/* Compute complex natural logarithm.

   Copyright (C) 1997-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <complex.h>

#include <math.h>

#include <math_private.h>

#include <math-underflow.h>

#include <float.h>

CFLOAT

M_DECL_FUNC (__clog) (CFLOAT x)

{

  CFLOAT result;

  int rcls = fpclassify (__real__ x);

  int icls = fpclassify (__imag__ x);

  if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))

    {

      /* Real and imaginary part are 0.0.  */

      __imag__ result = signbit (__real__ x) ? (FLOAT) M_MLIT (M_PI) : 0;

      __imag__ result = M_COPYSIGN (__imag__ result, __imag__ x);

      /* Yes, the following line raises an exception.  */

      __real__ result = -1 / M_FABS (__real__ x);

    }

  else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))

    {

      /* Neither real nor imaginary part is NaN.  */

      FLOAT absx = M_FABS (__real__ x), absy = M_FABS (__imag__ x);

      int scale = 0;

      if (absx < absy)

	{

	  FLOAT t = absx;

	  absx = absy;

	  absy = t;

	}

      if (absx > M_MAX / 2)

	{

	  scale = -1;

	  absx = M_SCALBN (absx, scale);

	  absy = (absy >= M_MIN * 2 ? M_SCALBN (absy, scale) : 0);

	}

      else if (absx < M_MIN && absy < M_MIN)

	{

	  scale = M_MANT_DIG;

	  absx = M_SCALBN (absx, scale);

	  absy = M_SCALBN (absy, scale);

	}

      if (absx == 1 && scale == 0)

	{

	  __real__ result = M_LOG1P (absy * absy) / 2;

	  math_check_force_underflow_nonneg (__real__ result);

	}

      else if (absx > 1 && absx < 2 && absy < 1 && scale == 0)

	{

	  FLOAT d2m1 = (absx - 1) * (absx + 1);

	  if (absy >= M_EPSILON)

	    d2m1 += absy * absy;

	  __real__ result = M_LOG1P (d2m1) / 2;

	}

      else if (absx < 1

	       && absx >= M_LIT (0.5)

	       && absy < M_EPSILON / 2

	       && scale == 0)

	{

	  FLOAT d2m1 = (absx - 1) * (absx + 1);

	  __real__ result = M_LOG1P (d2m1) / 2;

	}

      else if (absx < 1

	       && absx >= M_LIT (0.5)

	       && scale == 0

	       && absx * absx + absy * absy >= M_LIT (0.5))

	{

	  FLOAT d2m1 = M_SUF (__x2y2m1) (absx, absy);

	  __real__ result = M_LOG1P (d2m1) / 2;

	}

      else

	{

	  FLOAT d = M_HYPOT (absx, absy);

	  __real__ result = M_LOG (d) - scale * (FLOAT) M_MLIT (M_LN2);

	}

      __imag__ result = M_ATAN2 (__imag__ x, __real__ x);

    }

  else

    {

      __imag__ result = M_NAN;

      if (rcls == FP_INFINITE || icls == FP_INFINITE)

	/* Real or imaginary part is infinite.  */

	__real__ result = M_HUGE_VAL;

      else

	__real__ result = M_NAN;

    }

  return result;

}

declare_mgen_alias (__clog, clog)