text: /* mpz_gcd_ui -- Calculate the greatest common divisor of two integers.
  
  Copyright 1994, 1996, 1999, 2000, 2001, 2002, 2003, 2004 Free Software
  Foundation, Inc.
  
  This file is part of the GNU MP Library.
  
  The GNU MP 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 3 of the License, or (at your
  option) any later version.
  
  The GNU MP 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 MP Library.  If not, see http://www.gnu.org/licenses/.  */
  
  #include <stdio.h> /* for NULL */
  #include "gmp.h"
  #include "gmp-impl.h"
  
  unsigned long int
  mpz_gcd_ui (mpz_ptr w, mpz_srcptr u, unsigned long int v)
  {
    mp_size_t un;
    mp_limb_t res;
  
  #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
    if (v > GMP_NUMB_MAX)
      {
        mpz_t vz;
        mp_limb_t vlimbs[2];
        vlimbs[0] = v & GMP_NUMB_MASK;
        vlimbs[1] = v >> GMP_NUMB_BITS;
        PTR(vz) = vlimbs;
        SIZ(vz) = 2;
        mpz_gcd (w, u, vz);
        /* because v!=0 we will have w<=v hence fitting a ulong */
        ASSERT (mpz_fits_ulong_p (w));
        return mpz_get_ui (w);
      }
  #endif
  
    un = ABSIZ(u);
  
    if (un == 0)
      res = v;
    else if (v == 0)
      {
        if (w != NULL)
  	{
  	  if (u != w)
  	    {
  	      MPZ_REALLOC (w, un);
  	      MPN_COPY (PTR(w), PTR(u), un);
  	    }
  	  SIZ(w) = un;
  	}
        /* Return u if it fits a ulong, otherwise 0. */
        res = PTR(u)[0];
        return (un == 1 && res <= ULONG_MAX ? res : 0);
      }
    else
      res = mpn_gcd_1 (PTR(u), un, (mp_limb_t) v);
  
    if (w != NULL)
      {
        PTR(w)[0] = res;
        SIZ(w) = res != 0;
      }
    return res;
  }
  