comm_buffers.h

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/***************************************************************************
 *   Copyright (C) 2024 Alec Leamas                                        *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, see <https://www.gnu.org/licenses/>. *
 **************************************************************************/
 
#ifndef COMM_BUFFERS_H_
#define COMM_BUFFERS_H_
 
#include <deque>
#include <memory>
#include <mutex>
#include <stdexcept>
#include <string>
#include <vector>
 
#ifdef _MSC_VER
typedef unsigned __int8 uint8_t;
#else
#include <cstdint>
#endif
 
class BufferError : public std::logic_error {
public:
  BufferError(const std::string& why) : logic_error(why) {};
};
 
class OutputBuffer {
public:
  void Put(const std::string line);
 
  bool Get(std::string& line);
 
private:
  std::deque<std::string> m_buffer;
  std::mutex m_mutex;
};
 
class LineBuffer {
public:
  void Put(uint8_t ch);
 
  bool HasLine() const;
 
  std::vector<uint8_t> GetLine();
 
  LineBuffer() : m_line_count(0), m_last_ch('\n') {}
 
private:
  std::vector<uint8_t> m_buff;
  int m_line_count;
  uint8_t m_last_ch;
};
 
class N0183Buffer {
public:
  void Put(uint8_t ch);
 
  bool HasSentence() const { return !m_lines.empty(); }
 
  std::string GetSentence();
 
  N0183Buffer() : m_state(State::PrefixWait) {}
 
private:
  std::deque<std::string> m_lines;
  std::vector<uint8_t> m_line;
  enum class State { PrefixWait, Data, CsDigit1, CsDigit2 } m_state;
};
 
template <class T>
class CircularBuffer {
public:
  explicit CircularBuffer(size_t size)
      : m_buf(std::unique_ptr<T[]>(new T[size])),
        m_max_size(size),
        m_head(0),
        m_tail(0),
        m_full(false) {}
 
  void Reset() noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    m_head = 0;
    m_tail = 0;
    m_full = false;
  }
 
  size_t Capacity() const noexcept { return m_max_size; }
 
  size_t Size() const noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    size_t size = m_max_size;
    if (!m_full)
      size = m_head >= m_tail ? m_head - m_tail : m_head + m_max_size - m_tail;
    return size;
  }
 
  bool IsEmpty() const noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    return (!m_full && (m_head == m_tail));
  }
 
  bool IsFull() const noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    return m_full;
  }
 
  bool SafePut(const T& item) noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    if (m_full) return false;
    DoPut(item);
    return true;
  }
 
  void Put(const T& item) {
    std::lock_guard<std::mutex> lock(m_mutex);
    if (m_full) throw BufferError("Put(): full buffer");
    DoPut(item);
  }
 
  T Get() {
    std::lock_guard<std::mutex> lock(m_mutex);
    if (!m_full && m_head == m_tail) throw BufferError("Get(): empty buffer");
    return DoGet();
  }
 
  bool Get(T& item) noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    if (!m_full && m_head == m_tail) return false;
    item = DoGet();
    return true;
  }
 
  const T& Peek() const {
    std::lock_guard<std::mutex> lock(m_mutex);
    if (!m_full && m_head == m_tail) throw BufferError("Peek(): empty buffer");
    return m_buf[m_tail];
  }
 
  bool Peek(T& item) const noexcept {
    std::lock_guard<std::mutex> lock(m_mutex);
    if (!m_full && m_head == m_tail) return false;
    item = m_buf[m_tail];
    return true;
  }
 
private:
  mutable std::mutex m_mutex;
  std::unique_ptr<T[]> m_buf;
  const size_t m_max_size;
  size_t m_head;
  size_t m_tail;
  bool m_full;
 
  void DoPut(const T& item) {
    m_buf[m_head] = item;
    if (m_full) m_tail = (m_tail + 1) % m_max_size;
    m_head = (m_head + 1) % m_max_size;
    m_full = m_head == m_tail;
  }
 
  // Read data and advance the tail (we now have a free space)
  T DoGet() {
    auto val = m_buf[m_tail];
    m_full = false;
    m_tail = (m_tail + 1) % m_max_size;
    return val;
  }
};
 
#endif  // COMM_BUFFERS_H_