tpl_ring_buffer.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
#ifndef TPL_RING_BUFFER_H
#define TPL_RING_BUFFER_H
 
#include <cstddef>
#include <iterator>
#include <memory>
#include <type_traits>
#include <utility>
 
#include <ah-errors.H>
 
namespace Aleph {
 
template <typename T>
class RingBuffer
{
  static_assert(std::is_move_constructible_v<T>,
                "RingBuffer requires a move-constructible element type");
  static_assert(std::is_move_assignable_v<T>, "RingBuffer requires a move-assignable element type");
 
  T *buf_ = nullptr;
  size_t cap_ = 0;
  size_t head_ = 0;  // physical index of the oldest element
  size_t n_ = 0;
 
  static T *allocate(size_t m)
  {
    return std::allocator<T>().allocate(m);
  }
 
  static void deallocate(T *p, size_t m) noexcept
  {
    std::allocator<T>().deallocate(p, m);
  }
 
  // Physical index of the i-th logical element.
  size_t phys(const size_t i) const noexcept
  {
    return (head_ + i) % cap_;
  }
 
  // Destroys all elements without releasing the storage.
  void destroy_all() noexcept
  {
    for (size_t i = 0; i < n_; ++i)
      std::destroy_at(buf_ + phys(i));
    head_ = 0;
    n_ = 0;
  }
 
public:
  using Item_Type = T;       
  using value_type = T;      
  using size_type = size_t;  
 
  template <bool IsConst>
  class basic_iterator
  {
    using BufPtr = std::conditional_t<IsConst, const RingBuffer *, RingBuffer *>;
 
    BufPtr rb_ = nullptr;
    size_t idx_ = 0;  // logical index
 
    static size_t negative_magnitude(const std::ptrdiff_t i) noexcept
    {
      return static_cast<size_t>(-(i + 1)) + 1;
    }
 
    static size_t add_offset(const size_t idx, const std::ptrdiff_t i) noexcept
    {
      return i < 0 ? idx - negative_magnitude(i) : idx + static_cast<size_t>(i);
    }
 
    static size_t sub_offset(const size_t idx, const std::ptrdiff_t i) noexcept
    {
      return i < 0 ? idx + negative_magnitude(i) : idx - static_cast<size_t>(i);
    }
 
  public:
    using iterator_category = std::random_access_iterator_tag;      
    using value_type = T;                                           
    using difference_type = std::ptrdiff_t;                         
    using reference = std::conditional_t<IsConst, const T &, T &>;  
    using pointer = std::conditional_t<IsConst, const T *, T *>;    
 
    basic_iterator() = default;
 
    basic_iterator(BufPtr rb, const size_t idx) noexcept : rb_(rb), idx_(idx) {}
 
    template <bool B> requires (IsConst and not B)
    basic_iterator(const basic_iterator<B> &it) noexcept : rb_(it.buffer()), idx_(it.index())
    {}
 
    BufPtr buffer() const noexcept
    {
      return rb_;
    }
 
    size_t index() const noexcept
    {
      return idx_;
    }
 
    reference operator * () const noexcept
    {
      return (*rb_)(idx_);
    }
 
    pointer operator ->() const noexcept
    {
      return &(*rb_)(idx_);
    }
 
    reference operator [] (const difference_type i) const noexcept
    {
      return (*rb_)(add_offset(idx_, i));
    }
 
    basic_iterator &operator ++ () noexcept
    {
      ++idx_;
      return *this;
    }
 
    basic_iterator operator ++ (int) noexcept
    {
      basic_iterator ret = *this;
      ++idx_;
      return ret;
    }
 
    basic_iterator &operator -- () noexcept
    {
      --idx_;
      return *this;
    }
 
    basic_iterator operator -- (int) noexcept
    {
      basic_iterator ret = *this;
      --idx_;
      return ret;
    }
 
    basic_iterator &operator += (const difference_type i) noexcept
    {
      idx_ = add_offset(idx_, i);
      return *this;
    }
 
    basic_iterator &operator -= (const difference_type i) noexcept
    {
      idx_ = sub_offset(idx_, i);
      return *this;
    }
 
