dynamic_ptr_vector.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 <type_traits>
#include <utility>
 
#include "pw_allocator/allocator.h"
#include "pw_allocator/unique_ptr.h"
#include "pw_containers/dynamic_vector.h"
 
namespace pw {
 
 
template <typename T, typename SizeType = uint16_t>
class DynamicPtrVector {
 public:
  using value_type = T;
  using size_type = SizeType;
  using difference_type = std::ptrdiff_t;
  using reference = value_type&;
  using const_reference = const value_type&;
  using pointer = value_type*;
  using const_pointer = const value_type*;
  using allocator_type = Allocator;
 
 private:
  // Iterator that automatically dereferences the pointer.
  template <bool kIsConst>
  class Iterator {
   public:
    using iterator_category = std::random_access_iterator_tag;
    using value_type = T;
    using difference_type = std::ptrdiff_t;
    using pointer = std::conditional_t<kIsConst, const T*, T*>;
    using reference = std::conditional_t<kIsConst, const T&, T&>;
 
    constexpr Iterator() = default;
 
    // Allow conversion from non-const to const iterator.
    template <bool kOtherConst,
              typename = std::enable_if_t<kIsConst && !kOtherConst>>
    constexpr Iterator(const Iterator<kOtherConst>& other) : it_(other.it_) {}
 
    reference operator*() const { return **it_; }
    pointer operator->() const { return *it_; }
 
    Iterator& operator++() {
      ++it_;
      return *this;
    }
    Iterator operator++(int) { return Iterator(it_++); }
    Iterator& operator--() {
      --it_;
      return *this;
    }
    Iterator operator--(int) { return Iterator(it_--); }
 
    Iterator& operator+=(difference_type n) {
      it_ += n;
      return *this;
    }
    Iterator& operator-=(difference_type n) {
      it_ -= n;
      return *this;
    }
    friend Iterator operator+(Iterator it, difference_type n) {
      return Iterator(it.it_ + n);
    }
    friend Iterator operator+(difference_type n, Iterator it) {
      return Iterator(it.it_ + n);
    }
    friend Iterator operator-(Iterator it, difference_type n) {
      return Iterator(it.it_ - n);
    }
    friend difference_type operator-(Iterator lhs, Iterator rhs) {
      return lhs.it_ - rhs.it_;
    }
 
    friend bool operator==(Iterator lhs, Iterator rhs) {
      return lhs.it_ == rhs.it_;
    }
    friend bool operator!=(Iterator lhs, Iterator rhs) {
      return lhs.it_ != rhs.it_;
    }
    friend bool operator<(Iterator lhs, Iterator rhs) {
      return lhs.it_ < rhs.it_;
    }
    friend bool operator<=(Iterator lhs, Iterator rhs) {
      return lhs.it_ <= rhs.it_;
    }
    friend bool operator>(Iterator lhs, Iterator rhs) {
      return lhs.it_ > rhs.it_;
    }
    friend bool operator>=(Iterator lhs, Iterator rhs) {
      return lhs.it_ >= rhs.it_;
    }
 
    reference operator[](difference_type n) const { return *(*this + n); }
 
   private:
    using BaseIterator =
        std::conditional_t<kIsConst,
                           typename DynamicVector<T*>::const_iterator,
                           typename DynamicVector<T*>::iterator>;
 
    explicit constexpr Iterator(BaseIterator it) : it_(it) {}
 
    friend class DynamicPtrVector;
    BaseIterator it_;
  };
 
 public:
  using iterator = Iterator<false>;
  using const_iterator = Iterator<true>;
  using reverse_iterator = std::reverse_iterator<iterator>;
  using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
  explicit constexpr DynamicPtrVector(Allocator& allocator)
      : vector_(allocator) {}
 
  ~DynamicPtrVector() { clear(); }
 
  DynamicPtrVector(const DynamicPtrVector&) = delete;
  DynamicPtrVector& operator=(const DynamicPtrVector&) = delete;
 
  DynamicPtrVector(DynamicPtrVector&& other) noexcept = default;
  DynamicPtrVector& operator=(DynamicPtrVector&& other) noexcept {
    clear();
    vector_ = std::move(other.vector_);
    return *this;
  }
 
  // Iterators
 
  iterator begin() { return iterator(vector_.begin()); }
  const_iterator begin() const { return const_iterator(vector_.begin()); }
  const_iterator cbegin() const { return begin(); }
 
  iterator end() { return iterator(vector_.end()); }
  const_iterator end() const { return const_iterator(vector_.end()); }
  const_iterator cend() const { return end(); }
 
  reverse_iterator rbegin() { return reverse_iterator(end()); }
  const_reverse_iterator rbegin() const {
    return const_reverse_iterator(end());
  }
  const_reverse_iterator crbegin() const { return rbegin(); }
 
  reverse_iterator rend() { return reverse_iterator(begin()); }
  const_reverse_iterator rend() const {
    return const_reverse_iterator(begin());
  }
  const_reverse_iterator crend() const { return rend(); }
 
