apps/plugins/doom/m_fixed.h

   1 // Emacs style mode select   -*- C++ -*-
   2 //-----------------------------------------------------------------------------
   3 //
   4 // $Id$
   5 //
   6 // Copyright (C) 1993-1996 by id Software, Inc.
   7 //
   8 // This program is free software; you can redistribute it and/or
   9 // modify it under the terms of the GNU General Public License
  10 // as published by the Free Software Foundation; either version 2
  11 // of the License, or (at your option) any later version.
  12 //
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17 //
  18 // DESCRIPTION:
  19 // Fixed point arithemtics, implementation.
  20 //
  21 //-----------------------------------------------------------------------------
  22
  23
  24 #ifndef __M_FIXED__
  25 #define __M_FIXED__
  26
  27
  28 #ifdef __GNUG__
  29 #pragma interface
  30 #endif
  31
  32 #include "doomtype.h"
  33 #include "rockmacros.h"
  34
  35 //
  36 // Fixed point, 32bit as 16.16.
  37 //
  38 #define FRACBITS  16
  39 #define FRACUNIT  (1<<FRACBITS)
  40
  41 #define D_abs(x) ({fixed_t _t = (x), _s = _t >> (8*sizeof _t-1); (_t^_s)-_s;})
  42
  43 typedef int fixed_t;
  44
  45 inline static int FixedMul( int a, int b )
  46 {
  47 #if defined(CPU_COLDFIRE)
  48    // Code contributed by Thom Johansen
  49    register int result;
  50    asm (
  51       "mac.l   %[x],%[y],%%acc0  \n"   /* multiply */
  52       "move.l  %[y],%%d2         \n"
  53       "mulu.l  %[x],%%d2         \n"   /* get lower half, avoid emac stall */
  54       "movclr.l %%acc0,%[result] \n"   /* get higher half */
  55       "asl.l   #8,%[result]      \n"   /* hi <<= 15, plus one free */
  56       "asl.l   #7,%[result]      \n"   /* hi <<= 15, plus one free */
  57       "lsr.l   #8,%%d2           \n"   /* (unsigned)lo >>= 16 */
  58       "lsr.l   #8,%%d2           \n"   /* (unsigned)lo >>= 16 */
  59       "or.l    %%d2 ,%[result]   \n"   /* combine result */
  60    : /* outputs */
  61       [result]"=&d"(result)
  62    : /* inputs */
  63       [x] "d" (a),
  64       [y] "d" (b)
  65    : /* clobbers */
  66       "d2"
  67    );
  68    return result;
  69 #else
  70    return (fixed_t)((long long) a*b >> FRACBITS);
  71 #endif
  72 }
  73
  74 inline static fixed_t FixedDiv( fixed_t  a, fixed_t  b )
  75 {
  76    return (D_abs(a)>>14) >= D_abs(b) ? ((a^b)>>31) ^ MAXINT :
  77           (fixed_t)(((long long) a << FRACBITS) / b);
  78 }
  79
  80 /* CPhipps -
  81  * FixedMod - returns a % b, guaranteeing 0<=a<b
  82  * (notice that the C standard for % does not guarantee this)
  83  */
  84
  85 inline static fixed_t FixedMod(fixed_t a, fixed_t b)
  86 {
  87    if (b & (b-1)) {
  88       fixed_t r = a % b;
  89       return ((r<0) ? r+b : r);
  90    } else
  91       return (a & (b-1));
  92 }
  93
  94 #endif