| /* 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/>. */ |
| |
| /* written by Jim Meyering */ |
| |
| #include <config.h> |
| #include "i-ring.h" |
| |
| #include <stdlib.h> |
| |
| void |
| i_ring_init (I_ring *ir, int default_val) |
| { |
| int i; |
| ir->ir_empty = true; |
| ir->ir_front = 0; |
| ir->ir_back = 0; |
| for (i = 0; i < I_RING_SIZE; i++) |
| ir->ir_data[i] = default_val; |
| ir->ir_default_val = default_val; |
| } |
| |
| bool |
| i_ring_empty (I_ring const *ir) |
| { |
| return ir->ir_empty; |
| } |
| |
| int |
| i_ring_push (I_ring *ir, int val) |
| { |
| unsigned int dest_idx = (ir->ir_front + !ir->ir_empty) % I_RING_SIZE; |
| int old_val = ir->ir_data[dest_idx]; |
| ir->ir_data[dest_idx] = val; |
| ir->ir_front = dest_idx; |
| if (dest_idx == ir->ir_back) |
| ir->ir_back = (ir->ir_back + !ir->ir_empty) % I_RING_SIZE; |
| ir->ir_empty = false; |
| return old_val; |
| } |
| |
| int |
| i_ring_pop (I_ring *ir) |
| { |
| int top_val; |
| if (i_ring_empty (ir)) |
| abort (); |
| top_val = ir->ir_data[ir->ir_front]; |
| ir->ir_data[ir->ir_front] = ir->ir_default_val; |
| if (ir->ir_front == ir->ir_back) |
| ir->ir_empty = true; |
| else |
| ir->ir_front = ((ir->ir_front + I_RING_SIZE - 1) % I_RING_SIZE); |
| return top_val; |
| } |