m_fixed.c

doom游戏

// Emacs style mode select   -*- C++ -*- 
//-----------------------------------------------------------------------------
//
// $Id:$
//
// Copyright (C) 1993-1996 by id Software, Inc.
//
// This source is available for distribution and/or modification
// only under the terms of the DOOM Source Code License as
// published by id Software. All rights reserved.
//
// The source is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// FITNESS FOR A PARTICULAR PURPOSE. See the DOOM Source Code License
// for more details.
//
// $Log:$
//
// DESCRIPTION:
//	Fixed point implementation.
//
//-----------------------------------------------------------------------------


static const char
rcsid[] = "$Id: m_bbox.c,v 1.1 1997/02/03 22:45:10 b1 Exp $";

#include "stdlib.h"

#include "doomtype.h"
#include "i_system.h"

#ifdef __GNUG__
#pragma implementation "m_fixed.h"
#endif
#include "m_fixed.h"

#include <sdl.h> //!!



// Fixme. __USE_C_FIXED__ or something.



#ifdef __WINS__
#pragma warning(disable:4035)
__inline__
fixed_t
FixedMul
( fixed_t	x,
  fixed_t	y )

{
 __asm
 {
  mov eax,x
  mov edx,y
  imul edx
  add eax, 8000h
  adc edx, 0
  shrd eax, edx, 16
 }
 
}
#pragma warning(default:4035)

 
#else
 
__inline__
fixed_t
FixedMul
( fixed_t	aX,
  fixed_t	aY )
    {
        fixed_t out;
        asm("
        smull r1, r2, %1, %2
        mov r2, r2, lsl #16
        orr %0, r2, r1, lsr #16"
        :"=&r" (out): "r"(aX), "r"(aY): "r1", "r2");
        return out;
    }
#endif 
 


//
// FixedDiv, C version.
//

fixed_t
FixedDiv
( fixed_t	a,
  fixed_t	b )
{
    if ( (abs(a)>>14) >= abs(b))
	return (a^b)<0 ? MININT : MAXINT;
    return FixedDiv2 (a,b);
}



fixed_t
FixedDiv2
( fixed_t	a,
  fixed_t	b )
{
#if 0
    long long c;
    c = ((long long)a<<16) / ((long long)b);
    return (fixed_t) c;
#endif

    double c;

    c = ((double)a) / ((double)b) * FRACUNIT;

    if (c >= 2147483648.0 || c < -2147483648.0)
	I_Error("FixedDiv: divide by zero");
    return (fixed_t) c;
}