1 files changed, 90 insertions, 0 deletions
diff --git a/db2/common/db_shash.c b/db2/common/db_shash.c
new file mode 100644
index 0000000000..988de8a994
--- /dev/null
+++ b/db2/common/db_shash.c
@@ -0,0 +1,90 @@
+/*-
+ * See the file LICENSE for redistribution information.
+ *
+ * Copyright (c) 1996, 1997
+ *	Sleepycat Software.  All rights reserved.
+ */
+
+#include "config.h"
+
+#ifndef lint
+static const char sccsid[] = "@(#)db_shash.c	10.3 (Sleepycat) 6/21/97";
+#endif /* not lint */
+
+#ifndef NO_SYSTEM_INCLUDES
+#include <sys/types.h>
+#endif
+
+#include "db_int.h"
+#include "shqueue.h"
+#include "common_ext.h"
+
+/* Powers-of-2 and close-by prime number pairs. */
+static const struct {
+	int	power;
+	int	prime;
+} list[] = {
+	{  64,	  67},
+	{ 128,	 131},
+	{ 256,	 257},
+	{ 512,	 521},
+	{1024,	1031},
+	{2048,	2053},
+	{4096,	4099},
+	{8192,	8191},
+	{0,	   0}
+};
+
+/*
+ * __db_tablesize --
+ *	Choose a size for the hash table.
+ *
+ * PUBLIC: int __db_tablesize __P((int));
+ */
+int
+__db_tablesize(n_buckets)
+	int n_buckets;
+{
+	int i;
+
+	/*
+	 * We try to be clever about how big we make the hash tables.  Pick
+	 * a prime number close to the "suggested" number of elements that
+	 * will be in the hash table.  We shoot for minimum collisions (i.e.
+	 * one element in each bucket).  We use 64 as the minimum table size.
+	 *
+	 * Ref: Sedgewick, Algorithms in C, "Hash Functions"
+	 */
+	if (n_buckets < 64)
+		n_buckets = 64;
+
+	for (i = 0;; ++i) {
+		if (list[i].power == 0) {
+			--i;
+			break;
+		}
+		if (list[i].power >= n_buckets)
+			break;
+	}
+	return (list[i].prime);
+}
+
+/*
+ * __db_hashinit --
+ *	Initialize a hash table that resides in shared memory.
+ *
+ * PUBLIC: void __db_hashinit __P((void *, int));
+ */
+void
+__db_hashinit(begin, nelements)
+	void *begin;
+	int nelements;
+{
+	int i;
+	SH_TAILQ_HEAD(hash_head) *headp;
+
+	headp = (struct hash_head *)begin;
+
+	for (i = 0; i < nelements; i++, headp++)
+		SH_TAILQ_INIT(headp);
+}