  // Capacity
 
  allocator_type& get_allocator() const { return vector_.get_allocator(); }
  [[nodiscard]] bool empty() const { return vector_.empty(); }
  size_type size() const { return vector_.size(); }
  size_type ptr_capacity() const { return vector_.capacity(); }
  size_type max_size() const { return vector_.max_size(); }
 
  void reserve_ptr(size_type new_capacity) { vector_.reserve(new_capacity); }
 
  void reserve_ptr_exact(size_type new_capacity) {
    vector_.reserve_exact(new_capacity);
  }
 
  [[nodiscard]] bool try_reserve_ptr(size_type new_capacity) {
    return vector_.try_reserve(new_capacity);
  }
  [[nodiscard]] bool try_reserve_ptr_exact(size_type new_capacity) {
    return vector_.try_reserve_exact(new_capacity);
  }
 
  void shrink_to_fit() { vector_.shrink_to_fit(); }
 
  // Element access
 
  reference operator[](size_type pos) { return *vector_[pos]; }
  const_reference operator[](size_type pos) const { return *vector_[pos]; }
 
  reference at(size_type pos) { return *vector_.at(pos); }
  const_reference at(size_type pos) const { return *vector_.at(pos); }
 
  reference front() { return *vector_.front(); }
  const_reference front() const { return *vector_.front(); }
 
  reference back() { return *vector_.back(); }
  const_reference back() const { return *vector_.back(); }
 
  T* const* data() { return vector_.data(); }
  const T* const* data() const { return vector_.data(); }
 
  // Modifiers
 
  void push_back(const T& value) { emplace_back(value); }
 
  void push_back(T&& value) { emplace_back(std::move(value)); }
 
  [[nodiscard]] bool try_push_back(const T& value) {
    return try_emplace_back(value);
  }
 
  [[nodiscard]] bool try_push_back(T&& value) {
    return try_emplace_back(std::move(value));
  }
 
  void pop_back() {
    T* ptr = vector_.back();
    vector_.pop_back();
    Delete(ptr);
  }
 
  [[nodiscard]] pw::UniquePtr<T> take(const_iterator pos) {
    T* ptr = const_cast<T*>(pos.operator->());
    // Remove from vector WITHOUT destroying the object.
    vector_.erase(pos.it_);
    return pw::UniquePtr<T>(ptr, vector_.get_allocator());
  }
 
  template <typename U = T, typename... Args>
  void emplace_back(Args&&... args) {
    PW_ASSERT(try_emplace_back<U>(std::forward<Args>(args)...));
  }
 
  template <typename U = T, typename... Args>
  [[nodiscard]] bool try_emplace_back(Args&&... args) {
    return try_emplace<U>(end(), std::forward<Args>(args)...).has_value();
  }
 
  template <typename U = T, typename... Args>
  iterator emplace(const_iterator pos, Args&&... args) {
    std::optional<iterator> res =
        try_emplace<U>(pos, std::forward<Args>(args)...);
    PW_ASSERT(res.has_value());
    return *res;
  }
 
  template <typename U = T, typename... Args>
  [[nodiscard]] std::optional<iterator> try_emplace(const_iterator pos,
                                                    Args&&... args) {
    static_assert(
        std::is_same_v<T, U> ||
            (std::is_base_of_v<T, U> && (std::is_trivially_destructible_v<U> ||
                                         std::has_virtual_destructor_v<T>)),
        "Objects must inherit from T and be either virtually or trivially "
        "destructible");
    // Get the index since try_reserve() invalidates iterators.
    const auto index = std::distance(vector_.cbegin(), pos.it_);
 
    if (!vector_.try_reserve(vector_.size() + 1)) {
      return std::nullopt;
    }
 
    if (T* ptr = vector_.get_allocator().template New<U>(
            std::forward<Args>(args)...);
        ptr != nullptr) {
      // Skip has_value() check; try_insert() will succeed due to try_reserve().
      return iterator(*vector_.try_insert(vector_.begin() + index, ptr));
    }
    return std::nullopt;
  }
 
  iterator insert(const_iterator pos, const T& value) {
    return emplace(pos, value);
  }
  iterator insert(const_iterator pos, T&& value) {
    return emplace(pos, std::move(value));
  }
 
  [[nodiscard]] std::optional<iterator> try_insert(const_iterator pos,
                                                   const T& value) {
    return try_emplace(pos, value);
  }
  [[nodiscard]] std::optional<iterator> try_insert(const_iterator pos,
                                                   T&& value) {
    return try_emplace(pos, std::move(value));
  }
 
  iterator erase(const_iterator pos) { return erase(pos, pos + 1); }
 
  iterator erase(const_iterator first, const_iterator last) {
    // DynamicVector::erase moves elements to fill the gap, so delete first.
    for (auto it = first; it != last; ++it) {
      Delete(const_cast<T*>(it.operator->()));
    }
    return iterator(vector_.erase(first.it_, last.it_));
  }
 
  void clear() {
    for (T* ptr : vector_) {
      Delete(ptr);
    }
    vector_.clear();
  }
 
 private:
  void Delete(T* ptr) { vector_.get_allocator().Delete(ptr); }
 
  DynamicVector<T*, SizeType> vector_;
};
 
 
}  // namespace pw