1/*- 2 * See the file LICENSE for redistribution information. 3 * 4 * Copyright (c) 1996,2008 Oracle. All rights reserved. 5 * 6 * $Id: lock_util.c,v 12.11 2008/01/08 20:58:41 bostic Exp $ 7 */ 8 9#include "db_config.h" 10 11#include "db_int.h" 12#include "dbinc/db_page.h" 13#include "dbinc/hash.h" 14#include "dbinc/lock.h" 15 16/* 17 * The next two functions are the hash functions used to store objects in the 18 * lock hash tables. They are hashing the same items, but one (__lock_ohash) 19 * takes a DBT (used for hashing a parameter passed from the user) and the 20 * other (__lock_lhash) takes a DB_LOCKOBJ (used for hashing something that is 21 * already in the lock manager). In both cases, we have a special check to 22 * fast path the case where we think we are doing a hash on a DB page/fileid 23 * pair. If the size is right, then we do the fast hash. 24 * 25 * We know that DB uses DB_LOCK_ILOCK types for its lock objects. The first 26 * four bytes are the 4-byte page number and the next DB_FILE_ID_LEN bytes 27 * are a unique file id, where the first 4 bytes on UNIX systems are the file 28 * inode number, and the first 4 bytes on Windows systems are the FileIndexLow 29 * bytes. So, we use the XOR of the page number and the first four bytes of 30 * the file id to produce a 32-bit hash value. 31 * 32 * We have no particular reason to believe that this algorithm will produce 33 * a good hash, but we want a fast hash more than we want a good one, when 34 * we're coming through this code path. 35 */ 36#define FAST_HASH(P) { \ 37 u_int32_t __h; \ 38 u_int8_t *__cp, *__hp; \ 39 __hp = (u_int8_t *)&__h; \ 40 __cp = (u_int8_t *)(P); \ 41 __hp[0] = __cp[0] ^ __cp[4]; \ 42 __hp[1] = __cp[1] ^ __cp[5]; \ 43 __hp[2] = __cp[2] ^ __cp[6]; \ 44 __hp[3] = __cp[3] ^ __cp[7]; \ 45 return (__h); \ 46} 47 48/* 49 * __lock_ohash -- 50 * 51 * PUBLIC: u_int32_t __lock_ohash __P((const DBT *)); 52 */ 53u_int32_t 54__lock_ohash(dbt) 55 const DBT *dbt; 56{ 57 if (dbt->size == sizeof(DB_LOCK_ILOCK)) 58 FAST_HASH(dbt->data); 59 60 return (__ham_func5(NULL, dbt->data, dbt->size)); 61} 62 63/* 64 * __lock_lhash -- 65 * 66 * PUBLIC: u_int32_t __lock_lhash __P((DB_LOCKOBJ *)); 67 */ 68u_int32_t 69__lock_lhash(lock_obj) 70 DB_LOCKOBJ *lock_obj; 71{ 72 void *obj_data; 73 74 obj_data = SH_DBT_PTR(&lock_obj->lockobj); 75 76 if (lock_obj->lockobj.size == sizeof(DB_LOCK_ILOCK)) 77 FAST_HASH(obj_data); 78 79 return (__ham_func5(NULL, obj_data, lock_obj->lockobj.size)); 80} 81 82/* 83 * __lock_nomem -- 84 * Report a lack of some resource. 85 * 86 * PUBLIC: int __lock_nomem __P((ENV *, const char *)); 87 */ 88int 89__lock_nomem(env, res) 90 ENV *env; 91 const char *res; 92{ 93 __db_errx(env, "Lock table is out of available %s", res); 94 return (ENOMEM); 95} 96