1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22/*
23 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
24 */
25/*
26 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
27 * Use is subject to license terms.
28 */
29
30#pragma weak __asinh = asinh
31
32/* INDENT OFF */
33/*
34 * asinh(x)
35 * Method :
36 *	Based on
37 *		asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
38 *	we have
39 *	asinh(x) := x  if  1+x*x == 1,
40 *		 := sign(x)*(log(x)+ln2)) for large |x|, else
41 *		 := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x| > 2, else
42 *		 := sign(x)*log1p(|x|+x^2/(1+sqrt(1+x^2)))
43 */
44/* INDENT ON */
45
46#include "libm_macros.h"
47#include <math.h>
48
49static const double xxx[] = {
50/* one */	1.00000000000000000000e+00,	/* 3FF00000, 00000000 */
51/* ln2 */	6.93147180559945286227e-01,	/* 3FE62E42, FEFA39EF */
52/* huge */	1.00000000000000000000e+300
53};
54#define	one	xxx[0]
55#define	ln2	xxx[1]
56#define	huge	xxx[2]
57
58double
59asinh(double x) {
60	double t, w;
61	int hx, ix;
62
63	hx = ((int *) &x)[HIWORD];
64	ix = hx & 0x7fffffff;
65	if (ix >= 0x7ff00000)
66#if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
67		return (ix >= 0x7ff80000 ? x : x + x);
68		/* assumes sparc-like QNaN */
69#else
70		return (x + x);	/* x is inf or NaN */
71#endif
72	if (ix < 0x3e300000) {	/* |x|<2**-28 */
73		if (huge + x > one)
74			return (x);	/* return x inexact except 0 */
75	}
76	if (ix > 0x41b00000) {	/* |x| > 2**28 */
77		w = log(fabs(x)) + ln2;
78	} else if (ix > 0x40000000) {
79		/* 2**28 > |x| > 2.0 */
80		t = fabs(x);
81		w = log(2.0 * t + one / (sqrt(x * x + one) + t));
82	} else {
83		/* 2.0 > |x| > 2**-28 */
84		t = x * x;
85		w = log1p(fabs(x) + t / (one + sqrt(one + t)));
86	}
87	return (hx > 0 ? w : -w);
88}
89