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/hamdist.c | 174 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 174 insertions(+) create mode 100644 gmp-6.3.0/mpz/hamdist.c (limited to 'gmp-6.3.0/mpz/hamdist.c') diff --git a/gmp-6.3.0/mpz/hamdist.c b/gmp-6.3.0/mpz/hamdist.c new file mode 100644 index 0000000..1dfb7b8 --- /dev/null +++ b/gmp-6.3.0/mpz/hamdist.c @@ -0,0 +1,174 @@ +/* mpz_hamdist -- calculate hamming distance. + +Copyright 1994, 1996, 2001, 2002, 2009-2011 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" + + +mp_bitcnt_t +mpz_hamdist (mpz_srcptr u, mpz_srcptr v) __GMP_NOTHROW +{ + mp_srcptr up, vp; + mp_size_t usize, vsize; + mp_bitcnt_t count; + + usize = SIZ(u); + vsize = SIZ(v); + + up = PTR(u); + vp = PTR(v); + + if (usize >= 0) + { + if (vsize < 0) + return ~ (mp_bitcnt_t) 0; + + /* positive/positive */ + + if (usize < vsize) + MPN_SRCPTR_SWAP (up,usize, vp,vsize); + + count = 0; + if (vsize != 0) + count = mpn_hamdist (up, vp, vsize); + + usize -= vsize; + if (usize != 0) + count += mpn_popcount (up + vsize, usize); + + return count; + } + else + { + mp_limb_t ulimb, vlimb; + mp_size_t old_vsize, step; + + if (vsize >= 0) + return ~ (mp_bitcnt_t) 0; + + /* negative/negative */ + + usize = -usize; + vsize = -vsize; + + /* skip common low zeros */ + for (;;) + { + ASSERT (usize > 0); + ASSERT (vsize > 0); + + usize--; + vsize--; + + ulimb = *up++; + vlimb = *vp++; + + if (ulimb != 0) + break; + + if (vlimb != 0) + { + MPN_SRCPTR_SWAP (up,usize, vp,vsize); + ulimb = vlimb; + vlimb = 0; + break; + } + } + + /* twos complement first non-zero limbs (ulimb is non-zero, but vlimb + might be zero) */ + ulimb = -ulimb; + vlimb = -vlimb; + popc_limb (count, (ulimb ^ vlimb) & GMP_NUMB_MASK); + + if (vlimb == 0) + { + mp_bitcnt_t twoscount; + + /* first non-zero of v */ + old_vsize = vsize; + do + { + ASSERT (vsize > 0); + vsize--; + vlimb = *vp++; + } + while (vlimb == 0); + + /* part of u corresponding to skipped v zeros */ + step = old_vsize - vsize - 1; + count += step * GMP_NUMB_BITS; + step = MIN (step, usize); + if (step != 0) + { + count -= mpn_popcount (up, step); + usize -= step; + up += step; + } + + /* First non-zero vlimb as twos complement, xor with ones + complement ulimb. Note -v^(~0^u) == (v-1)^u. */ + vlimb--; + if (usize != 0) + { + usize--; + vlimb ^= *up++; + } + popc_limb (twoscount, vlimb); + count += twoscount; + } + + /* Overlapping part of u and v, if any. Ones complement both, so just + plain hamdist. */ + step = MIN (usize, vsize); + if (step != 0) + { + count += mpn_hamdist (up, vp, step); + usize -= step; + vsize -= step; + up += step; + vp += step; + } + + /* Remaining high part of u or v, if any, ones complement but xor + against all ones in the other, so plain popcount. */ + if (usize != 0) + { + remaining: + count += mpn_popcount (up, usize); + } + else if (vsize != 0) + { + up = vp; + usize = vsize; + goto remaining; + } + return count; + } +} -- cgit v1.2.3