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# fixed.c

    00001 /*
    00002  * libmad - MPEG audio decoder library
    00003  * Copyright (C) 2000-2003 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 2003/08/31 18:59:46 gabest Exp $
    00020  */
    00021
    00022 # ifdef HAVE_CONFIG_H
    00023 #  include "config.h"
    00024 # endif
    00025
    00026 # include "global.h"
    00027
    00028 # include "fixed.h"
    00029
    00030 /*
    00031  * NAME:        fixed->abs()
    00032  * DESCRIPTION: return absolute value of a fixed-point number
    00033  */
    00034 mad_fixed_t mad_f_abs(mad_fixed_t x)
    00035 {
    00036   return x < 0 ? -x : x;
    00037 }
    00038
    00039 /*
    00040  * NAME:        fixed->div()
    00041  * DESCRIPTION: perform division using fixed-point math
    00042  */
    00043 mad_fixed_t mad_f_div(mad_fixed_t x, mad_fixed_t y)
    00044 {
    00045   mad_fixed_t q, r;
    00046   unsigned int bits;
    00047
    00048   q = mad_f_abs(x / y);
    00049
    00050   if (x < 0) {
    00051     x = -x;
    00052     y = -y;
    00053   }
    00054
    00055   r = x % y;
    00056
    00057   if (y < 0) {
    00058     x = -x;
    00059     y = -y;
    00060   }
    00061
    00062   if (q > mad_f_intpart(MAD_F_MAX) &&
    00063       !(q == -mad_f_intpart(MAD_F_MIN) && r == 0 && (x < 0) != (y < 0)))
    00064     return 0;
    00065
    00066   for (bits = MAD_F_FRACBITS; bits && r; --bits) {
    00067     q <<= 1, r <<= 1;
    00068     if (r >= y)
    00069       r -= y, ++q;
    00070   }
    00071
    00072   /* round */
    00073   if (2 * r >= y)
    00074     ++q;
    00075
    00076   /* fix sign */
    00077   if ((x < 0) != (y < 0))
    00078     q = -q;
    00079
    00080   return q << bits;
    00081 }