src/m_fixed.c

   1 // Emacs style mode select   -*- C++ -*-
   2 //-----------------------------------------------------------------------------
   3 //
   4 // Copyright(C) 1993-1996 Id Software, Inc.
   5 // Copyright(C) 2005 Simon Howard
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License
   9 // as published by the Free Software Foundation; either version 2
  10 // of the License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  20 // 02111-1307, USA.
  21 //
  22 // DESCRIPTION:
  23 //      Fixed point implementation.
  24 //
  25 //-----------------------------------------------------------------------------
  26
  27
  28
  29 #include "stdlib.h"
  30
  31 #include "doomtype.h"
  32 #include "i_system.h"
  33
  34 #include "m_fixed.h"
  35
  36
  37
  38
  39 // Fixme. __USE_C_FIXED__ or something.
  40
  41 fixed_t
  42 FixedMul
  43 ( fixed_t       a,
  44   fixed_t       b )
  45 {
  46     return ((int64_t) a * (int64_t) b) >> FRACBITS;
  47 }
  48
  49
  50
  51 //
  52 // FixedDiv, C version.
  53 //
  54
  55 fixed_t FixedDiv(fixed_t a, fixed_t b)
  56 {
  57     if ((abs(a) >> 14) >= abs(b))
  58     {
  59         return (a^b) < 0 ? INT_MIN : INT_MAX;
  60     }
  61     else
  62     {
  63         int64_t result;
  64
  65         result = ((int64_t) a << 16) / b;
  66
  67         return (fixed_t) result;
  68     }
  69 }
  70