Add libgmp 6.2.0 to third_party
Don't build it yet. That will come in the next review.
Change-Id: Idf3266558165e5ab45f4a41c98cc8c838c8244d5
diff --git a/third_party/gmp/mpz/hamdist.c b/third_party/gmp/mpz/hamdist.c
new file mode 100644
index 0000000..1dfb7b8
--- /dev/null
+++ b/third_party/gmp/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;
+ }
+}