From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001
From: Duncan Wilkie <antigravityd@gmail.com>
Date: Sat, 18 Nov 2023 06:11:09 -0600
Subject: Initial commit.

---
 gmp-6.3.0/mpz/scan1.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 123 insertions(+)
 create mode 100644 gmp-6.3.0/mpz/scan1.c

(limited to 'gmp-6.3.0/mpz/scan1.c')

diff --git a/gmp-6.3.0/mpz/scan1.c b/gmp-6.3.0/mpz/scan1.c
new file mode 100644
index 0000000..d096147
--- /dev/null
+++ b/gmp-6.3.0/mpz/scan1.c
@@ -0,0 +1,123 @@
+/* mpz_scan1 -- search for a 1 bit.
+
+Copyright 2000-2002, 2004, 2012, 2015 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"
+
+
+/* mpn_scan0 can't be used for the inverted u<0 search since there might not
+   be a 0 bit before the end of the data.  mpn_scan1 could be used under u>0
+   (except when in the high limb), but usually the search won't go very far
+   so it seems reasonable to inline that code.  */
+
+mp_bitcnt_t
+mpz_scan1 (mpz_srcptr u, mp_bitcnt_t starting_bit) __GMP_NOTHROW
+{
+  mp_srcptr      u_ptr = PTR(u);
+  mp_size_t      size = SIZ(u);
+  mp_size_t      abs_size = ABS(size);
+  mp_srcptr      u_end = u_ptr + abs_size - 1;
+  mp_size_t      starting_limb = starting_bit / GMP_NUMB_BITS;
+  mp_srcptr      p = u_ptr + starting_limb;
+  mp_limb_t      limb;
+  int            cnt;
+
+  /* Past the end there's no 1 bits for u>=0, or an immediate 1 bit for u<0.
+     Notice this test picks up any u==0 too. */
+  if (starting_limb >= abs_size)
+    return (size >= 0 ? ~(mp_bitcnt_t) 0 : starting_bit);
+
+  /* This is an important case, where sign is not relevant! */
+  if (starting_bit == 0)
+    goto short_cut;
+
+  limb = *p;
+
+  if (size >= 0)
+    {
+      /* Mask to 0 all bits before starting_bit, thus ignoring them. */
+      limb &= (MP_LIMB_T_MAX << (starting_bit % GMP_NUMB_BITS));
+
+      if (limb == 0)
+	{
+	  /* If it's the high limb which is zero after masking, then there's
+	     no 1 bits after starting_bit.  */
+	  if (p == u_end)
+	    return ~(mp_bitcnt_t) 0;
+
+	  /* Otherwise search further for a non-zero limb.  The high limb is
+	     non-zero, if nothing else.  */
+	search_nonzero:
+	  do
+	    {
+	      ASSERT (p != u_end);
+	      p++;
+	    short_cut:
+	      limb = *p;
+	    }
+	  while (limb == 0);
+	}
+    }
+  else
+    {
+      /* If there's a non-zero limb before ours then we're in the ones
+	 complement region.  */
+      if (starting_limb == 0 || mpn_zero_p (u_ptr, starting_limb)) {
+	if (limb == 0)
+	  /* Seeking for the first non-zero bit, it is the same for u and -u. */
+	  goto search_nonzero;
+
+	/* Adjust so ~limb implied by searching for 0 bit becomes -limb.  */
+	limb--;
+      }
+
+      /* Now seeking a 0 bit. */
+
+      /* Mask to 1 all bits before starting_bit, thus ignoring them. */
+      limb |= (CNST_LIMB(1) << (starting_bit % GMP_NUMB_BITS)) - 1;
+
+      /* Search for a limb which is not all ones.  If the end is reached
+	 then the zero immediately past the end is the result.  */
+      while (limb == GMP_NUMB_MAX)
+	{
+	  if (p == u_end)
+	    return (mp_bitcnt_t) abs_size * GMP_NUMB_BITS;
+	  p++;
+	  limb = *p;
+	}
+
+      /* Now seeking low 1 bit. */
+      limb = ~limb;
+    }
+
+  ASSERT (limb != 0);
+  count_trailing_zeros (cnt, limb);
+  return (mp_bitcnt_t) (p - u_ptr) * GMP_NUMB_BITS + cnt;
+}
-- 
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