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Diffstat (limited to 'gmp-6.3.0/mpz/cong_ui.c')
-rw-r--r--gmp-6.3.0/mpz/cong_ui.c115
1 files changed, 115 insertions, 0 deletions
diff --git a/gmp-6.3.0/mpz/cong_ui.c b/gmp-6.3.0/mpz/cong_ui.c
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+++ b/gmp-6.3.0/mpz/cong_ui.c
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+/* mpz_congruent_ui_p -- test congruence of mpz and ulong.
+
+Copyright 2000-2002, 2012 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 either:
+
+ * the GNU Lesser General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your
+ option) any later version.
+
+or
+
+ * the GNU General Public License as published by the Free Software
+ Foundation; either version 2 of the License, or (at your option) any
+ later version.
+
+or both in parallel, as here.
+
+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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library. If not,
+see https://www.gnu.org/licenses/. */
+
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* There's some explicit checks for c<d since it seems reasonably likely an
+ application might use that in a test.
+
+ Hopefully the compiler can generate something good for r==(c%d), though
+ if modexact is being used exclusively then that's not reached. */
+
+int
+mpz_congruent_ui_p (mpz_srcptr a, unsigned long cu, unsigned long du)
+{
+ mp_srcptr ap;
+ mp_size_t asize;
+ mp_limb_t c, d, r;
+
+ if (UNLIKELY (du == 0))
+ return (mpz_cmp_ui (a, cu) == 0);
+
+ asize = SIZ(a);
+ if (asize == 0)
+ {
+ if (cu < du)
+ return cu == 0;
+ else
+ return (cu % du) == 0;
+ }
+
+ /* For nails don't try to be clever if c or d is bigger than a limb, just
+ fake up some mpz_t's and go to the main mpz_congruent_p. */
+ if (du > GMP_NUMB_MAX || cu > GMP_NUMB_MAX)
+ {
+ mp_limb_t climbs[2], dlimbs[2];
+ mpz_t cz, dz;
+
+ ALLOC(cz) = 2;
+ PTR(cz) = climbs;
+ ALLOC(dz) = 2;
+ PTR(dz) = dlimbs;
+
+ mpz_set_ui (cz, cu);
+ mpz_set_ui (dz, du);
+ return mpz_congruent_p (a, cz, dz);
+ }
+
+ /* NEG_MOD works on limbs, so convert ulong to limb */
+ c = cu;
+ d = du;
+
+ if (asize < 0)
+ {
+ asize = -asize;
+ NEG_MOD (c, c, d);
+ }
+
+ ap = PTR (a);
+
+ if (ABOVE_THRESHOLD (asize, BMOD_1_TO_MOD_1_THRESHOLD))
+ {
+ r = mpn_mod_1 (ap, asize, d);
+ if (c < d)
+ return r == c;
+ else
+ return r == (c % d);
+ }
+
+ if ((d & 1) == 0)
+ {
+ /* Strip low zero bits to get odd d required by modexact. If
+ d==e*2^n then a==c mod d if and only if both a==c mod 2^n
+ and a==c mod e. */
+
+ unsigned twos;
+
+ if ((ap[0]-c) & LOW_ZEROS_MASK (d))
+ return 0;
+
+ count_trailing_zeros (twos, d);
+ d >>= twos;
+ }
+
+ r = mpn_modexact_1c_odd (ap, asize, d, c);
+ return r == 0 || r == d;
+}