auto import from //depot/cupcake/@135843

1 files changed, 54 insertions, 0 deletions

diff --git a/lib/next_prime.c b/lib/next_prime.c
new file mode 100644
index 00000000..5d608046
--- /dev/null
+++ b/lib/next_prime.c
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+/* Determine prime number.
+   Copyright (C) 2000, 2002 Free Software Foundation, Inc.
+   Written by Ulrich Drepper <drepper@redhat.com>, 2000.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, version 2.
+
+   This program 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 a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software Foundation,
+   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+#include <stddef.h>
+
+
+/* Test whether CANDIDATE is a prime.  */
+static int
+is_prime (size_t candidate)
+{
+  /* No even number and none less than 10 will be passed here.  */
+  size_t divn = 3;
+  size_t sq = divn * divn;
+
+  while (sq < candidate && candidate % divn != 0)
+    {
+      size_t old_sq = sq;
+      ++divn;
+      sq += 4 * divn;
+      if (sq < old_sq)
+	return 1;
+      ++divn;
+    }
+
+  return candidate % divn != 0;
+}
+
+
+/* We need primes for the table size.  */
+size_t
+next_prime (size_t seed)
+{
+  /* Make it definitely odd.  */
+  seed |= 1;
+
+  while (!is_prime (seed))
+    seed += 2;
+
+  return seed;
+}