Adafruit_Keypad_Ringbuffer.h

/*
  Copyright (c) 2014 Arduino.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library 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 Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#ifdef __cplusplus

#ifndef _ADAFRUIT_KEYPAD_RING_BUFFER_
#define _ADAFRUIT_KEYPAD_RING_BUFFER_

#include <stdint.h>
#include <string.h>

// Define constants and variables for buffering incoming serial data.  We're
// using a ring buffer (I think), in which head is the index of the location
// to which to write the next incoming character and tail is the index of the
// location from which to read.

#ifndef SERIAL_BUFFER_SIZE
#define SERIAL_BUFFER_SIZE 256
#endif

template <int N> class Adafruit_Keypad_RingbufferN {
public:
  uint8_t _aucBuffer[N];
  volatile int _iHead;
  volatile int _iTail;

public:
  Adafruit_Keypad_RingbufferN(void);
  void store_char(uint8_t c);
  void clear();
  int read_char();
  int available();
  int availableForStore();
  int peek();
  bool isFull();

private:
  int nextIndex(int index);
};

typedef Adafruit_Keypad_RingbufferN<SERIAL_BUFFER_SIZE>
    Adafruit_Keypad_Ringbuffer;

template <int N>
Adafruit_Keypad_RingbufferN<N>::Adafruit_Keypad_RingbufferN(void) {
  memset(_aucBuffer, 0, N);
  clear();
}

template <int N> void Adafruit_Keypad_RingbufferN<N>::store_char(uint8_t c) {
  int i = nextIndex(_iHead);

  // if we should be storing the received character into the location
  // just before the tail (meaning that the head would advance to the
  // current location of the tail), we're about to overflow the buffer
  // and so we don't write the character or advance the head.
  if (i != _iTail) {
    _aucBuffer[_iHead] = c;
    _iHead = i;
  }
}

template <int N> void Adafruit_Keypad_RingbufferN<N>::clear() {
  _iHead = 0;
  _iTail = 0;
}

template <int N> int Adafruit_Keypad_RingbufferN<N>::read_char() {
  if (_iTail == _iHead)
    return -1;

  uint8_t value = _aucBuffer[_iTail];
  _iTail = nextIndex(_iTail);

  return value;
}

template <int N> int Adafruit_Keypad_RingbufferN<N>::available() {
  int delta = _iHead - _iTail;

  if (delta < 0)
    return N + delta;
  else
    return delta;
}

template <int N> int Adafruit_Keypad_RingbufferN<N>::availableForStore() {
  if (_iHead >= _iTail)
    return N - 1 - _iHead + _iTail;
  else
    return _iTail - _iHead - 1;
}

template <int N> int Adafruit_Keypad_RingbufferN<N>::peek() {
  if (_iTail == _iHead)
    return -1;

  return _aucBuffer[_iTail];
}

template <int N> int Adafruit_Keypad_RingbufferN<N>::nextIndex(int index) {
  return (uint32_t)(index + 1) % N;
}

template <int N> bool Adafruit_Keypad_RingbufferN<N>::isFull() {
  return (nextIndex(_iHead) == _iTail);
}

#endif /* _ADAFRUIT_KEYPAD_RING_BUFFER_ */

#endif /* __cplusplus */