139 lines
3.0 KiB
C
139 lines
3.0 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.
|
||
|
|
* ====================================================
|
||
|
|
*/
|
||
|
|
|
||
|
|
#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;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|