/* ring_buffer.c
 *
 * Copyright (c) 2002, 2003 Bruce Kroeze
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 * ---------------------------------
 *
 * basic ring buffer for PICs
 *
 * Revisions:
 * 25 Dec 2002 - Initial Version
 */

#ifndef MAX_RING_SIZE
#define MAX_RING_SIZE 16
#endif

#ifndef RING_TYPE
#define RING_TYPE char
#endif

RING_TYPE ring[MAX_RING_SIZE];
int ring_read_ix;
int ring_write_ix;

void ring_clear()
{
  int i;
  for (i=0; i < MAX_RING_SIZE; ++i)
    ring[i] = 0;
  ring_read_ix = 0;
  ring_write_ix = 0;
}

void ring_append(RING_TYPE ch)
{
  ring[ring_write_ix] = ch;
  
  ring_write_ix++;
  if (ring_write_ix == MAX_RING_SIZE)
    ring_write_ix = 0;
}

int ring_offset(ix, offset)
{
  int val;
  val = ix + offset;
  if (val >= MAX_RING_SIZE) {
    val -= MAX_RING_SIZE;
  }
  return val;
}

RING_TYPE ring_peek(int offset)
{
  int ix;
  ix = ring_offset(ring_read_ix, offset);
  return ring[ix];
}

int inc_ring_read_ix() {
  if (ring_read_ix != ring_write_ix) {
    ++ring_read_ix;
    if (ring_read_ix == MAX_RING_SIZE)
      ring_read_ix = 0;
    return 1;
  }
  else {
    return 0;
  }
}

RING_TYPE ring_pop() {
  RING_TYPE ret;

  ret = ring[ring_read_ix];
  ring[ring_read_ix] = 0;
  inc_ring_read_ix();
  return ret;
}

int ring_read(RING_TYPE *buf, int count)
{
  int i, j;

  for (i=0; i < count; ++i) {
    buf[i] = ring[ring_read_ix];
    if (!inc_ring_read_ix())
      break;
  }

  while (i < count) {
    buf[i] = 0;
    ++i;
  }
}

#ifdef RINGTEST

int get_raw_ring(RING_TYPE *buf)
{
  int ix;
  for (ix=0; ix<MAX_RING_SIZE; ++ix)
    {
      buf[ix] = ring[ix];
    }
  return ring_read_ix;
}

#endif