1 /* mpz_gcd_ui -- Calculate the greatest common divisior of two integers. 2 3 Copyright 1994, 1996, 1999, 2000, 2001, 2002, 2003, 2004 Free Software 4 Foundation, Inc. 5 6 This file is part of the GNU MP Library. 7 8 The GNU MP Library is free software; you can redistribute it and/or modify 9 it under the terms of the GNU Lesser General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or (at your 11 option) any later version. 12 13 The GNU MP Library is distributed in the hope that it will be useful, but 14 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 15 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 16 License for more details. 17 18 You should have received a copy of the GNU Lesser General Public License 19 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 20 21 #include <stdio.h> /* for NULL */ 22 #include "gmp.h" 23 #include "gmp-impl.h" 24 25 unsigned long int 26 mpz_gcd_ui (mpz_ptr w, mpz_srcptr u, unsigned long int v) 27 { 28 mp_size_t un; 29 mp_limb_t res; 30 31 #if BITS_PER_ULONG > GMP_NUMB_BITS /* avoid warnings about shift amount */ 32 if (v > GMP_NUMB_MAX) 33 { 34 mpz_t vz; 35 mp_limb_t vlimbs[2]; 36 vlimbs[0] = v & GMP_NUMB_MASK; 37 vlimbs[1] = v >> GMP_NUMB_BITS; 38 PTR(vz) = vlimbs; 39 SIZ(vz) = 2; 40 mpz_gcd (w, u, vz); 41 /* because v!=0 we will have w<=v hence fitting a ulong */ 42 ASSERT (mpz_fits_ulong_p (w)); 43 return mpz_get_ui (w); 44 } 45 #endif 46 47 un = ABSIZ(u); 48 49 if (un == 0) 50 res = v; 51 else if (v == 0) 52 { 53 if (w != NULL) 54 { 55 if (u != w) 56 { 57 MPZ_REALLOC (w, un); 58 MPN_COPY (PTR(w), PTR(u), un); 59 } 60 SIZ(w) = un; 61 } 62 /* Return u if it fits a ulong, otherwise 0. */ 63 res = PTR(u)[0]; 64 return (un == 1 && res <= ULONG_MAX ? res : 0); 65 } 66 else 67 res = mpn_gcd_1 (PTR(u), un, (mp_limb_t) v); 68 69 if (w != NULL) 70 { 71 PTR(w)[0] = res; 72 SIZ(w) = res != 0; 73 } 74 return res; 75 } 76