apps/codecs/libmad/fixed.c

   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  * $Id$
  20  */
  21
  22 # ifdef HAVE_CONFIG_H
  23 #  include "config.h"
  24 # endif
  25
  26 # include "global.h"
  27
  28 # include "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 }