1 /* 2 * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 /* ilogb(double x) 27 * return the binary exponent of non-zero x 28 * ilogb(0) = 0x80000001 29 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised) 30 */ 31 32 #include "fdlibm.h" 33 34 #ifdef __STDC__ ilogb(double x)35 int ilogb(double x) 36 #else 37 int ilogb(x) 38 double x; 39 #endif 40 { 41 int hx,lx,ix; 42 43 hx = (__HI(x))&0x7fffffff; /* high word of x */ 44 if(hx<0x00100000) { 45 lx = __LO(x); 46 if((hx|lx)==0) 47 return 0x80000001; /* ilogb(0) = 0x80000001 */ 48 else /* subnormal x */ 49 if(hx==0) { 50 for (ix = -1043; lx>0; lx<<=1) ix -=1; 51 } else { 52 for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1; 53 } 54 return ix; 55 } 56 else if (hx<0x7ff00000) return (hx>>20)-1023; 57 else return 0x7fffffff; 58 } 59