    basic_iterator operator + (difference_type i) const noexcept
    {
      basic_iterator ret = *this;
      return ret += i;
    }
 
    basic_iterator operator - (difference_type i) const noexcept
    {
      basic_iterator ret = *this;
      return ret -= i;
    }
 
    difference_type operator - (const basic_iterator &it) const noexcept
    {
      return static_cast<difference_type>(idx_) - static_cast<difference_type>(it.index());
    }
 
    bool operator == (const basic_iterator &it) const noexcept
    {
      return rb_ == it.buffer() and idx_ == it.index();
    }
 
    bool operator != (const basic_iterator &it) const noexcept
    {
      return not (*this == it);
    }
 
    bool operator < (const basic_iterator &it) const noexcept
    {
      return idx_ < it.index();
    }
 
    bool operator <= (const basic_iterator &it) const noexcept
    {
      return idx_ <= it.index();
    }
 
    bool operator > (const basic_iterator &it) const noexcept
    {
      return idx_ > it.index();
    }
 
    bool operator >= (const basic_iterator &it) const noexcept
    {
      return idx_ >= it.index();
    }
  };
 
  using iterator = basic_iterator<false>;       
  using const_iterator = basic_iterator<true>;  
 
  explicit RingBuffer(const size_t cap) : cap_(cap)
  {
    ah_invalid_argument_if(cap == 0) << "RingBuffer: capacity must be positive";
    buf_ = allocate(cap_);
  }
 
  RingBuffer(const RingBuffer &rb)
    requires std::is_copy_constructible_v<T>
    : cap_(rb.cap_)
  {
    buf_ = allocate(cap_);
    try
      {
        for (; n_ < rb.n_; ++n_)
          ::new (static_cast<void *>(buf_ + n_)) T(rb(n_));
      }
    catch (...)
      {
        destroy_all();
        deallocate(buf_, cap_);
        throw;
      }
  }
 
  RingBuffer(RingBuffer &&rb) noexcept
  {
    swap(rb);
  }
 
  RingBuffer &operator = (const RingBuffer &rb)
    requires std::is_copy_constructible_v<T>
  {
    if (this == &rb)
      return *this;
    RingBuffer tmp(rb);  // strong guarantee
    swap(tmp);
    return *this;
  }
 
  RingBuffer &operator = (RingBuffer &&rb) noexcept
  {
    swap(rb);
    return *this;
  }
 
  ~RingBuffer()
  {
    if (buf_ != nullptr)
      {
        destroy_all();
        deallocate(buf_, cap_);
      }
  }
 
  void swap(RingBuffer &rb) noexcept
  {
    std::swap(buf_, rb.buf_);
    std::swap(cap_, rb.cap_);
    std::swap(head_, rb.head_);
    std::swap(n_, rb.n_);
  }
 
  // -- capacity -------------------------------------------------------------
 
  [[nodiscard]] size_t size() const noexcept
  {
    return n_;
  }
 
  [[nodiscard]] size_t capacity() const noexcept
  {
    return cap_;
  }
 
  [[nodiscard]] size_t available() const noexcept
  {
    return cap_ - n_;
  }
 
  [[nodiscard]] bool is_empty() const noexcept
  {
    return n_ == 0;
  }
 
  [[nodiscard]] bool is_full() const noexcept
  {
    return n_ == cap_;
  }
 
  void empty() noexcept
  {
    destroy_all();
  }
 
  void clear() noexcept
  {
    destroy_all();
  }
 
  // -- element access -------------------------------------------------------
 
  [[nodiscard]] T &operator [] (const size_t i)
  {
    ah_out_of_range_error_if(i >= n_) << "RingBuffer: index out of range";
    return buf_[phys(i)];
  }
 
  [[nodiscard]] const T &operator [] (const size_t i) const
  {
    ah_out_of_range_error_if(i >= n_) << "RingBuffer: index out of range";
    return buf_[phys(i)];
  }
 
  [[nodiscard]] T &operator () (const size_t i) noexcept
  {
    return buf_[phys(i)];
  }
 
  [[nodiscard]] const T &operator () (const size_t i) const noexcept
  {
    return buf_[phys(i)];
  }
 
