diff options
Diffstat (limited to 'contrib/libgmp/mpn/generic/gcd_1.c')
-rw-r--r-- | contrib/libgmp/mpn/generic/gcd_1.c | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/contrib/libgmp/mpn/generic/gcd_1.c b/contrib/libgmp/mpn/generic/gcd_1.c new file mode 100644 index 0000000..ebcdfb5 --- /dev/null +++ b/contrib/libgmp/mpn/generic/gcd_1.c @@ -0,0 +1,73 @@ +/* mpn_gcd_1 -- + +Copyright (C) 1994, 1996 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 Library General Public License as published by +the Free Software Foundation; either version 2 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 Library General Public +License for more details. + +You should have received a copy of the GNU Library General Public License +along with the GNU MP Library; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include "gmp.h" +#include "gmp-impl.h" +#include "longlong.h" + +/* Does not work for U == 0 or V == 0. It would be tough to make it work for + V == 0 since gcd(x,0) = x, and U does not generally fit in an mp_limb_t. */ + +mp_limb_t +mpn_gcd_1 (up, size, vlimb) + mp_srcptr up; + mp_size_t size; + mp_limb_t vlimb; +{ + mp_limb_t ulimb; + unsigned long int u_low_zero_bits, v_low_zero_bits; + + if (size > 1) + { + ulimb = mpn_mod_1 (up, size, vlimb); + if (ulimb == 0) + return vlimb; + } + else + ulimb = up[0]; + + /* Need to eliminate low zero bits. */ + count_trailing_zeros (u_low_zero_bits, ulimb); + ulimb >>= u_low_zero_bits; + + count_trailing_zeros (v_low_zero_bits, vlimb); + vlimb >>= v_low_zero_bits; + + while (ulimb != vlimb) + { + if (ulimb > vlimb) + { + ulimb -= vlimb; + do + ulimb >>= 1; + while ((ulimb & 1) == 0); + } + else /* vlimb > ulimb. */ + { + vlimb -= ulimb; + do + vlimb >>= 1; + while ((vlimb & 1) == 0); + } + } + + return ulimb << MIN (u_low_zero_bits, v_low_zero_bits); +} |