13a8617a8SJordan K. Hubbard /* @(#)s_logb.c 5.1 93/09/24 */ 23a8617a8SJordan K. Hubbard /* 33a8617a8SJordan K. Hubbard * ==================================================== 43a8617a8SJordan K. Hubbard * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 53a8617a8SJordan K. Hubbard * 63a8617a8SJordan K. Hubbard * Developed at SunPro, a Sun Microsystems, Inc. business. 73a8617a8SJordan K. Hubbard * Permission to use, copy, modify, and distribute this 83a8617a8SJordan K. Hubbard * software is freely granted, provided that this notice 93a8617a8SJordan K. Hubbard * is preserved. 103a8617a8SJordan K. Hubbard * ==================================================== 113a8617a8SJordan K. Hubbard */ 123a8617a8SJordan K. Hubbard 133a8617a8SJordan K. Hubbard #ifndef lint 147f3dea24SPeter Wemm static char rcsid[] = "$FreeBSD$"; 153a8617a8SJordan K. Hubbard #endif 163a8617a8SJordan K. Hubbard 173a8617a8SJordan K. Hubbard /* 183a8617a8SJordan K. Hubbard * double logb(x) 193a8617a8SJordan K. Hubbard * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. 203a8617a8SJordan K. Hubbard * Use ilogb instead. 213a8617a8SJordan K. Hubbard */ 223a8617a8SJordan K. Hubbard 233a8617a8SJordan K. Hubbard #include "math.h" 243a8617a8SJordan K. Hubbard #include "math_private.h" 253a8617a8SJordan K. Hubbard 2659b19ff1SAlfred Perlstein double 273819e840SPeter Wemm logb(double x) 283a8617a8SJordan K. Hubbard { 293a8617a8SJordan K. Hubbard int32_t lx,ix; 303a8617a8SJordan K. Hubbard EXTRACT_WORDS(ix,lx,x); 313a8617a8SJordan K. Hubbard ix &= 0x7fffffff; /* high |x| */ 323a8617a8SJordan K. Hubbard if((ix|lx)==0) return -1.0/fabs(x); 333a8617a8SJordan K. Hubbard if(ix>=0x7ff00000) return x*x; 343a8617a8SJordan K. Hubbard if((ix>>=20)==0) /* IEEE 754 logb */ 353a8617a8SJordan K. Hubbard return -1022.0; 363a8617a8SJordan K. Hubbard else 373a8617a8SJordan K. Hubbard return (double) (ix-1023); 383a8617a8SJordan K. Hubbard } 39