tdb.c

samba-3.0.22.tar.gz 编译smb服务器的源码

enum TDB_ERROR tdb_error(TDB_CONTEXT *tdb)
{
	return tdb->ecode;
}

static struct tdb_errname {
	enum TDB_ERROR ecode; const char *estring;
} emap[] = { {TDB_SUCCESS, "Success"},
	     {TDB_ERR_CORRUPT, "Corrupt database"},
	     {TDB_ERR_IO, "IO Error"},
	     {TDB_ERR_LOCK, "Locking error"},
	     {TDB_ERR_OOM, "Out of memory"},
	     {TDB_ERR_EXISTS, "Record exists"},
	     {TDB_ERR_NOLOCK, "Lock exists on other keys"},
	     {TDB_ERR_NOEXIST, "Record does not exist"} };

/* Error string for the last tdb error */
const char *tdb_errorstr(TDB_CONTEXT *tdb)
{
	u32 i;
	for (i = 0; i < sizeof(emap) / sizeof(struct tdb_errname); i++)
		if (tdb->ecode == emap[i].ecode)
			return emap[i].estring;
	return "Invalid error code";
}

/* update an entry in place - this only works if the new data size
   is <= the old data size and the key exists.
   on failure return -1.
*/

static int tdb_update_hash(TDB_CONTEXT *tdb, TDB_DATA key, u32 hash, TDB_DATA dbuf)
{
	struct list_struct rec;
	tdb_off rec_ptr;

	/* find entry */
	if (!(rec_ptr = tdb_find(tdb, key, hash, &rec)))
		return -1;

	/* must be long enough key, data and tailer */
	if (rec.rec_len < key.dsize + dbuf.dsize + sizeof(tdb_off)) {
		tdb->ecode = TDB_SUCCESS; /* Not really an error */
		return -1;
	}

	if (tdb_write(tdb, rec_ptr + sizeof(rec) + rec.key_len,
		      dbuf.dptr, dbuf.dsize) == -1)
		return -1;

	if (dbuf.dsize != rec.data_len) {
		/* update size */
		rec.data_len = dbuf.dsize;
		return rec_write(tdb, rec_ptr, &rec);
	}
 
	return 0;
}

/* find an entry in the database given a key */
/* If an entry doesn't exist tdb_err will be set to
 * TDB_ERR_NOEXIST. If a key has no data attached
 * tdb_err will not be set. Both will return a
 * zero pptr and zero dsize.
 */

TDB_DATA tdb_fetch(TDB_CONTEXT *tdb, TDB_DATA key)
{
	tdb_off rec_ptr;
	struct list_struct rec;
	TDB_DATA ret;
	u32 hash;

	/* find which hash bucket it is in */
	hash = tdb->hash_fn(&key);
	if (!(rec_ptr = tdb_find_lock_hash(tdb,key,hash,F_RDLCK,&rec)))
		return tdb_null;

	if (rec.data_len)
		ret.dptr = tdb_alloc_read(tdb, rec_ptr + sizeof(rec) + rec.key_len,
					  rec.data_len);
	else
		ret.dptr = NULL;
	ret.dsize = rec.data_len;
	tdb_unlock(tdb, BUCKET(rec.full_hash), F_RDLCK);
	return ret;
}

/* check if an entry in the database exists 

   note that 1 is returned if the key is found and 0 is returned if not found
   this doesn't match the conventions in the rest of this module, but is
   compatible with gdbm
*/
static int tdb_exists_hash(TDB_CONTEXT *tdb, TDB_DATA key, u32 hash)
{
	struct list_struct rec;
	
	if (tdb_find_lock_hash(tdb, key, hash, F_RDLCK, &rec) == 0)
		return 0;
	tdb_unlock(tdb, BUCKET(rec.full_hash), F_RDLCK);
	return 1;
}

int tdb_exists(TDB_CONTEXT *tdb, TDB_DATA key)
{
	u32 hash = tdb->hash_fn(&key);
	return tdb_exists_hash(tdb, key, hash);
}

