tdb.c

自己精简过的PPPD代码。在嵌入中应用可以更好的发挥。比原先的小了很多

*/
static int tdb_append_inplace(TDB_CONTEXT *tdb, TDB_DATA key, u32 hash, TDB_DATA new_dbuf)
{
	struct list_struct rec;
	tdb_off rec_ptr;

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

	/* Append of 0 is always ok. */
	if (new_dbuf.dsize == 0)
		return 0;

	/* must be long enough for key, old data + new data and tailer */
	if (rec.rec_len < key.dsize + rec.data_len + new_dbuf.dsize + sizeof(tdb_off)) {
		/* No room. */
		tdb->ecode = TDB_SUCCESS; /* Not really an error */
		return -1;
	}

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

	/* update size */
	rec.data_len += new_dbuf.dsize;
	return rec_write(tdb, rec_ptr, &rec);
}

/* Append to an entry. Create if not exist. */

int tdb_append(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA new_dbuf)
{
	struct list_struct rec;
	u32 hash;
	tdb_off rec_ptr;
	char *p = NULL;
	int ret = 0;
	size_t new_data_size = 0;

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

	/* first try in-place. */
	if (tdb_append_inplace(tdb, key, hash, new_dbuf) == 0)
		goto out;

	/* reset the error code potentially set by the tdb_append_inplace() */
	tdb->ecode = TDB_SUCCESS;

	/* find entry */
	if (!(rec_ptr = tdb_find(tdb, key, hash, &rec))) {
		if (tdb->ecode != TDB_ERR_NOEXIST)
			goto fail;

		/* Not found - create. */

		ret = tdb_store(tdb, key, new_dbuf, TDB_INSERT);
		goto out;
	}

	new_data_size = rec.data_len + new_dbuf.dsize;

	/* Copy key+old_value+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 + new_data_size))) {
		tdb->ecode = TDB_ERR_OOM;
		goto fail;
	}

	/* Copy the key in place. */
	memcpy(p, key.dptr, key.dsize);

	/* Now read the old data into place. */
	if (rec.data_len &&
		tdb_read(tdb, rec_ptr + sizeof(rec) + rec.key_len, p + key.dsize, rec.data_len, 0) == -1)
			goto fail;

	/* Finally append the new data. */
	if (new_dbuf.dsize)
		memcpy(p+key.dsize+rec.data_len, new_dbuf.dptr, new_dbuf.dsize);

	/* 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. */

	tdb_delete_hash(tdb, key, hash);

	if (!(rec_ptr = tdb_allocate(tdb, key.dsize + new_data_size, &rec)))
		goto fail;

	/* Read hash top into next ptr */
	if (ofs_read(tdb, TDB_HASH_TOP(hash), &rec.next) == -1)
		goto fail;

	rec.key_len = key.dsize;
	rec.data_len = new_data_size;
	rec.full_hash = hash;
	rec.magic = TDB_MAGIC;

	/* write out and point the top of the hash chain at it */
	if (rec_write(tdb, rec_ptr, &rec) == -1
	    || tdb_write(tdb, rec_ptr+sizeof(rec), p, key.dsize+new_data_size)==-1
	    || ofs_write(tdb, TDB_HASH_TOP(hash), &rec_ptr) == -1) {
		/* Need to tdb_unallocate() here */
		goto fail;
	}

 out:
	SAFE_FREE(p); 
	tdb_unlock(tdb, BUCKET(hash), F_WRLCK);
	return ret;

fail:
	ret = -1;
	goto out;
}

static int tdb_already_open(dev_t device,
			    ino_t ino)
{
	TDB_CONTEXT *i;
	
	for (i = tdbs; i; i = i->next) {
		if (i->device == device && i->inode == ino) {
			return 1;
		}
	}

	return 0;
}

/* This is based on the hash algorithm from gdbm */
static u32 default_tdb_hash(TDB_DATA *key)
{
	u32 value;	/* Used to compute the hash value.  */
	u32   i;	/* Used to cycle through random values. */

	/* Set the initial value from the key size. */
	for (value = 0x238F13AF * key->dsize, i=0; i < key->dsize; i++)
		value = (value + (key->dptr[i] << (i*5 % 24)));

	return (1103515243 * value + 12345);  
}

/* open the database, creating it if necessary 

   The open_flags and mode are passed straight to the open call on the
   database file. A flags value of O_WRONLY is invalid. The hash size
   is advisory, use zero for a default value.

   Return is NULL on error, in which case errno is also set.  Don't 
   try to call tdb_error or tdb_errname, just do strerror(errno).

