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/combit.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 gmp-6.3.0/mpz/combit.c

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

diff --git a/gmp-6.3.0/mpz/combit.c b/gmp-6.3.0/mpz/combit.c
new file mode 100644
index 0000000..0a29875
--- /dev/null
+++ b/gmp-6.3.0/mpz/combit.c
@@ -0,0 +1,103 @@
+/* mpz_combit -- complement a specified bit.
+
+Copyright 2002, 2003, 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"
+
+void
+mpz_combit (mpz_ptr d, mp_bitcnt_t bit_index)
+{
+  mp_size_t dsize = SIZ(d);
+  mp_ptr dp = PTR(d);
+
+  mp_size_t limb_index = bit_index / GMP_NUMB_BITS;
+  mp_limb_t bit = (CNST_LIMB (1) << (bit_index % GMP_NUMB_BITS));
+
+  /* Check for the most common case: Positive input, no realloc or
+     normalization needed. */
+  if (limb_index + 1 < dsize)
+    dp[limb_index] ^= bit;
+
+  /* Check for the hairy case. d < 0, and we have all zero bits to the
+     right of the bit to toggle. */
+  else if (limb_index < -dsize
+	   && (limb_index == 0 || mpn_zero_p (dp, limb_index))
+	   && (dp[limb_index] & (bit - 1)) == 0)
+    {
+      ASSERT (dsize < 0);
+      dsize = -dsize;
+
+      if (dp[limb_index] & bit)
+	{
+	  /* We toggle the least significant one bit. Corresponds to
+	     an add, with potential carry propagation, on the absolute
+	     value. */
+	  dp = MPZ_REALLOC (d, 1 + dsize);
+	  dp[dsize] = 0;
+	  MPN_INCR_U (dp + limb_index, 1 + dsize - limb_index, bit);
+	  SIZ(d) = - dsize - dp[dsize];
+	}
+      else
+	{
+	  /* We toggle a zero bit, subtract from the absolute value. */
+	  MPN_DECR_U (dp + limb_index, dsize - limb_index, bit);
+	  /* The absolute value shrinked by at most one bit. */
+	  dsize -= dp[dsize - 1] == 0;
+	  ASSERT (dsize > 0 && dp[dsize - 1] != 0);
+	  SIZ (d) = -dsize;
+	}
+    }
+  else
+    {
+      /* Simple case: Toggle the bit in the absolute value. */
+      dsize = ABS(dsize);
+      if (limb_index < dsize)
+	{
+	  mp_limb_t	 dlimb;
+	  dlimb = dp[limb_index] ^ bit;
+	  dp[limb_index] = dlimb;
+
+	  /* Can happen only when limb_index = dsize - 1. Avoid SIZ(d)
+	     bookkeeping in the common case. */
+	  if (UNLIKELY ((dlimb == 0) + limb_index == dsize)) /* dsize == limb_index + 1 */
+	    {
+	      /* high limb became zero, must normalize */
+	      MPN_NORMALIZE (dp, limb_index);
+	      SIZ (d) = SIZ (d) >= 0 ? limb_index : -limb_index;
+	    }
+	}
+      else
+	{
+	  dp = MPZ_REALLOC (d, limb_index + 1);
+	  MPN_ZERO(dp + dsize, limb_index - dsize);
+	  dp[limb_index++] = bit;
+	  SIZ(d) = SIZ(d) >= 0 ? limb_index : -limb_index;
+	}
+    }
+}
-- 
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