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/* @(#)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.
* ====================================================
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
/*
* modf(double x, double *iptr)
* return fraction part of x, and return x's integral part in *iptr.
* Method:
* Bit twiddling.
*
* Exception:
* No exception.
*/
#include <sys/types.h>
#include <machine/endian.h>
#include <math.h>
/* Bit fiddling routines copied from msun/src/math_private.h,v 1.15 */
#if BYTE_ORDER == BIG_ENDIAN
typedef union
{
double value;
struct
{
u_int32_t msw;
u_int32_t lsw;
} parts;
} ieee_double_shape_type;
#endif
#if BYTE_ORDER == LITTLE_ENDIAN
typedef union
{
double value;
struct
{
u_int32_t lsw;
u_int32_t msw;
} parts;
} 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)
/* 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)
static const double one = 1.0;
double
modf(double x, double *iptr)
{
int32_t i0,i1,j0;
u_int32_t i;
EXTRACT_WORDS(i0,i1,x);
j0 = ((i0>>20)&0x7ff)-0x3ff; /* exponent of x */
if(j0<20) { /* integer part in high x */
if(j0<0) { /* |x|<1 */
INSERT_WORDS(*iptr,i0&0x80000000,0); /* *iptr = +-0 */
return x;
} else {
i = (0x000fffff)>>j0;
if(((i0&i)|i1)==0) { /* x is integral */
u_int32_t high;
*iptr = x;
GET_HIGH_WORD(high,x);
INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
return x;
} else {
INSERT_WORDS(*iptr,i0&(~i),0);
return x - *iptr;
}
}
} else if (j0>51) { /* no fraction part */
u_int32_t high;
if (j0 == 0x400) { /* inf/NaN */
*iptr = x;
return 0.0 / x;
}
*iptr = x*one;
GET_HIGH_WORD(high,x);
INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
return x;
} else { /* fraction part in low x */
i = ((u_int32_t)(0xffffffff))>>(j0-20);
if((i1&i)==0) { /* x is integral */
u_int32_t high;
*iptr = x;
GET_HIGH_WORD(high,x);
INSERT_WORDS(x,high&0x80000000,0); /* return +-0 */
return x;
} else {
INSERT_WORDS(*iptr,i0,i1&(~i));
return x - *iptr;
}
}
}
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