1: /* Copyright (C) 2005, 2006 Free Software Foundation, Inc.
    2:    This file is part of the GNU C Library.
    3:    Contributed by Richard Henderson <rth@redhat.com>, 2005.
    4: 
    5:    The GNU C Library is free software; you can redistribute it and/or
    6:    modify it under the terms of the GNU Lesser General Public
    7:    License as published by the Free Software Foundation; either
    8:    version 2.1 of the License, or (at your option) any later version.
    9: 
   10:    The GNU C Library is distributed in the hope that it will be useful,
   11:    but WITHOUT ANY WARRANTY; without even the implied warranty of
   12:    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   13:    Lesser General Public License for more details.
   14: 
   15:    You should have received a copy of the GNU Lesser General Public
   16:    License along with the GNU C Library; if not, write to the Free
   17:    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   18:    02111-1307 USA.  */
   19: 
   20: #include <stdbool.h>
   21: #include <math.h>
   22: #include <complex.h>
   23: 
   24: attribute_hidden
   25: long double _Complex
   26: __divtc3 (long double a, long double b, long double c, long double d)
   27: {
   28:   long double denom, ratio, x, y;
   29: 
   30:   /* ??? We can get better behavior from logarithmic scaling instead of
   31:      the division.  But that would mean starting to link libgcc against
   32:      libm.  We could implement something akin to ldexp/frexp as gcc builtins
   33:      fairly easily...  */
   34:   if (fabsl (c) < fabsl (d))
   35:     {
   36:       ratio = c / d;
   37:       denom = (c * ratio) + d;
   38:       x = ((a * ratio) + b) / denom;
   39:       y = ((b * ratio) - a) / denom;
   40:     }
   41:   else
   42:     {
   43:       ratio = d / c;
   44:       denom = (d * ratio) + c;
   45:       x = ((b * ratio) + a) / denom;
   46:       y = (b - (a * ratio)) / denom;
   47:     }
   48: 
   49:   /* Recover infinities and zeros that computed as NaN+iNaN; the only cases
   50:      are nonzero/zero, infinite/finite, and finite/infinite.  */
   51:   if (isnan (x) && isnan (y))
   52:     {
   53:       if (denom == 0.0 && (!isnan (a) || !isnan (b)))
   54:         {
   55:           x = __copysignl (INFINITY, c) * a;
   56:           y = __copysignl (INFINITY, c) * b;
   57:         }
   58:       else if ((isinf (a) || isinf (b)) && isfinite (c) && isfinite (d))
   59:         {
   60:           a = __copysignl (isinf (a) ? 1 : 0, a);
   61:           b = __copysignl (isinf (b) ? 1 : 0, b);
   62:           x = INFINITY * (a * c + b * d);
   63:           y = INFINITY * (b * c - a * d);
   64:         }
   65:       else if ((isinf (c) || isinf (d)) && isfinite (a) && isfinite (b))
   66:         {
   67:           c = __copysignl (isinf (c) ? 1 : 0, c);
   68:           d = __copysignl (isinf (d) ? 1 : 0, d);
   69:           x = 0.0 * (a * c + b * d);
   70:           y = 0.0 * (b * c - a * d);
   71:         }
   72:     }
   73: 
   74:   return x + I * y;
   75: }