/* record lock stops delete underneath */
static int lock_record(TDB_CONTEXT *tdb, tdb_off off)
{
	return off ? tdb_brlock(tdb, off, F_RDLCK, F_SETLKW, 0) : 0;
}
/*
  Write locks override our own fcntl readlocks, so check it here.
  Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
  an error to fail to get the lock here.
*/
 
static int write_lock_record(TDB_CONTEXT *tdb, tdb_off off)
{
	struct tdb_traverse_lock *i;
	for (i = &tdb->travlocks; i; i = i->next)
		if (i->off == off)
			return -1;
	return tdb_brlock(tdb, off, F_WRLCK, F_SETLK, 1);
}

/*
  Note this is meant to be F_SETLK, *not* F_SETLKW, as it's not
  an error to fail to get the lock here.
*/

static int write_unlock_record(TDB_CONTEXT *tdb, tdb_off off)
{
	return tdb_brlock(tdb, off, F_UNLCK, F_SETLK, 0);
}
/* fcntl locks don't stack: avoid unlocking someone else's */
static int unlock_record(TDB_CONTEXT *tdb, tdb_off off)
{
	struct tdb_traverse_lock *i;
	u32 count = 0;

	if (off == 0)
		return 0;
	for (i = &tdb->travlocks; i; i = i->next)
		if (i->off == off)
			count++;
	return (count == 1 ? tdb_brlock(tdb, off, F_UNLCK, F_SETLKW, 0) : 0);
}

/* actually delete an entry in the database given the offset */
static int do_delete(TDB_CONTEXT *tdb, tdb_off rec_ptr, struct list_struct*rec)
{
	tdb_off last_ptr, i;
	struct list_struct lastrec;

	if (tdb->read_only) return -1;

	if (write_lock_record(tdb, rec_ptr) == -1) {
		/* Someone traversing here: mark it as dead */
		rec->magic = TDB_DEAD_MAGIC;
		return rec_write(tdb, rec_ptr, rec);
	}
	if (write_unlock_record(tdb, rec_ptr) != 0)
		return -1;

	/* find previous record in hash chain */
	if (ofs_read(tdb, TDB_HASH_TOP(rec->full_hash), &i) == -1)
		return -1;
	for (last_ptr = 0; i != rec_ptr; last_ptr = i, i = lastrec.next)
		if (rec_read(tdb, i, &lastrec) == -1)
			return -1;

	/* unlink it: next ptr is at start of record. */
	if (last_ptr == 0)
		last_ptr = TDB_HASH_TOP(rec->full_hash);
	if (ofs_write(tdb, last_ptr, &rec->next) == -1)
		return -1;

	/* recover the space */
	if (tdb_free(tdb, rec_ptr, rec) == -1)
		return -1;
	return 0;
}

/* Uses traverse lock: 0 = finish, -1 = error, other = record offset */
static int tdb_next_lock(TDB_CONTEXT *tdb, struct tdb_traverse_lock *tlock,
			 struct list_struct *rec)
{
	int want_next = (tlock->off != 0);

	/* Lock each chain from the start one. */
	for (; tlock->hash < tdb->header.hash_size; tlock->hash++) {

		/* this is an optimisation for the common case where
		   the hash chain is empty, which is particularly
		   common for the use of tdb with ldb, where large
		   hashes are used. In that case we spend most of our
		   time in tdb_brlock(), locking empty hash chains.

		   To avoid this, we do an unlocked pre-check to see
		   if the hash chain is empty before starting to look
		   inside it. If it is empty then we can avoid that
		   hash chain. If it isn't empty then we can't believe
		   the value we get back, as we read it without a
		   lock, so instead we get the lock and re-fetch the
		   value below.

