chunk);
 
  Chunk sentinel_;
 
  size_t chunk_size_;
};
 
}  // namespace pw::allocator::internal