github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpz/gcd_ui.c (about)

     1  /* mpz_gcd_ui -- Calculate the greatest common divisor of two integers.
     2  
     3  Copyright 1994, 1996, 1999-2004 Free Software Foundation, Inc.
     4  
     5  This file is part of the GNU MP Library.
     6  
     7  The GNU MP Library is free software; you can redistribute it and/or modify
     8  it under the terms of either:
     9  
    10    * the GNU Lesser General Public License as published by the Free
    11      Software Foundation; either version 3 of the License, or (at your
    12      option) any later version.
    13  
    14  or
    15  
    16    * the GNU General Public License as published by the Free Software
    17      Foundation; either version 2 of the License, or (at your option) any
    18      later version.
    19  
    20  or both in parallel, as here.
    21  
    22  The GNU MP Library is distributed in the hope that it will be useful, but
    23  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    24  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    25  for more details.
    26  
    27  You should have received copies of the GNU General Public License and the
    28  GNU Lesser General Public License along with the GNU MP Library.  If not,
    29  see https://www.gnu.org/licenses/.  */
    30  
    31  #include <stdio.h> /* for NULL */
    32  #include "gmp.h"
    33  #include "gmp-impl.h"
    34  
    35  unsigned long int
    36  mpz_gcd_ui (mpz_ptr w, mpz_srcptr u, unsigned long int v)
    37  {
    38    mp_size_t un;
    39    mp_limb_t res;
    40  
    41  #if BITS_PER_ULONG > GMP_NUMB_BITS  /* avoid warnings about shift amount */
    42    if (v > GMP_NUMB_MAX)
    43      {
    44        mpz_t vz;
    45        mp_limb_t vlimbs[2];
    46        vlimbs[0] = v & GMP_NUMB_MASK;
    47        vlimbs[1] = v >> GMP_NUMB_BITS;
    48        PTR(vz) = vlimbs;
    49        SIZ(vz) = 2;
    50        mpz_gcd (w, u, vz);
    51        /* because v!=0 we will have w<=v hence fitting a ulong */
    52        ASSERT (mpz_fits_ulong_p (w));
    53        return mpz_get_ui (w);
    54      }
    55  #endif
    56  
    57    un = ABSIZ(u);
    58  
    59    if (un == 0)
    60      res = v;
    61    else if (v == 0)
    62      {
    63        if (w != NULL)
    64  	{
    65  	  if (u != w)
    66  	    {
    67  	      MPZ_REALLOC (w, un);
    68  	      MPN_COPY (PTR(w), PTR(u), un);
    69  	    }
    70  	  SIZ(w) = un;
    71  	}
    72        /* Return u if it fits a ulong, otherwise 0. */
    73        res = PTR(u)[0];
    74        return (un == 1 && res <= ULONG_MAX ? res : 0);
    75      }
    76    else
    77      res = mpn_gcd_1 (PTR(u), un, (mp_limb_t) v);
    78  
    79    if (w != NULL)
    80      {
    81        PTR(w)[0] = res;
    82        SIZ(w) = res != 0;
    83      }
    84    return res;
    85  }