libmad/fixed.c

   1 /*
   2  * libmad - MPEG audio decoder library
   3  * Copyright (C) 2000-2003 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  */
  20
  21 # ifdef HAVE_CONFIG_H
  22 #  include "config.h"
  23 # endif
  24
  25 # include "global.h"
  26
  27 # include "fixed.h"
  28
  29 /*
  30  * NAME:        fixed->abs()
  31  * DESCRIPTION: return absolute value of a fixed-point number
  32  */
  33 mad_fixed_t mad_f_abs(mad_fixed_t x)
  34 {
  35   return x < 0 ? -x : x;
  36 }
  37
  38 /*
  39  * NAME:        fixed->div()
  40  * DESCRIPTION: perform division using fixed-point math
  41  */
  42 mad_fixed_t mad_f_div(mad_fixed_t x, mad_fixed_t y)
  43 {
  44   mad_fixed_t q, r;
  45   u32 bits;
  46
  47   q = mad_f_abs(x / y);
  48
  49   if (x < 0) {
  50     x = -x;
  51     y = -y;
  52   }
  53
  54   r = x % y;
  55
  56   if (y < 0) {
  57     x = -x;
  58     y = -y;
  59   }
  60
  61   if (q > mad_f_intpart(MAD_F_MAX) &&
  62       !(q == -mad_f_intpart(MAD_F_MIN) && r == 0 && (x < 0) != (y < 0)))
  63     return 0;
  64
  65   for (bits = MAD_F_FRACBITS; bits && r; --bits) {
  66     q <<= 1, r <<= 1;
  67     if (r >= y)
  68       r -= y, ++q;
  69   }
  70
  71   /* round */
  72   if (2 * r >= y)
  73     ++q;
  74
  75   /* fix sign */
  76   if ((x < 0) != (y < 0))
  77     q = -q;
  78
  79   return q << bits;
  80 }