1 /* a simple ring buffer
2 Copyright (C) 2006, 2009-2011 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 3 of the License, or
7 (at your option) any later version.
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, see <http://www.gnu.org/licenses/>. */
17 /* written by Jim Meyering */
24 /* The attribute __pure__ was added in gcc 2.96. */
25 #undef _GL_ATTRIBUTE_PURE
26 #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
27 # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
29 # define _GL_ATTRIBUTE_PURE /* empty */
33 i_ring_init (I_ring *ir, int default_val)
39 for (i = 0; i < I_RING_SIZE; i++)
40 ir->ir_data[i] = default_val;
41 ir->ir_default_val = default_val;
44 bool _GL_ATTRIBUTE_PURE
45 i_ring_empty (I_ring const *ir)
51 i_ring_push (I_ring *ir, int val)
53 unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE;
54 int old_val = ir->ir_data[dest_idx];
55 ir->ir_data[dest_idx] = val;
56 ir->ir_front = dest_idx;
57 if (dest_idx == ir->ir_back)
58 ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE;
64 i_ring_pop (I_ring *ir)
67 if (i_ring_empty (ir))
69 top_val = ir->ir_data[ir->ir_front];
70 ir->ir_data[ir->ir_front] = ir->ir_default_val;
71 if (ir->ir_front == ir->ir_back)
74 ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE);