1 files changed, 71 insertions, 22 deletions

diff --git a/db2/lock/lock_util.c b/db2/lock/lock_util.c
index 6c1e30f27c..7274a50422 100644
--- a/db2/lock/lock_util.c
+++ b/db2/lock/lock_util.c
@@ -1,25 +1,20 @@
 /*-
  * See the file LICENSE for redistribution information.
  *
- * Copyright (c) 1996, 1997
+ * Copyright (c) 1996, 1997, 1998
  *	Sleepycat Software.  All rights reserved.
  */
 
 #include "config.h"
 
 #ifndef lint
-static const char sccsid[] = "@(#)lock_util.c	10.5 (Sleepycat) 1/8/98";
+static const char sccsid[] = "@(#)lock_util.c	10.9 (Sleepycat) 4/26/98";
 #endif /* not lint */
 
 #ifndef NO_SYSTEM_INCLUDES
 #include <sys/types.h>
 
-#include <fcntl.h>
-#include <stddef.h>
-#include <stdio.h>
-#include <stdlib.h>
 #include <string.h>
-#include <unistd.h>
 #endif
 
 #include "db_int.h"
@@ -30,11 +25,13 @@ static const char sccsid[] = "@(#)lock_util.c	10.5 (Sleepycat) 1/8/98";
 #include "lock.h"
 
 /*
- * This function is used to compare a DBT that is about to be entered
- * into a hash table with an object already in the hash table.  Note
- * that it just returns true on equal and 0 on not-equal.  Therefore this
- * cannot be used as a sort function; its purpose is to be used as a
- * hash comparison function.
+ * __lock_cmp --
+ *	This function is used to compare a DBT that is about to be entered
+ *	into a hash table with an object already in the hash table.  Note
+ *	that it just returns true on equal and 0 on not-equal.  Therefore
+ *	this function cannot be used as a sort function; its purpose is to
+ *	be used as a hash comparison function.
+ *
  * PUBLIC: int __lock_cmp __P((const DBT *, DB_LOCKOBJ *));
  */
 int
@@ -46,6 +43,7 @@ __lock_cmp(dbt, lock_obj)
 
 	if (lock_obj->type != DB_LOCK_OBJTYPE)
 		return (0);
+
 	obj_data = SH_DBT_PTR(&lock_obj->lockobj);
 	return (dbt->size == lock_obj->lockobj.size &&
 		memcmp(dbt->data, obj_data, dbt->size) == 0);
@@ -69,35 +67,86 @@ __lock_locker_cmp(locker, lock_obj)
 }
 
 /*
- * PUBLIC: int __lock_ohash __P((const DBT *));
+ * The next two functions are the hash functions used to store objects in the
+ * lock hash table.  They are hashing the same items, but one (__lock_ohash)
+ * takes a DBT (used for hashing a parameter passed from the user) and the
+ * other (__lock_lhash) takes a DB_LOCKOBJ (used for hashing something that is
+ * already in the lock manager).  In both cases, we have a special check to
+ * fast path the case where we think we are doing a hash on a DB page/fileid
+ * pair.  If the size is right, then we do the fast hash.
+ *
+ * We know that DB uses struct __db_ilocks for its lock objects.  The first
+ * four bytes are the 4-byte page number and the next DB_FILE_ID_LEN bytes
+ * are a unique file id, where the first 4 bytes on UNIX systems are the file
+ * inode number, and the first 4 bytes on Windows systems are the FileIndexLow
+ * bytes.  So, we use the XOR of the page number and the first four bytes of
+ * the file id to produce a 32-bit hash value.
+ *
+ * We have no particular reason to believe that this algorithm will produce
+ * a good hash, but we want a fast hash more than we want a good one, when
+ * we're coming through this code path.
  */
-int
-__lock_ohash(dbt)
-	const DBT *dbt;
-{
-	return (__ham_func5(dbt->data, dbt->size));
+#define FAST_HASH(P) {			\
+	u_int32_t __h;			\
+	u_int8_t *__cp, *__hp;		\
+	__hp = (u_int8_t *)&__h;	\
+	__cp = (u_int8_t *)(P);		\
+	__hp[0] = __cp[0] ^ __cp[4];	\
+	__hp[1] = __cp[1] ^ __cp[5];	\
+	__hp[2] = __cp[2] ^ __cp[6];	\
+	__hp[3] = __cp[3] ^ __cp[7];	\
+	return (__h);			\
 }
 
 /*
- * PUBLIC: u_int32_t __lock_locker_hash __P((u_int32_t));
+ * __lock_ohash --
+ *
+ * PUBLIC: u_int32_t __lock_ohash __P((const DBT *));
  */
 u_int32_t
-__lock_locker_hash(locker)
-	u_int32_t locker;
+__lock_ohash(dbt)
+	const DBT *dbt;
 {
-	return (__ham_func5(&locker, sizeof(locker)));
+	if (dbt->size == sizeof(struct __db_ilock))
+		FAST_HASH(dbt->data);
+
+	return (__ham_func5(dbt->data, dbt->size));
 }
 
 /*
+ * __lock_lhash --
+ *
  * PUBLIC: u_int32_t __lock_lhash __P((DB_LOCKOBJ *));
  */
 u_int32_t
 __lock_lhash(lock_obj)
 	DB_LOCKOBJ *lock_obj;
 {
+	u_int32_t tmp;
 	void *obj_data;
 
 	obj_data = SH_DBT_PTR(&lock_obj->lockobj);
+	if (lock_obj->type == DB_LOCK_LOCKER) {
+		memcpy(&tmp, obj_data, sizeof(u_int32_t));
+		return (tmp);
+	}
+
+	if (lock_obj->lockobj.size == sizeof(struct __db_ilock))
+		FAST_HASH(obj_data);
+
 	return (__ham_func5(obj_data, lock_obj->lockobj.size));
 }
 
+/*
+ * __lock_locker_hash --
+ *	Hash function for entering lockers into the hash table.  Since these
+ *	are simply 32-bit unsigned integers, just return the locker value.
+ *
+ * PUBLIC: u_int32_t __lock_locker_hash __P((u_int32_t));
+ */
+u_int32_t
+__lock_locker_hash(locker)
+	u_int32_t locker;
+{
+	return (locker);
+}