Games/Doom/m_fixed.c

   1 // Emacs style mode select   -*- C++ -*-
   2 //-----------------------------------------------------------------------------
   3 //
   4 // $Id$
   5 //
   6 // Copyright (C) 1993-1996 by id Software, Inc.
   7 //
   8 // This source is available for distribution and/or modification
   9 // only under the terms of the DOOM Source Code License as
  10 // published by id Software. All rights reserved.
  11 //
  12 // The source is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
  15 // for more details.
  16 //
  17 // $Log$
  18 // Revision 1.2  2002/04/27 09:51:47  hkiel
  19 // reversed order of FixedDiv() and helper function FixedDiv2() to avoid
  20 // implicit prototype
  21 //
  22 // Revision 1.1  2000/02/29 18:21:04  stegerg
  23 // Doom port based on ADoomPPC. Read README.AROS!
  24 //
  25 //
  26 // DESCRIPTION:
  27 //      Fixed point implementation.
  28 //
  29 //-----------------------------------------------------------------------------
  30
  31
  32 static const char
  33 rcsid[] = "$Id$";
  34
  35 #include "stdlib.h"
  36
  37 #include "doomtype.h"
  38 #include "i_system.h"
  39
  40 #ifdef __GNUG__
  41 #pragma implementation "m_fixed.h"
  42 #endif
  43 #include "m_fixed.h"
  44
  45
  46
  47
  48 // Fixme. __USE_C_FIXED__ or something.
  49
  50 fixed_t
  51 FixedMul
  52 ( fixed_t       a,
  53   fixed_t       b )
  54 {
  55     return ((long long) a * (long long) b) >> FRACBITS;
  56 }
  57
  58
  59
  60 //
  61 // FixedDiv, C version.
  62 //
  63
  64 fixed_t
  65 FixedDiv2
  66 ( fixed_t       a,
  67   fixed_t       b )
  68 {
  69 #if 0
  70     long long c;
  71     c = ((long long)a<<16) / ((long long)b);
  72     return (fixed_t) c;
  73 #else
  74
  75     double c;
  76
  77     c = ((double)a) / ((double)b) * FRACUNIT;
  78
  79     if (c >= 2147483648.0 || c < -2147483648.0)
  80         I_Error("FixedDiv: divide by zero");
  81     return (fixed_t) c;
  82 #endif
  83 }
  84
  85
  86
  87 fixed_t
  88 FixedDiv
  89 ( fixed_t       a,
  90   fixed_t       b )
  91 {
  92     if ( (abs(a)>>14) >= abs(b))
  93         return (a^b)<0 ? MININT : MAXINT;
  94     return FixedDiv2 (a,b);
  95 }
  96
  97
  98