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m_fixed.c
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m_fixed.c
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// Emacs style mode select -*- C++ -*-
//-----------------------------------------------------------------------------
//
// Copyright(C) 1993-1996 Id Software, Inc.
// Copyright(C) 2005 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
// 02111-1307, USA.
//
// DESCRIPTION:
// Fixed point implementation.
//
//-----------------------------------------------------------------------------
#include "doomtype.h"
#include "i_system.h"
#include "doomdef.h"
#include "m_fixed.h"
static uint32_t quickdiv(uint32_t a, uint32_t div)
{
if (div >= 0x10000) {
div >>= 8;
return ((a / div) << 8)
+ ((a % div) << 8) / div;
} else {
return ((a / div) << 16)
+ ((a % div) << 16) / div;
}
}
#define QUICK_MATH
fixed_t FixedDiv(fixed_t a, fixed_t b)
{
int neg = 0;
if ((abs(a) >> 14) >= abs(b)) {
return (a ^ b) < 0 ? INT_MIN : INT_MAX;
}
#ifdef QUICK_MATH
if (a < 0) {
neg = !neg;
a = -a;
}
if (b < 0) {
neg = !neg;
b = -b;
}
if (!neg)
return quickdiv(a, b);
else
return -(fixed_t)quickdiv(a, b);
#else
return (fixed_t) (((int64_t) a << 16) / b);
#endif
}