   @param name may be NULL for internal databases. */
TDB_CONTEXT *tdb_open(const char *name, int hash_size, int tdb_flags,
		      int open_flags, mode_t mode)
{
	return tdb_open_ex(name, hash_size, tdb_flags, open_flags, mode, NULL, NULL);
}


TDB_CONTEXT *tdb_open_ex(const char *name, int hash_size, int tdb_flags,
			 int open_flags, mode_t mode,
			 tdb_log_func log_fn,
			 tdb_hash_func hash_fn)
{
	TDB_CONTEXT *tdb;
	struct stat st;
	int rev = 0, locked = 0;
	unsigned char *vp;
	u32 vertest;

	if (!(tdb = calloc(1, sizeof *tdb))) {
		/* Can't log this */
		errno = ENOMEM;
		goto fail;
	}
	tdb->fd = -1;
	tdb->name = NULL;
	tdb->map_ptr = NULL;
	tdb->flags = tdb_flags;
	tdb->open_flags = open_flags;
	tdb->log_fn = log_fn;
	tdb->hash_fn = hash_fn ? hash_fn : default_tdb_hash;

	if ((open_flags & O_ACCMODE) == O_WRONLY) {
		TDB_LOG((tdb, 0, "tdb_open_ex: can't open tdb %s write-only\n",
			 name));
		errno = EINVAL;
		goto fail;
	}
	
	if (hash_size == 0)
		hash_size = DEFAULT_HASH_SIZE;
	if ((open_flags & O_ACCMODE) == O_RDONLY) {
		tdb->read_only = 1;
		/* read only databases don't do locking or clear if first */
		tdb->flags |= TDB_NOLOCK;
		tdb->flags &= ~TDB_CLEAR_IF_FIRST;
	}

	/* internal databases don't mmap or lock, and start off cleared */
	if (tdb->flags & TDB_INTERNAL) {
		tdb->flags |= (TDB_NOLOCK | TDB_NOMMAP);
		tdb->flags &= ~TDB_CLEAR_IF_FIRST;
		if (tdb_new_database(tdb, hash_size) != 0) {
			TDB_LOG((tdb, 0, "tdb_open_ex: tdb_new_database failed!"));
			goto fail;
		}
		goto internal;
	}

	if ((tdb->fd = open(name, open_flags, mode)) == -1) {
		TDB_LOG((tdb, 5, "tdb_open_ex: could not open file %s: %s\n",
			 name, strerror(errno)));
		goto fail;	/* errno set by open(2) */
	}

	/* ensure there is only one process initialising at once */
	if (tdb_brlock(tdb, GLOBAL_LOCK, F_WRLCK, F_SETLKW, 0) == -1) {
		TDB_LOG((tdb, 0, "tdb_open_ex: failed to get global lock on %s: %s\n",
			 name, strerror(errno)));
		goto fail;	/* errno set by tdb_brlock */
	}

	/* we need to zero database if we are the only one with it open */
	if ((tdb_flags & TDB_CLEAR_IF_FIRST) &&
		(locked = (tdb_brlock(tdb, ACTIVE_LOCK, F_WRLCK, F_SETLK, 0) == 0))) {
		open_flags |= O_CREAT;
		if (ftruncate(tdb->fd, 0) == -1) {
			TDB_LOG((tdb, 0, "tdb_open_ex: "
				 "failed to truncate %s: %s\n",
				 name, strerror(errno)));
			goto fail; /* errno set by ftruncate */
		}
	}

	if (read(tdb->fd, &tdb->header, sizeof(tdb->header)) != sizeof(tdb->header)
	    || strcmp(tdb->header.magic_food, TDB_MAGIC_FOOD) != 0
	    || (tdb->header.version != TDB_VERSION
		&& !(rev = (tdb->header.version==TDB_BYTEREV(TDB_VERSION))))) {
		/* its not a valid database - possibly initialise it */
		if (!(open_flags & O_CREAT) || tdb_new_database(tdb, hash_size) == -1) {
			errno = EIO; /* ie bad format or something */
			goto fail;
		}
		rev = (tdb->flags & TDB_CONVERT);
	}
	vp = (unsigned char *)&tdb->header.version;
	vertest = (((u32)vp[0]) << 24) | (((u32)vp[1]) << 16) |
		  (((u32)vp[2]) << 8) | (u32)vp[3];
	tdb->flags |= (vertest==TDB_VERSION) ? TDB_BIGENDIAN : 0;
	if (!rev)
		tdb->flags &= ~TDB_CONVERT;
	else {
		tdb->flags |= TDB_CONVERT;
		convert(&tdb->header, sizeof(tdb->header));
	}
	if (fstat(tdb->fd, &st) == -1)
		goto fail;

