1 2 /* @(#)s_ilogb.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 /* ieee_ilogb(double x) 15 * return the binary exponent of non-zero x 16 * ieee_ilogb(0) = 0x80000001 17 * ieee_ilogb(inf/NaN) = 0x7fffffff (no signal is raised) 18 */ 19 20 #include "fdlibm.h" 21 22 #ifdef __STDC__ 23 int ieee_ilogb(double x) 24 #else 25 int ieee_ilogb(x) 26 double x; 27 #endif 28 { 29 int hx,lx,ix; 30 31 hx = (__HI(x))&0x7fffffff; /* high word of x */ 32 if(hx<0x00100000) { 33 lx = __LO(x); 34 if((hx|lx)==0) 35 return 0x80000001; /* ieee_ilogb(0) = 0x80000001 */ 36 else /* subnormal x */ 37 if(hx==0) { 38 for (ix = -1043; lx>0; lx<<=1) ix -=1; 39 } else { 40 for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; 41 } 42 return ix; 43 } 44 else if (hx<0x7ff00000) return (hx>>20)-1023; 45 else return 0x7fffffff; 46 } 47