		   Notice that not doing this optimisation on the
		   first hash chain is critical. We must guarantee
		   that we have done at least one fcntl lock at the
		   start of a search to guarantee that memory is
		   coherent on SMP systems. If records are added by
		   others during the search then thats OK, and we
		   could possibly miss those with this trick, but we
		   could miss them anyway without this trick, so the
		   semantics don't change.

		   With a non-indexed ldb search this trick gains us a
		   factor of around 80 in speed on a linux 2.6.x
		   system (testing using ldbtest).
		 */
		if (!tlock->off && tlock->hash != 0) {
			u32 off;
			if (tdb->map_ptr) {
				for (;tlock->hash < tdb->header.hash_size;tlock->hash++) {
					if (0 != *(u32 *)(TDB_HASH_TOP(tlock->hash) + (unsigned char *)tdb->map_ptr)) {
						break;
					}
				}
				if (tlock->hash == tdb->header.hash_size) {
					continue;
				}
			} else {
				if (ofs_read(tdb, TDB_HASH_TOP(tlock->hash), &off) == 0 &&
				    off == 0) {
					continue;
				}
			}
		}

		if (tdb_lock(tdb, tlock->hash, F_WRLCK) == -1)
			return -1;

		/* No previous record?  Start at top of chain. */
		if (!tlock->off) {
			if (ofs_read(tdb, TDB_HASH_TOP(tlock->hash),
				     &tlock->off) == -1)
				goto fail;
		} else {
			/* Otherwise unlock the previous record. */
			if (unlock_record(tdb, tlock->off) != 0)
				goto fail;
		}

		if (want_next) {
			/* We have offset of old record: grab next */
			if (rec_read(tdb, tlock->off, rec) == -1)
				goto fail;
			tlock->off = rec->next;
		}

		/* Iterate through chain */
		while( tlock->off) {
			tdb_off current;
			if (rec_read(tdb, tlock->off, rec) == -1)
				goto fail;

			/* Detect infinite loops. From "Shlomi Yaakobovich" <[e-mail]>. */
			if (tlock->off == rec->next) {
				TDB_LOG((tdb, 0, "tdb_next_lock: loop detected.\n"));
				goto fail;
			}

			if (!TDB_DEAD(rec)) {
				/* Woohoo: we found one! */
				if (lock_record(tdb, tlock->off) != 0)
					goto fail;
				return tlock->off;
			}

			/* Try to clean dead ones from old traverses */
			current = tlock->off;
			tlock->off = rec->next;
			if (!tdb->read_only && 
			    do_delete(tdb, current, rec) != 0)
				goto fail;
		}
		tdb_unlock(tdb, tlock->hash, F_WRLCK);
		want_next = 0;
	}
	/* We finished iteration without finding anything */
	return TDB_ERRCODE(TDB_SUCCESS, 0);

 fail:
	tlock->off = 0;
	if (tdb_unlock(tdb, tlock->hash, F_WRLCK) != 0)
		TDB_LOG((tdb, 0, "tdb_next_lock: On error unlock failed!\n"));
	return -1;
}

/* traverse the entire database - calling fn(tdb, key, data) on each element.
   return -1 on error or the record count traversed
   if fn is NULL then it is not called
   a non-zero return value from fn() indicates that the traversal should stop
  */
int tdb_traverse(TDB_CONTEXT *tdb, tdb_traverse_func fn, void *private_val)
{
	TDB_DATA key, dbuf;
	struct list_struct rec;
	struct tdb_traverse_lock tl = { NULL, 0, 0 };
	int ret, count = 0;

	/* This was in the initializaton, above, but the IRIX compiler
	 * did not like it.  crh
	 */
	tl.next = tdb->travlocks.next;

	/* fcntl locks don't stack: beware traverse inside traverse */
	tdb->travlocks.next = &tl;

