ringBuffer.h

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/*
 Copyright (c) 2026 - SD-Innovation S.A.S. - FRANCE
*/
 
/*
ver: 2.x.x - build: 2026-04-28
*/
 
/*
The zlib License

Copyright (c) 2026 SD-Innovation S.A.S. 

This software is provided ‘as-is’, without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.

2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.

3. This notice may not be removed or altered from any source
distribution.

*/
 
#pragma once
 
#include <array>
#include <cstddef>
#include <optional>
 
namespace sdi_toolBox::common::utils
{
//--------------------------------------------------------------
template<class T, std::size_t CAPACITY>
class RingBuffer
{
  static_assert(CAPACITY > 0, "CAPACITY must be > 0");
 
  public:
 
  bool push(const T &value);
 
 
  std::optional<T> pop();
  bool pop(T &value);
 
  [[nodiscard]] std::optional<T> front() const;
 
  [[nodiscard]] bool front(T &value) const;
 
  [[nodiscard]] std::optional<T> back() const;
 
  [[nodiscard]] bool back(T &value) const;
 
 
  [[nodiscard]] bool empty() const;
 
  [[nodiscard]] bool full() const;
 
  [[nodiscard]] std::size_t size() const;
 
  [[nodiscard]] constexpr std::size_t capacity() const;
 
 
  void clear();
 
 
  private:
 
  [[nodiscard]] std::size_t next(std::size_t index) const;
 
 
  std::array<T, CAPACITY> m_data{};            
  std::size_t             m_head{ 0 };         
  std::size_t             m_tail{ 0 };         
  bool                    m_full{ false };     
 
};
//--------------------------------------------------------------
 
//--------------------------------------------------------------
/* Append a value to the buffer. If the buffer is full, the
 * oldest value will be overwritten. Return true if the value
 * was added without overwriting, false if an overwrite occurred. */
template<class T, std::size_t CAPACITY>
bool RingBuffer<T, CAPACITY>::push(const T &value)
{
  m_data[m_head] = value;
  m_head         = next(m_head);
 
  if (m_full)
  {
    m_tail = m_head;     // overwrite the oldest value
    return false;        // indicate that an overwrite occurred
  }
  else
  {
    m_full = (m_head == m_tail);
    return true;     // indicate that the value was added without overwriting
  }
}
//--------------------------------------------------------------
/* Remove and return the oldest value from the buffer. If the
 * buffer is empty, return std::nullopt */
template<class T, std::size_t CAPACITY>
std::optional<T> RingBuffer<T, CAPACITY>::pop()
{
  if (empty())
    return std::nullopt;
  const std::optional<T> result = m_data[m_tail];
  m_tail                        = next(m_tail);
  m_full                        = false;
  return result;
}
//--------------------------------------------------------------
/* Remove the oldest value from the buffer and store it in
 * 'value'. Return true if successful, false if the buffer is empty */
template<class T, std::size_t CAPACITY>
bool RingBuffer<T, CAPACITY>::pop(T &value)
{
  if (empty())
    return false;
 
  value  = m_data[m_tail];
  m_tail = next(m_tail);
  m_full = false;
  return true;
}
//--------------------------------------------------------------
/* Return the oldest value without removing it. If the buffer is
 * empty, return std::nullopt */
template<class T, std::size_t CAPACITY>
std::optional<T> RingBuffer<T, CAPACITY>::front() const
{
  if (empty())
    return std::nullopt;
  return m_data[m_tail];
}
//--------------------------------------------------------------
/* Return the oldest value without removing it and store it in
 * 'value'. Return true if successful, false if the buffer is empty */
template<class T, std::size_t CAPACITY>
bool RingBuffer<T, CAPACITY>::front(T &value) const
{
  if (empty())
    return false;
  value = m_data[m_tail];
  return true;
}
//--------------------------------------------------------------
/* Return the newest value without removing it. If the buffer is
 * empty, return std::nullopt */
template<class T, std::size_t CAPACITY>
std::optional<T> RingBuffer<T, CAPACITY>::back() const
{
  if (empty())
    return std::nullopt;
  return m_data[(m_head == 0) ? CAPACITY - 1 : m_head - 1];
}
//--------------------------------------------------------------
/* Return the newest value without removing it and store it in
 * 'value'. Return true if successful, false if the buffer is empty */
template<class T, std::size_t CAPACITY>
bool RingBuffer<T, CAPACITY>::back(T &value) const
{
  if (empty())
    return false;
  std::size_t backIndex = (m_head == 0) ? CAPACITY - 1 : m_head - 1;
  value                 = m_data[backIndex];
  return true;
}
//--------------------------------------------------------------
/* Check if the buffer is empty */
template<class T, std::size_t CAPACITY>
bool RingBuffer<T, CAPACITY>::empty() const
{
  return !m_full && (m_head == m_tail);
}
//--------------------------------------------------------------
/* Check if the buffer is full */
template<class T, std::size_t CAPACITY>
bool RingBuffer<T, CAPACITY>::full() const
{
  return m_full;
}
//--------------------------------------------------------------
/* Get the number of elements currently in the buffer */
template<class T, std::size_t CAPACITY>
std::size_t RingBuffer<T, CAPACITY>::size() const
{
  if (m_full)
    return CAPACITY;
  if (m_head >= m_tail)
    return m_head - m_tail;
  return CAPACITY - (m_tail - m_head);
}
//--------------------------------------------------------------
/* Get the maximum capacity of the buffer */
template<class T, std::size_t CAPACITY>
[[nodiscard]] constexpr std::size_t RingBuffer<T, CAPACITY>::capacity() const
{
  return CAPACITY;
}
//--------------------------------------------------------------
/* Clear the buffer, resetting it to an empty state */
template<class T, std::size_t CAPACITY>
void RingBuffer<T, CAPACITY>::clear()
{
  m_head = 0;
  m_tail = 0;
  m_full = false;
}
//--------------------------------------------------------------
/* Helper function to calculate the next index in a circular manner */
template<class T, std::size_t CAPACITY>
std::size_t RingBuffer<T, CAPACITY>::next(const std::size_t index) const
{
  // Calculate the next index in a circular manner without using
  // modulus operator for better performance
  const auto nextIndex = index + 1;
  if (nextIndex == CAPACITY)
    return 0;
 
  return nextIndex;
}
//--------------------------------------------------------------
}     // namespace sdi_toolBox::common::utils