74 lines
1.9 KiB
C
74 lines
1.9 KiB
C
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/* mpn_gcd_1 --
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Copyright (C) 1994, 1996 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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/* Does not work for U == 0 or V == 0. It would be tough to make it work for
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V == 0 since gcd(x,0) = x, and U does not generally fit in an mp_limb_t. */
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mp_limb_t
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mpn_gcd_1 (up, size, vlimb)
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mp_srcptr up;
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mp_size_t size;
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mp_limb_t vlimb;
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{
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mp_limb_t ulimb;
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unsigned long int u_low_zero_bits, v_low_zero_bits;
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if (size > 1)
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{
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ulimb = mpn_mod_1 (up, size, vlimb);
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if (ulimb == 0)
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return vlimb;
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}
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else
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ulimb = up[0];
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/* Need to eliminate low zero bits. */
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count_trailing_zeros (u_low_zero_bits, ulimb);
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ulimb >>= u_low_zero_bits;
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count_trailing_zeros (v_low_zero_bits, vlimb);
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vlimb >>= v_low_zero_bits;
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while (ulimb != vlimb)
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{
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if (ulimb > vlimb)
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{
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ulimb -= vlimb;
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do
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ulimb >>= 1;
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while ((ulimb & 1) == 0);
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}
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else /* vlimb > ulimb. */
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{
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vlimb -= ulimb;
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do
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vlimb >>= 1;
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while ((vlimb & 1) == 0);
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}
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}
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return ulimb << MIN (u_low_zero_bits, v_low_zero_bits);
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}
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