reactos/lib/sdk/crt/math/s_modf.c
Amine Khaldi c424146e2c Create a branch for cmake bringup.
svn path=/branches/cmake-bringup/; revision=48236
2010-07-24 18:52:44 +00:00

194 lines
4.2 KiB
C

/* @(#)s_modf.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
FUNCTION
<<modf>>, <<modff>>---split fractional and integer parts
INDEX
modf
INDEX
modff
ANSI_SYNOPSIS
#include <math.h>
double modf(double <[val]>, double *<[ipart]>);
float modff(float <[val]>, float *<[ipart]>);
TRAD_SYNOPSIS
#include <math.h>
double modf(<[val]>, <[ipart]>)
double <[val]>;
double *<[ipart]>;
float modff(<[val]>, <[ipart]>)
float <[val]>;
float *<[ipart]>;
DESCRIPTION
<<modf>> splits the double <[val]> apart into an integer part
and a fractional part, returning the fractional part and
storing the integer part in <<*<[ipart]>>>. No rounding
whatsoever is done; the sum of the integer and fractional
parts is guaranteed to be exactly equal to <[val]>. That
is, if . <[realpart]> = modf(<[val]>, &<[intpart]>); then
`<<<[realpart]>+<[intpart]>>>' is the same as <[val]>.
<<modff>> is identical, save that it takes and returns
<<float>> rather than <<double>> values.
RETURNS
The fractional part is returned. Each result has the same
sign as the supplied argument <[val]>.
PORTABILITY
<<modf>> is ANSI C. <<modff>> is an extension.
QUICKREF
modf ansi pure
modff - pure
*/
/*
* modf(double x, double *iptr)
* return fraction part of x, and return x's integral part in *iptr.
* Method:
* Bit twiddling.
*
* Exception:
* No exception.
*/
static const double one = 1.0;
#define __int32_t long
#define __uint32_t unsigned long
#define __IEEE_LITTLE_ENDIAN
#ifdef __IEEE_BIG_ENDIAN
typedef union
{
struct
{
__uint32_t msw;
__uint32_t lsw;
} parts;
double value;
} ieee_double_shape_type;
#endif
#ifdef __IEEE_LITTLE_ENDIAN
typedef union
{
struct
{
__uint32_t lsw;
__uint32_t msw;
} parts;
double value;
} ieee_double_shape_type;
#endif
/* Get two 32 bit ints from a double. */
#define EXTRACT_WORDS(ix0,ix1,d) \
do { \
ieee_double_shape_type ew_u; \
ew_u.value = (d); \
(ix0) = ew_u.parts.msw; \
(ix1) = ew_u.parts.lsw; \
} while (0)
/* Get the more significant 32 bit int from a double. */
#define GET_HIGH_WORD(i,d) \
do { \
ieee_double_shape_type gh_u; \
gh_u.value = (d); \
(i) = gh_u.parts.msw; \
} while (0)
/* Get the less significant 32 bit int from a double. */
#define GET_LOW_WORD(i,d) \
do { \
ieee_double_shape_type gl_u; \
gl_u.value = (d); \
(i) = gl_u.parts.lsw; \
} while (0)
/* Set a double from two 32 bit ints. */
#define INSERT_WORDS(d,ix0,ix1) \
do { \
ieee_double_shape_type iw_u; \
iw_u.parts.msw = (ix0); \
iw_u.parts.lsw = (ix1); \
(d) = iw_u.value; \
} while (0)
double modf(double x, double *iptr)
{
__int32_t i0,i1,j_0;
__uint32_t i;
EXTRACT_WORDS(i0,i1,x);
j_0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
if(j_0<20) { /* integer part in high x */
if(j_0<0) { /* |x|<1 */
INSERT_WORDS(*iptr,i0&0x80000000U,0); /* *iptr = +-0 */
return x;
} else {
i = (0x000fffff)>>j_0;
if(((i0&i)|i1)==0) { /* x is integral */
__uint32_t high;
*iptr = x;
GET_HIGH_WORD(high,x);
INSERT_WORDS(x,high&0x80000000U,0); /* return +-0 */
return x;
} else {
INSERT_WORDS(*iptr,i0&(~i),0);
return x - *iptr;
}
}
} else if (j_0>51) { /* no fraction part */
__uint32_t high;
*iptr = x*one;
GET_HIGH_WORD(high,x);
INSERT_WORDS(x,high&0x80000000U,0); /* return +-0 */
return x;
} else { /* fraction part in low x */
i = ((__uint32_t)(0xffffffffU))>>(j_0-20);
if((i1&i)==0) { /* x is integral */
__uint32_t high;
*iptr = x;
GET_HIGH_WORD(high,x);
INSERT_WORDS(x,high&0x80000000U,0); /* return +-0 */
return x;
} else {
INSERT_WORDS(*iptr,i0,i1&(~i));
return x - *iptr;
}
}
}
//#endif /* _DOUBLE_IS_32BITS */