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/* 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 <float.h> 21#include <math.h> 22 23#include "math_private.h" 24 25int 26ilogb(double x) 27{ 28 int32_t hx,lx,ix; 29 30 GET_HIGH_WORD(hx,x); 31 hx &= 0x7fffffff; 32 if(hx<0x00100000) { 33 GET_LOW_WORD(lx,x); 34 if((hx|lx)==0) 35 return FP_ILOGB0; /* ilogb(0) = FP_ILOGB0 */ 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 if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN; 46 else return INT_MAX; 47} 48DEF_STD(ilogb); 49LDBL_MAYBE_CLONE(ilogb); 50