gcd.c
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上传日期:2013-07-19
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- /* ***** BEGIN LICENSE BLOCK *****
- * Version: RCSL 1.0/RPSL 1.0
- *
- * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved.
- *
- * The contents of this file, and the files included with this file, are
- * subject to the current version of the RealNetworks Public Source License
- * Version 1.0 (the "RPSL") available at
- * http://www.helixcommunity.org/content/rpsl unless you have licensed
- * the file under the RealNetworks Community Source License Version 1.0
- * (the "RCSL") available at http://www.helixcommunity.org/content/rcsl,
- * in which case the RCSL will apply. You may also obtain the license terms
- * directly from RealNetworks. You may not use this file except in
- * compliance with the RPSL or, if you have a valid RCSL with RealNetworks
- * applicable to this file, the RCSL. Please see the applicable RPSL or
- * RCSL for the rights, obligations and limitations governing use of the
- * contents of the file.
- *
- * This file is part of the Helix DNA Technology. RealNetworks is the
- * developer of the Original Code and owns the copyrights in the portions
- * it created.
- *
- * This file, and the files included with this file, is distributed and made
- * available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
- * EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES,
- * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS
- * FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
- *
- * Technology Compatibility Kit Test Suite(s) Location:
- * http://www.helixcommunity.org/content/tck
- *
- * Contributor(s):
- *
- * ***** END LICENSE BLOCK ***** */
- #include "gcd.h"
- /* calculate the gcd of the input arguments. Taken from Knuth, TAOCP Vol. 2 */
- signed long gcd(signed long u, signed long v)
- {
- int k = 0 ;
- signed long t ;
- while (!((u | v) & 1)) /* while both u and v are even */
- {
- u >>= 1 ; v >>= 1 ; k++ ;
- }
- t = (u & 1) ? -v : u ;
- do {
- /* Halve t until it is odd */
- while (!(t & 1)) t >>= 1 ;
- /* Replace the larger of u and v by |t|, except perhaps
- during the first time this step is performed */
- if (t > 0) u = t ;
- else v = -t ;
- t = u-v ;
- }
- while (t!=0) ;
- /* return u * 2^k */
- return (u << k) ;
- }