mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-22 21:10:07 +00:00
60 lines
1.5 KiB
C
60 lines
1.5 KiB
C
/* @(#)s_ilogb.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.
|
|
* ====================================================
|
|
*/
|
|
|
|
#if defined(LIBM_SCCS) && !defined(lint)
|
|
static char rcsid[] = "$NetBSD: s_ilogb.c,v 1.9 1995/05/10 20:47:28 jtc Exp $";
|
|
#endif
|
|
|
|
/* ilogb(double x)
|
|
* return the binary exponent of non-zero x
|
|
* ilogb(0) = FP_ILOGB0
|
|
* ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
|
|
* ilogb(+-Inf) = INT_MAX (no signal is raised)
|
|
*/
|
|
|
|
#include <limits.h>
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
|
|
int __ilogb(double x)
|
|
{
|
|
int32_t hx,lx,ix;
|
|
|
|
GET_HIGH_WORD(hx,x);
|
|
hx &= 0x7fffffff;
|
|
if(hx<0x00100000) {
|
|
GET_LOW_WORD(lx,x);
|
|
if((hx|lx)==0)
|
|
return FP_ILOGB0; /* ilogb(0) = FP_ILOGB0 */
|
|
else /* subnormal x */
|
|
if(hx==0) {
|
|
for (ix = -1043; lx>0; lx<<=1) ix -=1;
|
|
} else {
|
|
for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
|
|
}
|
|
return ix;
|
|
}
|
|
else if (hx<0x7ff00000) return (hx>>20)-1023;
|
|
else if (FP_ILOGBNAN != INT_MAX) {
|
|
/* ISO C99 requires ilogb(+-Inf) == INT_MAX. */
|
|
GET_LOW_WORD(lx,x);
|
|
if(((hx^0x7ff00000)|lx) == 0)
|
|
return INT_MAX;
|
|
}
|
|
return FP_ILOGBNAN;
|
|
}
|
|
weak_alias (__ilogb, ilogb)
|
|
#ifdef NO_LONG_DOUBLE
|
|
strong_alias (__ilogb, __ilogbl)
|
|
weak_alias (__ilogb, ilogbl)
|
|
#endif
|