From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001 From: Duncan Wilkie Date: Sat, 18 Nov 2023 06:11:09 -0600 Subject: Initial commit. --- gmp-6.3.0/mpz/cong_2exp.c | 149 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 149 insertions(+) create mode 100644 gmp-6.3.0/mpz/cong_2exp.c (limited to 'gmp-6.3.0/mpz/cong_2exp.c') diff --git a/gmp-6.3.0/mpz/cong_2exp.c b/gmp-6.3.0/mpz/cong_2exp.c new file mode 100644 index 0000000..9de9645 --- /dev/null +++ b/gmp-6.3.0/mpz/cong_2exp.c @@ -0,0 +1,149 @@ +/* mpz_congruent_2exp_p -- test congruence of mpz mod 2^n. + +Copyright 2001, 2002, 2013 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" + + +int +mpz_congruent_2exp_p (mpz_srcptr a, mpz_srcptr c, mp_bitcnt_t d) __GMP_NOTHROW +{ + mp_size_t i, dlimbs; + unsigned dbits; + mp_ptr ap, cp; + mp_limb_t dmask, alimb, climb, sum; + mp_size_t as, cs, asize, csize; + + as = SIZ(a); + asize = ABS(as); + + cs = SIZ(c); + csize = ABS(cs); + + if (asize < csize) + { + MPZ_SRCPTR_SWAP (a, c); + MP_SIZE_T_SWAP (asize, csize); + } + + dlimbs = d / GMP_NUMB_BITS; + dbits = d % GMP_NUMB_BITS; + dmask = (CNST_LIMB(1) << dbits) - 1; + + ap = PTR(a); + cp = PTR(c); + + if (csize == 0) + goto a_zeros; + + if ((cs ^ as) >= 0) + { + /* same signs, direct comparison */ + + /* a==c for limbs in common */ + if (mpn_cmp (ap, cp, MIN (csize, dlimbs)) != 0) + return 0; + + /* if that's all of dlimbs, then a==c for remaining bits */ + if (csize > dlimbs) + return ((ap[dlimbs]-cp[dlimbs]) & dmask) == 0; + + a_zeros: + /* a remains, need all zero bits */ + + /* if d covers all of a and c, then must be exactly equal */ + if (asize <= dlimbs) + return asize == csize; + + /* whole limbs zero */ + for (i = csize; i < dlimbs; i++) + if (ap[i] != 0) + return 0; + + /* partial limb zero */ + return (ap[dlimbs] & dmask) == 0; + } + else + { + /* different signs, negated comparison */ + + /* common low zero limbs, stopping at first non-zeros, which must + match twos complement */ + i = 0; + do + { + ASSERT (i < csize); /* always have a non-zero limb on c */ + alimb = ap[i]; + climb = cp[i]; + sum = (alimb + climb) & GMP_NUMB_MASK; + + if (i >= dlimbs) + return (sum & dmask) == 0; + ++i; + + /* require both zero, or first non-zeros as twos-complements */ + if (sum != 0) + return 0; + } while (alimb == 0); + + /* further limbs matching as ones-complement */ + for (; i < csize; ++i) + { + alimb = ap[i]; + climb = cp[i]; + sum = alimb ^ climb ^ GMP_NUMB_MASK; + + if (i >= dlimbs) + return (sum & dmask) == 0; + + if (sum != 0) + return 0; + } + + /* no more c, so require all 1 bits in a */ + + if (asize < dlimbs) + return 0; /* not enough a */ + + /* whole limbs */ + for ( ; i < dlimbs; i++) + if (ap[i] != GMP_NUMB_MAX) + return 0; + + /* if only whole limbs, no further fetches from a */ + if (dbits == 0) + return 1; + + /* need enough a */ + if (asize == dlimbs) + return 0; + + return ((ap[dlimbs]+1) & dmask) == 0; + } +} -- cgit v1.2.3