1 2 /* @(#)s_logb.c 1.3 95/01/18 */ 3 /* 4 * ==================================================== 5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6 * 7 * Developed at SunSoft, a Sun Microsystems, Inc. business. 8 * Permission to use, copy, modify, and distribute this 9 * software is freely granted, provided that this notice 10 * is preserved. 11 * ==================================================== 12 */ 13 14 /* 15 * double ieee_logb(x) 16 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. 17 * Use ilogb instead. 18 */ 19 20 #include "fdlibm.h" 21 22 #ifdef __STDC__ ieee_logb(double x)23 double ieee_logb(double x) 24 #else 25 double ieee_logb(x) 26 double x; 27 #endif 28 { 29 int lx,ix; 30 ix = (__HI(x))&0x7fffffff; /* high |x| */ 31 lx = __LO(x); /* low x */ 32 if((ix|lx)==0) return -1.0/ieee_fabs(x); 33 if(ix>=0x7ff00000) return x*x; 34 if((ix>>=20)==0) /* IEEE 754 logb */ 35 return -1022.0; 36 else 37 return (double) (ix-1023); 38 } 39