/****************************************************************************
 *
 * $Source: /usr/local/cvsroot/gccsdk/unixlib/source/math/asinh.c,v $
 * $Date: 2001/01/29 15:10:19 $
 * $Revision: 1.2 $
 * $State: Exp $
 * $Author: admin $
 *
 ***************************************************************************/

/* @(#)s_asinh.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: s_asinh.c,v 1.9 1995/05/12 04:57:37 jtc Exp $";
#endif

/* asinh(x)
 * Method :
 *      Based on
 *              asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
 *      we have
 *      asinh(x) := x  if  1+x*x=1,
 *               := sign(x)*(log(x)+ln2)) for large |x|, else
 *               := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
 *               := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
 */

#include <math.h>
#include <unixlib/math.h>
#include <unixlib/types.h>

static const double
  one = 1.00000000000000000000e+00,	/* 0x3FF00000, 0x00000000 */
  ln2 = 6.93147180559945286227e-01,	/* 0x3FE62E42, 0xFEFA39EF */
  huge = 1.00000000000000000000e+300;

double
asinh (double x)
{
  double t, w;
  __int32_t hx, ix;

  GET_HIGH_WORD (hx, x);
  ix = hx & 0x7fffffff;
  if (ix >= 0x7ff00000)
    return x + x;		/* x is inf or NaN */
  if (ix < 0x3e300000)
    {				/* |x|<2**-28 */
      if (huge + x > one)
	return x;		/* return x inexact except 0 */
    }
  if (ix > 0x41b00000)
    {				/* |x| > 2**28 */
      w = log (fabs (x)) + ln2;
    }
  else if (ix > 0x40000000)
    {				/* 2**28 > |x| > 2.0 */
      t = fabs (x);
      w = log (2.0 * t + one / (sqrt (x * x + one) + t));
    }
  else
    {				/* 2.0 > |x| > 2**-28 */
      t = x * x;
      w = log1p (fabs (x) + t / (one + sqrt (one + t)));
    }
  if (hx > 0)
    return w;
  else
    return -w;
}
