125c28e83SPiotr Jasiukajtis /* 225c28e83SPiotr Jasiukajtis * CDDL HEADER START 325c28e83SPiotr Jasiukajtis * 425c28e83SPiotr Jasiukajtis * The contents of this file are subject to the terms of the 525c28e83SPiotr Jasiukajtis * Common Development and Distribution License (the "License"). 625c28e83SPiotr Jasiukajtis * You may not use this file except in compliance with the License. 725c28e83SPiotr Jasiukajtis * 825c28e83SPiotr Jasiukajtis * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 925c28e83SPiotr Jasiukajtis * or http://www.opensolaris.org/os/licensing. 1025c28e83SPiotr Jasiukajtis * See the License for the specific language governing permissions 1125c28e83SPiotr Jasiukajtis * and limitations under the License. 1225c28e83SPiotr Jasiukajtis * 1325c28e83SPiotr Jasiukajtis * When distributing Covered Code, include this CDDL HEADER in each 1425c28e83SPiotr Jasiukajtis * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 1525c28e83SPiotr Jasiukajtis * If applicable, add the following below this CDDL HEADER, with the 1625c28e83SPiotr Jasiukajtis * fields enclosed by brackets "[]" replaced with your own identifying 1725c28e83SPiotr Jasiukajtis * information: Portions Copyright [yyyy] [name of copyright owner] 1825c28e83SPiotr Jasiukajtis * 1925c28e83SPiotr Jasiukajtis * CDDL HEADER END 2025c28e83SPiotr Jasiukajtis */ 2125c28e83SPiotr Jasiukajtis 2225c28e83SPiotr Jasiukajtis /* 2325c28e83SPiotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 2425c28e83SPiotr Jasiukajtis */ 2525c28e83SPiotr Jasiukajtis /* 2625c28e83SPiotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 2725c28e83SPiotr Jasiukajtis * Use is subject to license terms. 2825c28e83SPiotr Jasiukajtis */ 2925c28e83SPiotr Jasiukajtis 3025c28e83SPiotr Jasiukajtis /* 3125c28e83SPiotr Jasiukajtis * log2l(x) 3225c28e83SPiotr Jasiukajtis * RETURN THE BASE 2 LOGARITHM OF X 3325c28e83SPiotr Jasiukajtis * 3425c28e83SPiotr Jasiukajtis * Method: 3525c28e83SPiotr Jasiukajtis * purge off 0,INF, and NaN. 3625c28e83SPiotr Jasiukajtis * n = ilogb(x) 3725c28e83SPiotr Jasiukajtis * if (n<0) n+=1 3825c28e83SPiotr Jasiukajtis * z = scalbn(x,-n) 3925c28e83SPiotr Jasiukajtis * LOG2(x) = n + (1/ln2)*log(x) 4025c28e83SPiotr Jasiukajtis */ 4125c28e83SPiotr Jasiukajtis 42*ddc0e0b5SRichard Lowe #pragma weak __log2l = log2l 4325c28e83SPiotr Jasiukajtis 4425c28e83SPiotr Jasiukajtis #include "libm.h" 4525c28e83SPiotr Jasiukajtis #include "longdouble.h" 4625c28e83SPiotr Jasiukajtis 4725c28e83SPiotr Jasiukajtis static const long double 4825c28e83SPiotr Jasiukajtis zero = 0.0L, 4925c28e83SPiotr Jasiukajtis half = 0.5L, 5025c28e83SPiotr Jasiukajtis one = 1.0L, 5125c28e83SPiotr Jasiukajtis invln2 = 1.442695040888963407359924681001892137427e+0000L; 5225c28e83SPiotr Jasiukajtis 5325c28e83SPiotr Jasiukajtis long double 5425c28e83SPiotr Jasiukajtis log2l(long double x) { 5525c28e83SPiotr Jasiukajtis int n; 5625c28e83SPiotr Jasiukajtis 5725c28e83SPiotr Jasiukajtis if (x == zero || !finitel(x)) 5825c28e83SPiotr Jasiukajtis return (logl(x)); 5925c28e83SPiotr Jasiukajtis n = ilogbl(x); 6025c28e83SPiotr Jasiukajtis if (n < 0) 6125c28e83SPiotr Jasiukajtis n += 1; 6225c28e83SPiotr Jasiukajtis x = scalbnl(x, -n); 6325c28e83SPiotr Jasiukajtis if (x == half) 6425c28e83SPiotr Jasiukajtis return (n - one); 6525c28e83SPiotr Jasiukajtis return (n + invln2 * logl(x)); 6625c28e83SPiotr Jasiukajtis } 67