fixed.cpp

00001 /*
00002  * libmad - MPEG audio decoder library
00003  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
00004  *
00005  * This program is free software; you can redistribute it and/or modify
00006  * it under the terms of the GNU General Public License as published by
00007  * the Free Software Foundation; either version 2 of the License, or
00008  * (at your option) any later version.
00009  *
00010  * This program is distributed in the hope that it will be useful,
00011  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00012  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00013  * GNU General Public License for more details.
00014  *
00015  * You should have received a copy of the GNU General Public License
00016  * along with this program; if not, write to the Free Software
00017  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
00018  *
00019  * $Id: fixed.c,v 1.1 2010/11/23 20:12:57 andy Exp $
00020  */
00021 
00022 #  include "config.h"
00023 
00024 # include "global.h"
00025 
00026 # include "fixed.h"
00027 
00028 /*
00029  * NAME:    fixed->abs()
00030  * DESCRIPTION: return absolute value of a fixed-point number
00031  */
00032 mad_fixed_t mad_f_abs(mad_fixed_t x)
00033 {
00034   return x < 0 ? -x : x;
00035 }
00036 
00037 /*
00038  * NAME:    fixed->div()
00039  * DESCRIPTION: perform division using fixed-point math
00040  */
00041 mad_fixed_t mad_f_div(mad_fixed_t x, mad_fixed_t y)
00042 {
00043   mad_fixed_t q, r;
00044   unsigned int bits;
00045 
00046   q = mad_f_abs(x / y);
00047 
00048   if (x < 0) {
00049     x = -x;
00050     y = -y;
00051   }
00052 
00053   r = x % y;
00054 
00055   if (y < 0) {
00056     x = -x;
00057     y = -y;
00058   }
00059 
00060   if (q > mad_f_intpart(MAD_F_MAX) &&
00061       !(q == -mad_f_intpart(MAD_F_MIN) && r == 0 && (x < 0) != (y < 0)))
00062     return 0;
00063 
00064   for (bits = MAD_F_FRACBITS; bits && r; --bits) {
00065     q <<= 1, r <<= 1;
00066     if (r >= y)
00067       r -= y, ++q;
00068   }
00069 
00070   /* round */
00071   if (2 * r >= y)
00072     ++q;
00073 
00074   /* fix sign */
00075   if ((x < 0) != (y < 0))
00076     q = -q;
00077 
00078   return q << bits;
00079 }