1 /* 2 * libmad - MPEG audio decoder library 3 * Copyright (C) 2000-2004 Underbit Technologies, Inc. 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 * 10 * This program is distributed in the hope that it will be useful, 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 * GNU General Public License for more details. 14 * 15 * You should have received a copy of the GNU General Public License 16 * along with this program; if not, write to the Free Software 17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 18 * 19 * $Id: fixed.c,v 1.13 2004/01/23 09:41:32 rob Exp $ 20 */ 21 22 /*# ifdef HAVE_CONFIG_H*/ 23 # include "mad_config.h" 24 /*# endif*/ 25 26 # include "mad_global.h" 27 28 # include "mad_fixed.h" 29 30 /* 31 * NAME: fixed->abs() 32 * DESCRIPTION: return absolute value of a fixed-point number 33 */ 34 mad_fixed_t mad_f_abs(mad_fixed_t x) 35 { 36 return x < 0 ? -x : x; 37 } 38 39 /* 40 * NAME: fixed->div() 41 * DESCRIPTION: perform division using fixed-point math 42 */ 43 mad_fixed_t mad_f_div(mad_fixed_t x, mad_fixed_t y) 44 { 45 mad_fixed_t q, r; 46 unsigned int bits; 47 48 q = mad_f_abs(x / y); 49 50 if (x < 0) { 51 x = -x; 52 y = -y; 53 } 54 55 r = x % y; 56 57 if (y < 0) { 58 x = -x; 59 y = -y; 60 } 61 62 if (q > mad_f_intpart(MAD_F_MAX) && 63 !(q == -mad_f_intpart(MAD_F_MIN) && r == 0 && (x < 0) != (y < 0))) 64 return 0; 65 66 for (bits = MAD_F_FRACBITS; bits && r; --bits) { 67 q <<= 1, r <<= 1; 68 if (r >= y) 69 r -= y, ++q; 70 } 71 72 /* round */ 73 if (2 * r >= y) 74 ++q; 75 76 /* fix sign */ 77 if ((x < 0) != (y < 0)) 78 q = -q; 79 80 return q << bits; 81 } 82