diff options
Diffstat (limited to 'lib/msun/src/s_logb.c')
-rw-r--r-- | lib/msun/src/s_logb.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/lib/msun/src/s_logb.c b/lib/msun/src/s_logb.c new file mode 100644 index 0000000000000..49b842f9d3322 --- /dev/null +++ b/lib/msun/src/s_logb.c @@ -0,0 +1,48 @@ +/* @(#)s_logb.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. + * ==================================================== + */ + +#ifndef lint +static char rcsid[] = "$Id: s_logb.c,v 1.1.1.1 1994/05/06 00:20:06 gclarkii Exp $"; +#endif + +/* + * double logb(x) + * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. + * Use ilogb instead. + */ + +#include "math.h" +#include <machine/endian.h> + +#if BYTE_ORDER == LITTLE_ENDIAN +#define n0 1 +#else +#define n0 0 +#endif + +#ifdef __STDC__ + double logb(double x) +#else + double logb(x) + double x; +#endif +{ + int lx,ix; + ix = (*(n0+(int*)&x))&0x7fffffff; /* high |x| */ + lx = *(1-n0+(int*)&x); /* low x */ + if((ix|lx)==0) return -1.0/fabs(x); + if(ix>=0x7ff00000) return x*x; + if((ix>>=20)==0) /* IEEE 754 logb */ + return -1022.0; + else + return (double) (ix-1023); +} |