frodo-wii/Src/FixPoint.h
2009-01-13 18:46:42 +00:00

434 lines
12 KiB
C++

/*
* FixPoint.h - Provides fixed point arithmetic (for use in SID.cpp)
*
* (C) 1997 Andreas Dehmel
*
* Frodo (C) 1994-1997,2002-2005 Christian Bauer
*
* 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
*/
/*
* You need to define FIXPOINT_PREC (number of fractional bits) and
* ldSINTAB (ld of the size of the sinus table) as well M_PI
* _before_ including this file.
* Requires at least 32bit ints!
*/
#define FIXPOINT_BITS 32
// Sign-bit
#define FIXPOINT_SIGN (1<<(FIXPOINT_BITS-1))
/*
* Elementary functions for the FixPoint class
*/
// Multiplies two fixpoint numbers, result is a fixpoint number.
static inline int fixmult(int x, int y)
{
register unsigned int a,b;
register bool sign;
sign = (x ^ y) < 0;
if (x < 0) {x = -x;}
if (y < 0) {y = -y;}
// a, b : integer part; x, y : fractional part. All unsigned now (for shift right)!!!
a = (((unsigned int)x) >> FIXPOINT_PREC); x &= ~(a << FIXPOINT_PREC);
b = (((unsigned int)y) >> FIXPOINT_PREC); y &= ~(b << FIXPOINT_PREC);
x = ((a*b) << FIXPOINT_PREC) + (a*y + b*x) +
((unsigned int)((x*y) + (1 << (FIXPOINT_PREC-1))) >> FIXPOINT_PREC);
#ifdef FIXPOINT_SIGN
if (x < 0) {x ^= FIXPOINT_SIGN;}
#endif
if (sign) {x = -x;}
return(x);
}
// Multiplies a fixpoint number with an integer, result is a 32 bit (!) integer in
// contrast to using the standard member-functions which can provide only (32-FIXPOINT_PREC)
// valid bits.
static inline int intmult(int x, int y) // x is fixpoint, y integer
{
register unsigned int i,j;
register bool sign;
sign = (x ^ y) < 0;
if (x < 0) {x = -x;}
if (y < 0) {y = -y;}
i = (((unsigned int)x) >> 16); x &= ~(i << 16); // split both into 16.16 parts
j = (((unsigned int)y) >> 16); y &= ~(j << 16);
#if FIXPOINT_PREC <= 16
// This '32' is independent of the number of bits used, it's due to the 16 bit shift
i = ((i*j) << (32 - FIXPOINT_PREC)) + ((i*y + j*x) << (16 - FIXPOINT_PREC)) +
((unsigned int)(x*y + (1 << (FIXPOINT_PREC - 1))) >> FIXPOINT_PREC);
#else
{
register unsigned int h;
h = (i*y + j*x);
i = ((i*j) << (32 - FIXPOINT_PREC)) + (h >> (FIXPOINT_PREC - 16));
h &= ((1 << (FIXPOINT_PREC - 16)) - 1); x *= y;
i += (x >> FIXPOINT_PREC); x &= ((1 << FIXPOINT_PREC) - 1);
i += (((h + (x >> 16)) + (1 << (FIXPOINT_PREC - 17))) >> (FIXPOINT_PREC - 16));
}
#endif
#ifdef FIXPOINT_SIGN
if (i < 0) {i ^= FIXPOINT_SIGN;}
#endif
if (sign) {i = -i;}
return(i);
}
// Computes the product of a fixpoint number with itself.
static inline int fixsquare(int x)
{
register unsigned int a;
if (x < 0) {x = -x;}
a = (((unsigned int)x) >> FIXPOINT_PREC); x &= ~(a << FIXPOINT_PREC);
x = ((a*a) << FIXPOINT_PREC) + ((a*x) << 1) +
((unsigned int)((x*x) + (1 << (FIXPOINT_PREC-1))) >> FIXPOINT_PREC);
#ifdef FIXPOINT_SIGN
if (x < 0) {x ^= FIXPOINT_SIGN;}
#endif
return(x);
}
// Computes the square root of a fixpoint number.
static inline int fixsqrt(int x)
{
register int test, step;
if (x < 0) return(-1); if (x == 0) return(0);
step = (x <= (1<<FIXPOINT_PREC)) ? (1<<FIXPOINT_PREC) : (1<<((FIXPOINT_BITS - 2 + FIXPOINT_PREC)>>1));
test = 0;
while (step != 0)
{
register int h;
h = fixsquare(test + step);
if (h <= x) {test += step;}
if (h == x) break;
step >>= 1;
}
return(test);
}
// Divides a fixpoint number by another fixpoint number, yielding a fixpoint result.
static inline int fixdiv(int x, int y)
{
register int res, mask;
register bool sign;
sign = (x ^ y) < 0;
if (x < 0) {x = -x;}
if (y < 0) {y = -y;}
mask = (1<<FIXPOINT_PREC); res = 0;
while (x > y) {y <<= 1; mask <<= 1;}
while (mask != 0)
{
if (x >= y) {res |= mask; x -= y;}
mask >>= 1; y >>= 1;
}
#ifdef FIXPOINT_SIGN
if (res < 0) {res ^= FIXPOINT_SIGN;}
#endif
if (sign) {res = -res;}
return(res);
}
/*
* The C++ Fixpoint class. By no means exhaustive...
