1 /* a simple ring buffer
2 Copyright (C) 2006 Free Software Foundation, Inc.
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 2, or (at your option)
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.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software Foundation,
16 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
18 /* written by Jim Meyering */
26 i_ring_init (I_ring *ir, int default_val)
32 for (i = 0; i < I_RING_SIZE; i++)
33 ir->ir_data[i] = default_val;
34 ir->ir_default_val = default_val;
38 i_ring_empty (I_ring const *ir)
44 i_ring_push (I_ring *ir, int val)
46 unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
47 int old_val = ir->ir_data[dest_idx];
48 ir->ir_data[dest_idx] = val;
49 ir->ir_front = dest_idx;
50 if (dest_idx == ir->ir_back)
51 ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
57 i_ring_pop (I_ring *ir)
60 if (i_ring_empty (ir))
62 top_val = ir->ir_data[ir->ir_front];
63 ir->ir_data[ir->ir_front] = ir->ir_default_val;
64 if (ir->ir_front == ir->ir_back)
67 ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);