1 /* @(#)s_logb.c 5.1 93/09/24 */ 2 /* 3 * ==================================================== 4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 5 * 6 * Developed at SunPro, a Sun Microsystems, Inc. business. 7 * Permission to use, copy, modify, and distribute this 8 * software is freely granted, provided that this notice 9 * is preserved. 10 * ==================================================== 11 */ 12 13 #ifndef lint 14 static char rcsid[] = "$FreeBSD$"; 15 #endif 16 17 /* 18 * double logb(x) 19 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. 20 * Use ilogb instead. 21 */ 22 23 #include "math.h" 24 #include "math_private.h" 25 26 #ifdef __STDC__ 27 double __generic_logb(double x) 28 #else 29 double __generic_logb(x) 30 double x; 31 #endif 32 { 33 int32_t lx,ix; 34 EXTRACT_WORDS(ix,lx,x); 35 ix &= 0x7fffffff; /* high |x| */ 36 if((ix|lx)==0) return -1.0/fabs(x); 37 if(ix>=0x7ff00000) return x*x; 38 if((ix>>=20)==0) /* IEEE 754 logb */ 39 return -1022.0; 40 else 41 return (double) (ix-1023); 42 } 43