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