1 /* 2 * ==================================================== 3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 4 * 5 * Developed at SunPro, a Sun Microsystems, Inc. business. 6 * Permission to use, copy, modify, and distribute this 7 * software is freely granted, provided that this notice 8 * is preserved. 9 * ==================================================== 10 */ 11 12 #include <sys/cdefs.h> 13 /* ilogb(double x) 14 * return the binary exponent of non-zero x 15 * ilogb(0) = FP_ILOGB0 16 * ilogb(NaN) = FP_ILOGBNAN (no signal is raised) 17 * ilogb(inf) = INT_MAX (no signal is raised) 18 */ 19 20 #include <limits.h> 21 22 #include "math.h" 23 #include "math_private.h" 24 25 int ilogb(double x) 26 { 27 int32_t hx,lx,ix; 28 29 EXTRACT_WORDS(hx,lx,x); 30 hx &= 0x7fffffff; 31 if(hx<0x00100000) { 32 if((hx|lx)==0) 33 return FP_ILOGB0; 34 else /* subnormal x */ 35 if(hx==0) { 36 for (ix = -1043; lx>0; lx<<=1) ix -=1; 37 } else { 38 for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; 39 } 40 return ix; 41 } 42 else if (hx<0x7ff00000) return (hx>>20)-1023; 43 else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN; 44 else return INT_MAX; 45 } 46