1/* a simple ring buffer
2   Copyright (C) 2006, 2009-2010 Free Software Foundation, Inc.
3
4   This program is free software: you can redistribute it and/or modify
5   it under the terms of the GNU General Public License as published by
6   the Free Software Foundation; either version 3 of the License, or
7   (at your option) any later version.
8
9   This program is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   GNU General Public License for more details.
13
14   You should have received a copy of the GNU General Public License
15   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
16
17/* written by Jim Meyering */
18
19#include <config.h>
20#include "i-ring.h"
21
22#include <stdlib.h>
23
24void
25i_ring_init (I_ring *ir, int default_val)
26{
27  int i;
28  ir->ir_empty = true;
29  ir->ir_front = 0;
30  ir->ir_back = 0;
31  for (i = 0; i < I_RING_SIZE; i++)
32    ir->ir_data[i] = default_val;
33  ir->ir_default_val = default_val;
34}
35
36bool
37i_ring_empty (I_ring const *ir)
38{
39  return ir->ir_empty;
40}
41
42int
43i_ring_push (I_ring *ir, int val)
44{
45  unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
46  int old_val = ir->ir_data[dest_idx];
47  ir->ir_data[dest_idx] = val;
48  ir->ir_front = dest_idx;
49  if (dest_idx == ir->ir_back)
50    ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
51  ir->ir_empty = false;
52  return old_val;
53}
54
55int
56i_ring_pop (I_ring *ir)
57{
58  int top_val;
59  if (i_ring_empty (ir))
60    abort ();
61  top_val = ir->ir_data[ir->ir_front];
62  ir->ir_data[ir->ir_front] = ir->ir_default_val;
63  if (ir->ir_front == ir->ir_back)
64    ir->ir_empty = true;
65  else
66    ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);
67  return top_val;
68}
69