chunks.h

// Copyright 2025 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_multibuf/internal/chunk_iterator.h"
 
namespace pw::multibuf {
 
// Forward declaration for friending.
namespace test {
class IteratorTest;
}  // namespace test
 
namespace internal {
class GenericMultiBuf;
 
template <typename Derived, typename Deque>
class ChunksImpl {
 public:
  using size_type = typename Deque::size_type;
  using value_type = typename Deque::value_type;
  using difference_type = typename Deque::difference_type;
  using iterator = ChunkIterator<size_type, /*kIsConst=*/false>;
  using const_iterator = ChunkIterator<size_type, /*kIsConst=*/true>;
 
  constexpr ChunksImpl() = default;
 
  constexpr size_type size() const { return deque().size() / depth(); }
  constexpr size_type capacity() const { return deque().capacity() / depth(); }
 
  constexpr const_iterator cbegin() const { return derived().begin(); }
  constexpr const_iterator cend() const { return derived().end(); }
 
 protected:
  constexpr void Init(Deque& deque, size_type depth) {
    derived().begin_.deque_ = &deque;
    derived().begin_.depth_ = depth;
    derived().end_.deque_ = &deque;
    derived().end_.depth_ = depth;
    derived().end_.index_ = deque.size();
  }
 
  constexpr Derived& derived() { return static_cast<Derived&>(*this); }
  constexpr const Derived& derived() const {
    return static_cast<const Derived&>(*this);
  }
 
  constexpr const Deque& deque() const { return *(derived().begin_.deque_); }
  constexpr size_type depth() const { return derived().begin_.depth_; }
};
 
}  // namespace internal
 
template <typename Deque>
class Chunks : public internal::ChunksImpl<Chunks<Deque>, Deque> {
 private:
  using Base = internal::ChunksImpl<Chunks<Deque>, Deque>;
 
 public:
  using typename Base::const_iterator;
  using typename Base::difference_type;
  using typename Base::iterator;
  using typename Base::size_type;
  using typename Base::value_type;
 
  constexpr Chunks() = default;
 
  constexpr iterator begin() const { return begin_; }
  constexpr iterator end() const { return end_; }
 
 private:
  template <typename, typename>
  friend class ::pw::multibuf::internal::ChunksImpl;
  friend class ::pw::multibuf::internal::GenericMultiBuf;
 
  // For unit testing.
  friend class ::pw::multibuf::test::IteratorTest;
 
  constexpr Chunks(Deque& deque, size_type depth) { Base::Init(deque, depth); }
 
  iterator begin_;
  iterator end_;
};
 
template <typename Deque>
class ConstChunks
    : public internal::ChunksImpl<ConstChunks<Deque>, const Deque> {
 private:
  using Base = internal::ChunksImpl<ConstChunks<Deque>, const Deque>;
 
 public:
  using typename Base::const_iterator;
  using typename Base::difference_type;
  using typename Base::size_type;
  using typename Base::value_type;
 
  constexpr ConstChunks() = default;
 
  constexpr const_iterator begin() const { return begin_; }
  constexpr const_iterator end() const { return end_; }
 
 private:
  template <typename, typename>
  friend class ::pw::multibuf::internal::ChunksImpl;
  friend class ::pw::multibuf::internal::GenericMultiBuf;
 
  constexpr ConstChunks(const Deque& deque, size_type depth) {
    Base::Init(deque, depth);
  }
 
  const_iterator begin_;
  const_iterator end_;
};
 
}  // namespace pw::multibuf