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 /*
  27  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __sinh = sinh
  32 
  33 
  34 /*
  35  * sinh(x)
  36  * Code originated from 4.3bsd.
  37  * Modified by K.C. Ng for SUN 4.0 libm.
  38  * Method :
  39  *      1. reduce x to non-negative by sinh(-x) = - sinh(x).
  40  *      2.
  41  *
  42  *                                   expm1(x) + expm1(x)/(expm1(x)+1)
  43  *   0 <= x <= lnovft   : sinh(x) := --------------------------------
  44  *                                                                     2
  45  *  lnovft <= x <  INF  : sinh(x) := exp(x-1024*ln2)*2**1023
  46  *
  47  *
  48  * Special cases:
  49  *      sinh(x) is x if x is +INF, -INF, or NaN.
  50  *      only sinh(0)=0 is exact for finite argument.
  51  *
  52  */
  53 
  54 #include "libm.h"
  55 
  56 static const double ln2hi = 6.93147180369123816490e-01,
  57         ln2lo = 1.90821492927058770002e-10,
  58         lnovft = 7.09782712893383973096e+02;
  59 
  60 double
  61 sinh(double x)
  62 {
  63         double ox, r, t;
  64 
  65         ox = x;
  66         r = fabs(x);
  67 
  68         if (!finite(x))
  69                 return (x * r);
  70 
  71         if (r < lnovft) {
  72                 t = expm1(r);
  73                 r = copysign((t + t / (1.0 + t)) * 0.5, x);
  74         } else {
  75                 if (r < 1000.0)
  76                         x = copysign(exp((r - 1024 * ln2hi) - 1024 * ln2lo), x);
  77 
  78                 r = scalbn(x, 1023);
  79         }
  80 
  81         if (!finite(r))
  82                 r = _SVID_libm_err(ox, ox, 25);
  83 
  84         return (r);
  85 }