ref: 53aac62a54ebbcc1781c0000d3e2384ed038c7bb
dir: /libmath/fdlibm/s_ilogb.c/
/* derived from /netlib/fdlibm */ /* @(#)s_ilogb.c 1.3 95/01/18 */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ /* ilogb(double x) * return the binary exponent of non-zero x * ilogb(0) = 0x80000001 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised) */ #include "fdlibm.h" int ilogb(double x) { int hx,lx,ix; hx = (__HI(x))&0x7fffffff; /* high word of x */ if(hx<0x00100000) { lx = __LO(x); if((hx|lx)==0) return 0x80000001; /* ilogb(0) = 0x80000001 */ else /* subnormal x */ if(hx==0) { for (ix = -1043; lx>0; lx<<=1) ix -=1; } else { for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; } return ix; } else if (hx<0x7ff00000) return (hx>>20)-1023; else return 0x7fffffff; }