* Since it contains only one int data, variables of type FixPoint can be
* passed directly rather than as a reference.
*/
class FixPoint
{
private:
int x;
public:
FixPoint(void);
FixPoint(int y);
~FixPoint(void);
// conversions
int Value(void);
int round(void);
operator int(void);
// unary operators
FixPoint sqrt(void);
FixPoint sqr(void);
FixPoint abs(void);
FixPoint operator+(void);
FixPoint operator-(void);
FixPoint operator++(void);
FixPoint operator--(void);
// binary operators
int imul(int y);
FixPoint operator=(FixPoint y);
FixPoint operator=(int y);
FixPoint operator+(FixPoint y);
FixPoint operator+(int y);
FixPoint operator-(FixPoint y);
FixPoint operator-(int y);
FixPoint operator/(FixPoint y);
FixPoint operator/(int y);
FixPoint operator*(FixPoint y);
FixPoint operator*(int y);
FixPoint operator+=(FixPoint y);
FixPoint operator+=(int y);
FixPoint operator-=(FixPoint y);
FixPoint operator-=(int y);
FixPoint operator*=(FixPoint y);
FixPoint operator*=(int y);
FixPoint operator/=(FixPoint y);
FixPoint operator/=(int y);
FixPoint operator<<(int y);
FixPoint operator>>(int y);
FixPoint operator<<=(int y);
FixPoint operator>>=(int y);
// conditional operators
bool operator<(FixPoint y);
bool operator<(int y);
bool operator<=(FixPoint y);
bool operator<=(int y);
bool operator>(FixPoint y);
bool operator>(int y);
bool operator>=(FixPoint y);
bool operator>=(int y);
bool operator==(FixPoint y);
bool operator==(int y);
bool operator!=(FixPoint y);
bool operator!=(int y);
};
/*
* int gets treated differently according to the case:
*
* a) Equations (=) or condition checks (==, <, <= ...): raw int (i.e. no conversion)
* b) As an argument for an arithmetic operation: conversion to fixpoint by shifting
*
* Otherwise loading meaningful values into FixPoint variables would be very awkward.
*/
FixPoint::FixPoint(void) {x = 0;}
FixPoint::FixPoint(int y) {x = y;}
FixPoint::~FixPoint(void) {;}
inline int FixPoint::Value(void) {return(x);}
inline int FixPoint::round(void) {return((x + (1 << (FIXPOINT_PREC-1))) >> FIXPOINT_PREC);}
inline FixPoint::operator int(void) {return(x);}
// unary operators
inline FixPoint FixPoint::sqrt(void) {return(fixsqrt(x));}
inline FixPoint FixPoint::sqr(void) {return(fixsquare(x));}
inline FixPoint FixPoint::abs(void) {return((x < 0) ? -x : x);}
inline FixPoint FixPoint::operator+(void) {return(x);}
inline FixPoint FixPoint::operator-(void) {return(-x);}
inline FixPoint FixPoint::operator++(void) {x += (1 << FIXPOINT_PREC); return x;}
inline FixPoint FixPoint::operator--(void) {x -= (1 << FIXPOINT_PREC); return x;}
// binary operators
inline int FixPoint::imul(int y) {return(intmult(x,y));}
inline FixPoint FixPoint::operator=(FixPoint y) {x = y.Value(); return x;}
inline FixPoint FixPoint::operator=(int y) {x = y; return x;}
inline FixPoint FixPoint::operator+(FixPoint y) {return(x + y.Value());}
inline FixPoint FixPoint::operator+(int y) {return(x + (y << FIXPOINT_PREC));}
inline FixPoint FixPoint::operator-(FixPoint y) {return(x - y.Value());}
inline FixPoint FixPoint::operator-(int y) {return(x - (y << FIXPOINT_PREC));}
inline FixPoint FixPoint::operator/(FixPoint y) {return(fixdiv(x,y.Value()));}
inline FixPoint FixPoint::operator/(int y) {return(x/y);}
inline FixPoint FixPoint::operator*(FixPoint y) {return(fixmult(x,y.Value()));}
inline FixPoint FixPoint::operator*(int y) {return(x*y);}
inline FixPoint FixPoint::operator+=(FixPoint y) {x += y.Value(); return x;}
inline FixPoint FixPoint::operator+=(int y) {x += (y << FIXPOINT_PREC); return x;}