	/* tdb_next_lock places locks on the record returned, and its chain */
	while ((ret = tdb_next_lock(tdb, &tl, &rec)) > 0) {
		count++;
		/* now read the full record */
		key.dptr = tdb_alloc_read(tdb, tl.off + sizeof(rec), 
					  rec.key_len + rec.data_len);
		if (!key.dptr) {
			ret = -1;
			if (tdb_unlock(tdb, tl.hash, F_WRLCK) != 0)
				goto out;
			if (unlock_record(tdb, tl.off) != 0)
				TDB_LOG((tdb, 0, "tdb_traverse: key.dptr == NULL and unlock_record failed!\n"));
			goto out;
		}
		key.dsize = rec.key_len;
		dbuf.dptr = key.dptr + rec.key_len;
		dbuf.dsize = rec.data_len;

		/* Drop chain lock, call out */
		if (tdb_unlock(tdb, tl.hash, F_WRLCK) != 0) {
			ret = -1;
			goto out;
		}
		if (fn && fn(tdb, key, dbuf, private_val)) {
			/* They want us to terminate traversal */
			ret = count;
			if (unlock_record(tdb, tl.off) != 0) {
				TDB_LOG((tdb, 0, "tdb_traverse: unlock_record failed!\n"));;
				ret = -1;
			}
			tdb->travlocks.next = tl.next;
			SAFE_FREE(key.dptr);
			return count;
		}
		SAFE_FREE(key.dptr);
	}
out:
	tdb->travlocks.next = tl.next;
	if (ret < 0)
		return -1;
	else
		return count;
}

/* find the first entry in the database and return its key */
TDB_DATA tdb_firstkey(TDB_CONTEXT *tdb)
{
	TDB_DATA key;
	struct list_struct rec;

	/* release any old lock */
	if (unlock_record(tdb, tdb->travlocks.off) != 0)
		return tdb_null;
	tdb->travlocks.off = tdb->travlocks.hash = 0;

	if (tdb_next_lock(tdb, &tdb->travlocks, &rec) <= 0)
		return tdb_null;
	/* now read the key */
	key.dsize = rec.key_len;
	key.dptr =tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),key.dsize);
	if (tdb_unlock(tdb, BUCKET(tdb->travlocks.hash), F_WRLCK) != 0)
		TDB_LOG((tdb, 0, "tdb_firstkey: error occurred while tdb_unlocking!\n"));
	return key;
}

/* find the next entry in the database, returning its key */
TDB_DATA tdb_nextkey(TDB_CONTEXT *tdb, TDB_DATA oldkey)
{
	u32 oldhash;
	TDB_DATA key = tdb_null;
	struct list_struct rec;
	char *k = NULL;

	/* Is locked key the old key?  If so, traverse will be reliable. */
	if (tdb->travlocks.off) {
		if (tdb_lock(tdb,tdb->travlocks.hash,F_WRLCK))
			return tdb_null;
		if (rec_read(tdb, tdb->travlocks.off, &rec) == -1
		    || !(k = tdb_alloc_read(tdb,tdb->travlocks.off+sizeof(rec),
					    rec.key_len))
		    || memcmp(k, oldkey.dptr, oldkey.dsize) != 0) {
			/* No, it wasn't: unlock it and start from scratch */
			if (unlock_record(tdb, tdb->travlocks.off) != 0)
				return tdb_null;
			if (tdb_unlock(tdb, tdb->travlocks.hash, F_WRLCK) != 0)
				return tdb_null;
			tdb->travlocks.off = 0;
		}

		SAFE_FREE(k);
	}

	if (!tdb->travlocks.off) {
		/* No previous element: do normal find, and lock record */
		tdb->travlocks.off = tdb_find_lock_hash(tdb, oldkey, tdb->hash_fn(&oldkey), F_WRLCK, &rec);
		if (!tdb->travlocks.off)
			return tdb_null;
		tdb->travlocks.hash = BUCKET(rec.full_hash);
		if (lock_record(tdb, tdb->travlocks.off) != 0) {
			TDB_LOG((tdb, 0, "tdb_nextkey: lock_record failed (%s)!\n", strerror(errno)));
			return tdb_null;
		}
	}
	oldhash = tdb->travlocks.hash;

