1 /* @(#)s_ilogb.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 #include <sys/cdefs.h> 14 __FBSDID("$FreeBSD$"); 15 16 /* ilogb(double x) 17 * return the binary exponent of non-zero x 18 * ilogb(0) = FP_ILOGB0 19 * ilogb(NaN) = FP_ILOGBNAN (no signal is raised) 20 * ilogb(inf) = INT_MAX (no signal is raised) 21 */ 22 23 #include <limits.h> 24 25 #include "math.h" 26 #include "math_private.h" 27 28 int ilogb(double x) 29 { 30 int32_t hx,lx,ix; 31 32 EXTRACT_WORDS(hx,lx,x); 33 hx &= 0x7fffffff; 34 if(hx<0x00100000) { 35 if((hx|lx)==0) 36 return FP_ILOGB0; 37 else /* subnormal x */ 38 if(hx==0) { 39 for (ix = -1043; lx>0; lx<<=1) ix -=1; 40 } else { 41 for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; 42 } 43 return ix; 44 } 45 else if (hx<0x7ff00000) return (hx>>20)-1023; 46 else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN; 47 else return INT_MAX; 48 } 49