  [[nodiscard]] T &get_first()
  {
    ah_underflow_error_if(n_ == 0) << "RingBuffer::get_first(): empty";
    return buf_[head_];
  }
 
  [[nodiscard]] const T &get_first() const
  {
    ah_underflow_error_if(n_ == 0) << "RingBuffer::get_first(): empty";
    return buf_[head_];
  }
 
  [[nodiscard]] T &get_last()
  {
    ah_underflow_error_if(n_ == 0) << "RingBuffer::get_last(): empty";
    return buf_[phys(n_ - 1)];
  }
 
  [[nodiscard]] const T &get_last() const
  {
    ah_underflow_error_if(n_ == 0) << "RingBuffer::get_last(): empty";
    return buf_[phys(n_ - 1)];
  }
 
  [[nodiscard]] T &front()
  {
    return get_first();
  }
 
  [[nodiscard]] const T &front() const
  {
    return get_first();
  }
 
  [[nodiscard]] T &back()
  {
    return get_last();
  }
 
  [[nodiscard]] const T &back() const
  {
    return get_last();
  }
 
  // -- modifiers ------------------------------------------------------------
 
  template <class... Args>
  T &emplace(Args &&...args)
  {
    ah_overflow_error_if(is_full()) << "RingBuffer::emplace(): buffer full";
    T *slot = buf_ + phys(n_);
    ::new (static_cast<void *>(slot)) T(std::forward<Args>(args)...);
    ++n_;
    return *slot;
  }
 
  T &put(const T &item)
    requires std::is_copy_constructible_v<T>
  {
    return emplace(item);
  }
 
  T &put(T &&item)
  {
    return emplace(std::move(item));
  }
 
  T &push(const T &item)
    requires std::is_copy_constructible_v<T>
  {
    return put(item);
  }
 
  T &push(T &&item)
  {
    return put(std::move(item));
  }
 
  bool put_overwrite(const T &item)
    requires(std::is_copy_constructible_v<T> and std::is_copy_assignable_v<T>)
  {
    if (not is_full())
      {
        put(item);
        return false;
      }
    buf_[head_] = item;
    head_ = (head_ + 1) % cap_;
    return true;
  }
 
  bool put_overwrite(T &&item)
    requires std::is_move_assignable_v<T>
  {
    if (not is_full())
      {
        put(std::move(item));
        return false;
      }
    buf_[head_] = std::move(item);
    head_ = (head_ + 1) % cap_;
    return true;
  }
 
  T get()
  {
    ah_underflow_error_if(n_ == 0) << "RingBuffer::get(): empty buffer";
    T *slot = buf_ + head_;
    T ret = std::move(*slot);
    std::destroy_at(slot);
    head_ = (head_ + 1) % cap_;
    --n_;
    return ret;
  }
 
  T pop()
  {
    return get();
  }
 
  // -- iteration ------------------------------------------------------------
 
  iterator begin() noexcept
  {
    return iterator(this, 0);
  }
 
  iterator end() noexcept
  {
    return iterator(this, n_);
  }
 
  const_iterator begin() const noexcept
  {
    return const_iterator(this, 0);
  }
 
  const_iterator end() const noexcept
  {
    return const_iterator(this, n_);
  }
 
  const_iterator cbegin() const noexcept
  {
    return begin();
  }
 
  const_iterator cend() const noexcept
  {
    return end();
  }
 
  template <class Operation>
  bool traverse(Operation operation)
  {
    for (size_t i = 0; i < n_; ++i)
      if (not operation(buf_[phys(i)]))
        return false;
    return true;
  }
 
  template <class Operation>
  bool traverse(Operation operation) const
  {
    for (size_t i = 0; i < n_; ++i)
      if (not operation(buf_[phys(i)]))
        return false;
    return true;
  }
 
  // -- comparison -----------------------------------------------------------
 
  bool operator == (const RingBuffer &rb) const
  {
    if (n_ != rb.n_)
      return false;
    for (size_t i = 0; i < n_; ++i)
      if (not ((*this)(i) == rb(i)))
        return false;
    return true;
  }
 
  bool operator != (const RingBuffer &rb) const
  {
    return not (*this == rb);
  }
};
 
}  // end namespace Aleph
 
#endif  // TPL_RING_BUFFER_H