| /* definitions for a simple ring buffer |
| Copyright (C) 2006, 2009-2020 Free Software Foundation, Inc. |
| |
| 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 3 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, see <https://www.gnu.org/licenses/>. */ |
| |
| #include <stdbool.h> |
| #include "verify.h" |
| |
| enum { I_RING_SIZE = 4 }; |
| verify (1 <= I_RING_SIZE); |
| |
| /* When ir_empty is true, the ring is empty. |
| Otherwise, ir_data[B..F] are defined, where B..F is the contiguous |
| range of indices, modulo I_RING_SIZE, from back to front, inclusive. |
| Undefined elements of ir_data are always set to ir_default_val. |
| Popping from an empty ring aborts. |
| Pushing onto a full ring returns the displaced value. |
| An empty ring has F==B and ir_empty == true. |
| A ring with one entry still has F==B, but now ir_empty == false. */ |
| struct I_ring |
| { |
| int ir_data[I_RING_SIZE]; |
| int ir_default_val; |
| unsigned int ir_front; |
| unsigned int ir_back; |
| bool ir_empty; |
| }; |
| typedef struct I_ring I_ring; |
| |
| void i_ring_init (I_ring *ir, int ir_default_val); |
| int i_ring_push (I_ring *ir, int val); |
| int i_ring_pop (I_ring *ir); |
| bool i_ring_empty (I_ring const *ir) _GL_ATTRIBUTE_PURE; |