From: Willy Tarreau <w@1wt.eu>
Date: Wed, 24 Nov 2010 13:01:45 +0000 (+0100)
Subject: [CLEANUP] hash: move the avalanche hash code globally available
X-Git-Tag: v1.5-dev8~360
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4c14eaa0d4e1a9338da8aeb254de51fe47d17ed3;p=thirdparty%2Fhaproxy.git

[CLEANUP] hash: move the avalanche hash code globally available

We'll use this hash at other places, let's make it globally available.
The function has also been renamed because its "chash_hash" name was
not appropriate.
---

diff --git a/include/common/standard.h b/include/common/standard.h
index bdb6ec0fba..3990e6ffab 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -442,4 +442,28 @@ const char *quote_arg(const char *ptr);
 /* returns an operator among STD_OP_* for string <str> or < 0 if unknown */
 int get_std_op(const char *str);
 
+/* hash a 32-bit integer to another 32-bit integer */
+extern unsigned int full_hash(unsigned int a);
+static inline unsigned int __full_hash(unsigned int a)
+{
+	/* This function is one of Bob Jenkins' full avalanche hashing
+	 * functions, which when provides quite a good distribution for little
+	 * input variations. The result is quite suited to fit over a 32-bit
+	 * space with enough variations so that a randomly picked number falls
+	 * equally before any server position.
+	 * Check http://burtleburtle.net/bob/hash/integer.html for more info.
+	 */
+	a = (a+0x7ed55d16) + (a<<12);
+	a = (a^0xc761c23c) ^ (a>>19);
+	a = (a+0x165667b1) + (a<<5);
+	a = (a+0xd3a2646c) ^ (a<<9);
+	a = (a+0xfd7046c5) + (a<<3);
+	a = (a^0xb55a4f09) ^ (a>>16);
+
+	/* ensure values are better spread all around the tree by multiplying
+	 * by a large prime close to 3/4 of the tree.
+	 */
+	return a * 3221225473U;
+}
+
 #endif /* _COMMON_STANDARD_H */
diff --git a/src/lb_chash.c b/src/lb_chash.c
index 58c029a4ad..a2582f0680 100644
--- a/src/lb_chash.c
+++ b/src/lb_chash.c
@@ -7,7 +7,7 @@
  * robin because we'll use it to replace the previous map-based implementation
  * which offered both algorithms.
  *
- * Copyright 2000-2009 Willy Tarreau <w@1wt.eu>
+ * Copyright 2000-2010 Willy Tarreau <w@1wt.eu>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -19,6 +19,7 @@
 #include <common/compat.h>
 #include <common/config.h>
 #include <common/debug.h>
+#include <common/standard.h>
 #include <eb32tree.h>
 
 #include <types/global.h>
@@ -27,28 +28,6 @@
 #include <proto/backend.h>
 #include <proto/queue.h>
 
-static inline unsigned int chash_hash(unsigned int a)
-{
-	/* This function is one of Bob Jenkins' full avalanche hashing
-	 * functions, which when provides quite a good distribution for little
-	 * input variations. The result is quite suited to fit over a 32-bit
-	 * space with enough variations so that a randomly picked number falls
-	 * equally before any server position.
-	 * Check http://burtleburtle.net/bob/hash/integer.html for more info.
-	 */
-	a = (a+0x7ed55d16) + (a<<12);
-	a = (a^0xc761c23c) ^ (a>>19);
-	a = (a+0x165667b1) + (a<<5);
-	a = (a+0xd3a2646c) ^ (a<<9);
-	a = (a+0xfd7046c5) + (a<<3);
-	a = (a^0xb55a4f09) ^ (a>>16);
-
-	/* ensure values are better spread all around the tree by multiplying
-	 * by a large prime close to 3/4 of the tree.
-	 */
-	return a * 3221225473U;
-}
-
 /* Return next tree node after <node> which must still be in the tree, or be
  * NULL. Lookup wraps around the end to the beginning. If the next node is the
  * same node, return NULL. This is designed to find a valid next node before
@@ -292,7 +271,7 @@ struct server *chash_get_server_hash(struct proxy *p, unsigned int hash)
 	else
 		return NULL;
 
-	hash = chash_hash(hash);
+	hash = full_hash(hash);
 
 	/* find the node after and the node before */
 	next = eb32_lookup_ge(root, hash);
@@ -418,7 +397,7 @@ void chash_init_server_tree(struct proxy *p)
 
 		for (node = 0; node < srv->lb_nodes_tot; node++) {
 			srv->lb_nodes[node].server = srv;
-			srv->lb_nodes[node].node.key = chash_hash(srv->puid * SRV_EWGHT_RANGE + node);
+			srv->lb_nodes[node].node.key = full_hash(srv->puid * SRV_EWGHT_RANGE + node);
 		}
 
 		if (srv_is_usable(srv->state, srv->eweight))
diff --git a/src/standard.c b/src/standard.c
index 60f5af1f5d..1ab2194128 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -1106,6 +1106,12 @@ int get_std_op(const char *str)
 	return ret;
 }
 
+/* hash a 32-bit integer to another 32-bit integer */
+unsigned int full_hash(unsigned int a)
+{
+	return __full_hash(a);
+}
+
 /*
  * Local variables:
  *  c-indent-level: 8