1*1e651e1eSRoland Levillain 2*1e651e1eSRoland Levillain /* @(#)s_logb.c 1.3 95/01/18 */ 3*1e651e1eSRoland Levillain /* 4*1e651e1eSRoland Levillain * ==================================================== 5*1e651e1eSRoland Levillain * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 6*1e651e1eSRoland Levillain * 7*1e651e1eSRoland Levillain * Developed at SunSoft, a Sun Microsystems, Inc. business. 8*1e651e1eSRoland Levillain * Permission to use, copy, modify, and distribute this 9*1e651e1eSRoland Levillain * software is freely granted, provided that this notice 10*1e651e1eSRoland Levillain * is preserved. 11*1e651e1eSRoland Levillain * ==================================================== 12*1e651e1eSRoland Levillain */ 13*1e651e1eSRoland Levillain 14*1e651e1eSRoland Levillain /* 15*1e651e1eSRoland Levillain * double ieee_logb(x) 16*1e651e1eSRoland Levillain * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. 17*1e651e1eSRoland Levillain * Use ilogb instead. 18*1e651e1eSRoland Levillain */ 19*1e651e1eSRoland Levillain 20*1e651e1eSRoland Levillain #include "fdlibm.h" 21*1e651e1eSRoland Levillain 22*1e651e1eSRoland Levillain #ifdef __STDC__ ieee_logb(double x)23*1e651e1eSRoland Levillain double ieee_logb(double x) 24*1e651e1eSRoland Levillain #else 25*1e651e1eSRoland Levillain double ieee_logb(x) 26*1e651e1eSRoland Levillain double x; 27*1e651e1eSRoland Levillain #endif 28*1e651e1eSRoland Levillain { 29*1e651e1eSRoland Levillain int lx,ix; 30*1e651e1eSRoland Levillain ix = (__HI(x))&0x7fffffff; /* high |x| */ 31*1e651e1eSRoland Levillain lx = __LO(x); /* low x */ 32*1e651e1eSRoland Levillain if((ix|lx)==0) return -1.0/ieee_fabs(x); 33*1e651e1eSRoland Levillain if(ix>=0x7ff00000) return x*x; 34*1e651e1eSRoland Levillain if((ix>>=20)==0) /* IEEE 754 logb */ 35*1e651e1eSRoland Levillain return -1022.0; 36*1e651e1eSRoland Levillain else 37*1e651e1eSRoland Levillain return (double) (ix-1023); 38*1e651e1eSRoland Levillain } 39