	/* Grab next record: locks chain and returned record,
	   unlocks old record */
	if (tdb_next_lock(tdb, &tdb->travlocks, &rec) > 0) {
		key.dsize = rec.key_len;
		key.dptr = tdb_alloc_read(tdb, tdb->travlocks.off+sizeof(rec),
					  key.dsize);
		/* Unlock the chain of this new record */
		if (tdb_unlock(tdb, tdb->travlocks.hash, F_WRLCK) != 0)
			TDB_LOG((tdb, 0, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
	}
	/* Unlock the chain of old record */
	if (tdb_unlock(tdb, BUCKET(oldhash), F_WRLCK) != 0)
		TDB_LOG((tdb, 0, "tdb_nextkey: WARNING tdb_unlock failed!\n"));
	return key;
}

/* delete an entry in the database given a key */
static int tdb_delete_hash(TDB_CONTEXT *tdb, TDB_DATA key, u32 hash)
{
	tdb_off rec_ptr;
	struct list_struct rec;
	int ret;

	if (!(rec_ptr = tdb_find_lock_hash(tdb, key, hash, F_WRLCK, &rec)))
		return -1;
	ret = do_delete(tdb, rec_ptr, &rec);
	if (tdb_unlock(tdb, BUCKET(rec.full_hash), F_WRLCK) != 0)
		TDB_LOG((tdb, 0, "tdb_delete: WARNING tdb_unlock failed!\n"));
	return ret;
}

int tdb_delete(TDB_CONTEXT *tdb, TDB_DATA key)
{
	u32 hash = tdb->hash_fn(&key);
	return tdb_delete_hash(tdb, key, hash);
}

/* store an element in the database, replacing any existing element
   with the same key 

   return 0 on success, -1 on failure
*/
int tdb_store(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA dbuf, int flag)
{
	struct list_struct rec;
	u32 hash;
	tdb_off rec_ptr;
	char *p = NULL;
	int ret = 0;

	/* find which hash bucket it is in */
	hash = tdb->hash_fn(&key);
	if (tdb_lock(tdb, BUCKET(hash), F_WRLCK) == -1)
		return -1;

	/* check for it existing, on insert. */
	if (flag == TDB_INSERT) {
		if (tdb_exists_hash(tdb, key, hash)) {
			tdb->ecode = TDB_ERR_EXISTS;
			goto fail;
		}
	} else {
		/* first try in-place update, on modify or replace. */
		if (tdb_update_hash(tdb, key, hash, dbuf) == 0)
			goto out;
		if (tdb->ecode == TDB_ERR_NOEXIST &&
		    flag == TDB_MODIFY) {
			/* if the record doesn't exist and we are in TDB_MODIFY mode then
			 we should fail the store */
			goto fail;
	}
	}
	/* reset the error code potentially set by the tdb_update() */
	tdb->ecode = TDB_SUCCESS;

	/* delete any existing record - if it doesn't exist we don't
           care.  Doing this first reduces fragmentation, and avoids
           coalescing with `allocated' block before it's updated. */
	if (flag != TDB_INSERT)
		tdb_delete_hash(tdb, key, hash);

	/* Copy key+value *before* allocating free space in case malloc
	   fails and we are left with a dead spot in the tdb. */

	if (!(p = (char *)malloc(key.dsize + dbuf.dsize))) {
		tdb->ecode = TDB_ERR_OOM;
		goto fail;
	}

	memcpy(p, key.dptr, key.dsize);
	if (dbuf.dsize)
		memcpy(p+key.dsize, dbuf.dptr, dbuf.dsize);

	/* we have to allocate some space */
	if (!(rec_ptr = tdb_allocate(tdb, key.dsize + dbuf.dsize, &rec)))
		goto fail;

	/* Read hash top into next ptr */