1 /* a simple ring buffer 2 Copyright (C) 2006, 2009-2012 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 24 void 25 i_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 36 bool 37 i_ring_empty (I_ring const *ir) 38 { 39 return ir->ir_empty; 40 } 41 42 int 43 i_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 55 int 56 i_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