From 369233927c6fc7f398d6ff4ea14ac8d648e19eae Mon Sep 17 00:00:00 2001
From: Wayne Davison <wayned@samba.org>
Date: Mon, 3 Sep 2007 04:46:57 +0000
Subject: [PATCH] The hashtable routines from hlink.c modified to have more
 generic names, to support 2 sizes of key (32 and 64 bits), and to have a
 non-allocating option for the find routine (returning NULL for no match).

---
 hashtable.c | 145 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 145 insertions(+)
 create mode 100644 hashtable.c

diff --git a/hashtable.c b/hashtable.c
new file mode 100644
index 00000000..d1be1b8a
--- /dev/null
+++ b/hashtable.c
@@ -0,0 +1,145 @@
+/*
+ * Routines to provide a memory-efficient hashtable.
+ *
+ * Copyright (C) 2007 Wayne Davison
+ *
+ * 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; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * 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, visit the http://fsf.org website.
+ */
+
+#include "rsync.h"
+
+#define HASH_LOAD_LIMIT(size) ((size)*3/4)
+
+struct hashtable *hashtable_create(int size, int key64)
+{
+	struct hashtable *tbl;
+	int node_size = key64 ? sizeof (struct ht_int64_node )
+			      : sizeof (struct ht_int32_node);
+
+	/* Pick a power of 2 that can hold the requested size. */
+	if (size & (size-1) || size < 16) {
+		int req = size;
+		size = 16;
+		while (size < req)
+			size *= 2;
+	}
+
+	if (!(tbl = new(struct hashtable))
+	 || !(tbl->nodes = new_array0(char, size * node_size)))
+		out_of_memory("hashtable_create");
+	tbl->size = size;
+	tbl->entries = 0;
+	tbl->node_size = node_size;
+
+	return tbl;
+}
+
+void hashtable_destroy(struct hashtable *tbl)
+{
+	free(tbl->nodes);
+	free(tbl);
+}
+
+/* This returns the node for the indicated key, either newly created or
+ * already existing.  Returns NULL if not allocating and not found. */
+void *hashtable_find(struct hashtable *tbl, int64 key, int allocate_if_missing)
+{
+	int key64 = (tbl->node_size > sizeof (struct ht_int32_node));
+	struct ht_int32_node *node;
+	uint32 ndx;
+
+	if (allocate_if_missing && tbl->entries > HASH_LOAD_LIMIT(tbl->size)) {
+		void *old_nodes = tbl->nodes;
+		int size = tbl->size * 2;
+		int i;
+
+		if (!(tbl->nodes = new_array0(char, size * tbl->node_size)))
+			out_of_memory("hashtable_node");
+		tbl->size = size;
+		tbl->entries = 0;
+
+		for (i = size / 2; i-- > 0; ) {
+			struct ht_int32_node *move_node = HT_NODE(tbl, old_nodes, i);
+			int64 move_key = HT_KEY(move_node, key64);
+			if (move_key == 0)
+				continue;
+			node = hashtable_find(tbl, move_key, 1);
+			node->data = move_node->data;
+		}
+
+		free(old_nodes);
+	}
+
+	if (!key64) {
+		/* Based on Jenkins One-at-a-time hash. */
+		uchar buf[4], *keyp = buf;
+		int i;
+
+		SIVAL(buf, 0, key);
+		for (ndx = 0, i = 0; i < 4; i++) {
+			ndx += keyp[i];
+			ndx += (ndx << 10);
+			ndx ^= (ndx >> 6);
+		}
+		ndx += (ndx << 3);
+		ndx ^= (ndx >> 11);
+		ndx += (ndx << 15);
+	} else {
+		/* Based on Jenkins hashword() from lookup3.c. */
+		uint32 a, b, c;
+
+		/* Set up the internal state */
+		a = b = c = 0xdeadbeef + (8 << 2);
+
+#define rot(x,k) (((x)<<(k)) ^ ((x)>>(32-(k))))
+		b += (uint32)(key >> 32);
+		a += (uint32)key;
+		c ^= b; c -= rot(b, 14);
+		a ^= c; a -= rot(c, 11);
+		b ^= a; b -= rot(a, 25);
+		c ^= b; c -= rot(b, 16);
+		a ^= c; a -= rot(c, 4);
+		b ^= a; b -= rot(a, 14);
+		c ^= b; c -= rot(b, 24);
+#undef rot
+		ndx = c;
+	}
+
+	/* If it already exists, return the node.  If we're not
+	 * allocating, return NULL if the key is not found. */
+	while (1) {
+		int64 nkey;
+
+		ndx &= tbl->size - 1;
+		node = HT_NODE(tbl, tbl->nodes, ndx);
+		nkey = HT_KEY(node, key64);
+
+		if (nkey == key)
+			return node;
+		if (nkey == 0) {
+			if (!allocate_if_missing)
+				return NULL;
+			break;
+		}
+		ndx++;
+	}
+
+	/* Take over this empty spot and then return the node. */
+	if (key64)
+		((struct ht_int64_node*)node)->key = key;
+	else
+		node->key = key;
+	tbl->entries++;
+	return node;
+}
-- 
2.34.1