inline FixPoint FixPoint::operator-=(FixPoint y) {x -= y.Value(); return x;}
inline FixPoint FixPoint::operator-=(int y) {x -= (y << FIXPOINT_PREC); return x;}
inline FixPoint FixPoint::operator*=(FixPoint y) {x = fixmult(x,y.Value()); return x;}
inline FixPoint FixPoint::operator*=(int y) {x *= y; return x;}
inline FixPoint FixPoint::operator/=(FixPoint y) {x = fixdiv(x,y.Value()); return x;}
inline FixPoint FixPoint::operator/=(int y) {x /= y; return x;}
inline FixPoint FixPoint::operator<<(int y) {return(x << y);}
inline FixPoint FixPoint::operator>>(int y) {return(x >> y);}
inline FixPoint FixPoint::operator<<=(int y) {x <<= y; return x;}
inline FixPoint FixPoint::operator>>=(int y) {x >>= y; return x;}
// conditional operators
inline bool FixPoint::operator<(FixPoint y) {return(x < y.Value());}
inline bool FixPoint::operator<(int y) {return(x < y);}
inline bool FixPoint::operator<=(FixPoint y) {return(x <= y.Value());}
inline bool FixPoint::operator<=(int y) {return(x <= y);}
inline bool FixPoint::operator>(FixPoint y) {return(x > y.Value());}
inline bool FixPoint::operator>(int y) {return(x > y);}
inline bool FixPoint::operator>=(FixPoint y) {return(x >= y.Value());}
inline bool FixPoint::operator>=(int y) {return(x >= y);}
inline bool FixPoint::operator==(FixPoint y) {return(x == y.Value());}
inline bool FixPoint::operator==(int y) {return(x == y);}
inline bool FixPoint::operator!=(FixPoint y) {return(x != y.Value());}
inline bool FixPoint::operator!=(int y) {return(x != y);}
/*
* In case the first argument is an int (i.e. member-operators not applicable):
* Not supported: things like int/FixPoint. The same difference in conversions
* applies as mentioned above.
*/
// binary operators
inline FixPoint operator+(int x, FixPoint y) {return((x << FIXPOINT_PREC) + y.Value());}
inline FixPoint operator-(int x, FixPoint y) {return((x << FIXPOINT_PREC) - y.Value());}
inline FixPoint operator*(int x, FixPoint y) {return(x*y.Value());}
// conditional operators
inline bool operator==(int x, FixPoint y) {return(x == y.Value());}
inline bool operator!=(int x, FixPoint y) {return(x != y.Value());}
inline bool operator<(int x, FixPoint y) {return(x < y.Value());}
inline bool operator<=(int x, FixPoint y) {return(x <= y.Value());}
inline bool operator>(int x, FixPoint y) {return(x > y.Value());}
inline bool operator>=(int x, FixPoint y) {return(x >= y.Value());}
/*
* For more convenient creation of constant fixpoint numbers from constant floats.
*/
#define FixNo(n) (FixPoint)((int)(n*(1<<FIXPOINT_PREC)))
/*
* Stuff re. the sinus table used with fixpoint arithmetic
*/
// define as global variable
FixPoint SinTable[(1<<ldSINTAB)];
#define FIXPOINT_SIN_COS_GENERIC \
if (angle >= 3*(1<<ldSINTAB)) {return(-SinTable[(1<<(ldSINTAB+2)) - angle]);}\
if (angle >= 2*(1<<ldSINTAB)) {return(-SinTable[angle - 2*(1<<ldSINTAB)]);}\
if (angle >= (1<<ldSINTAB)) {return(SinTable[2*(1<<ldSINTAB) - angle]);}\
return(SinTable[angle]);
// sin and cos: angle is fixpoint number 0 <= angle <= 2 (*PI)
static inline FixPoint fixsin(FixPoint x)
{
int angle = x;
angle = (angle >> (FIXPOINT_PREC - ldSINTAB - 1)) & ((1<<(ldSINTAB+2))-1);
FIXPOINT_SIN_COS_GENERIC
}
static inline FixPoint fixcos(FixPoint x)
{
int angle = x;
// cos(x) = sin(x+PI/2)
angle = (angle + (1<<(FIXPOINT_PREC-1)) >> (FIXPOINT_PREC - ldSINTAB - 1)) & ((1<<(ldSINTAB+2))-1);
FIXPOINT_SIN_COS_GENERIC
}
static inline void InitFixSinTab(void)
{
int i;
float step;
for (i=0, step=0; i<(1<<ldSINTAB); i++, step+=0.5/(1<<ldSINTAB))
{
SinTable[i] = FixNo(sin(M_PI * step));
}
}