	/* Is it already in the open list?  If so, fail. */
	if (tdb_already_open(st.st_dev, st.st_ino)) {
		TDB_LOG((tdb, 2, "tdb_open_ex: "
			 "%s (%d,%d) is already open in this process\n",
			 name, (int)st.st_dev, (int)st.st_ino));
		errno = EBUSY;
		goto fail;
	}

	if (!(tdb->name = (char *)strdup(name))) {
		errno = ENOMEM;
		goto fail;
	}

	tdb->map_size = st.st_size;
	tdb->device = st.st_dev;
	tdb->inode = st.st_ino;
	tdb->locked = calloc(tdb->header.hash_size+1, sizeof(tdb->locked[0]));
	if (!tdb->locked) {
		TDB_LOG((tdb, 2, "tdb_open_ex: "
			 "failed to allocate lock structure for %s\n",
			 name));
		errno = ENOMEM;
		goto fail;
	}
	tdb_mmap(tdb);
	if (locked) {
		if (!tdb->read_only)
			if (tdb_clear_spinlocks(tdb) != 0) {
				TDB_LOG((tdb, 0, "tdb_open_ex: "
				"failed to clear spinlock\n"));
				goto fail;
			}
		if (tdb_brlock(tdb, ACTIVE_LOCK, F_UNLCK, F_SETLK, 0) == -1) {
			TDB_LOG((tdb, 0, "tdb_open_ex: "
				 "failed to take ACTIVE_LOCK on %s: %s\n",
				 name, strerror(errno)));
			goto fail;
		}

	}

	/* We always need to do this if the CLEAR_IF_FIRST flag is set, even if
	   we didn't get the initial exclusive lock as we need to let all other
	   users know we're using it. */

	if (tdb_flags & TDB_CLEAR_IF_FIRST) {
		/* leave this lock in place to indicate it's in use */
		if (tdb_brlock(tdb, ACTIVE_LOCK, F_RDLCK, F_SETLKW, 0) == -1)
			goto fail;
	}


 internal:
	/* Internal (memory-only) databases skip all the code above to
	 * do with disk files, and resume here by releasing their
	 * global lock and hooking into the active list. */
	if (tdb_brlock(tdb, GLOBAL_LOCK, F_UNLCK, F_SETLKW, 0) == -1)
		goto fail;
	tdb->next = tdbs;
	tdbs = tdb;
	return tdb;

 fail:
	{ int save_errno = errno;

	if (!tdb)
		return NULL;
	
	if (tdb->map_ptr) {
		if (tdb->flags & TDB_INTERNAL)
			SAFE_FREE(tdb->map_ptr);
		else
			tdb_munmap(tdb);
	}
	SAFE_FREE(tdb->name);
	if (tdb->fd != -1)
		if (close(tdb->fd) != 0)
			TDB_LOG((tdb, 5, "tdb_open_ex: failed to close tdb->fd on error!\n"));
	SAFE_FREE(tdb->locked);
	SAFE_FREE(tdb);
	errno = save_errno;
	return NULL;
	}
}

/**
 * Close a database.
 *
 * @returns -1 for error; 0 for success.
 **/
int tdb_close(TDB_CONTEXT *tdb)
{
	TDB_CONTEXT **i;
	int ret = 0;

	if (tdb->map_ptr) {
		if (tdb->flags & TDB_INTERNAL)
			SAFE_FREE(tdb->map_ptr);
		else
			tdb_munmap(tdb);
	}
	SAFE_FREE(tdb->name);
	if (tdb->fd != -1)
		ret = close(tdb->fd);
	SAFE_FREE(tdb->locked);

	/* Remove from contexts list */
	for (i = &tdbs; *i; i = &(*i)->next) {
		if (*i == tdb) {
			*i = tdb->next;
			break;
		}
	}

	memset(tdb, 0, sizeof(*tdb));
	SAFE_FREE(tdb);

	return ret;
}

/* lock/unlock entire database */
int tdb_lockall(TDB_CONTEXT *tdb)
{
	u32 i;

	/* There are no locks on read-only dbs */
	if (tdb->read_only)
		return TDB_ERRCODE(TDB_ERR_LOCK, -1);
	for (i = 0; i < tdb->header.hash_size; i++) 
		if (tdb_lock(tdb, i, F_WRLCK))
			break;

	/* If error, release locks we have... */
	if (i < tdb->header.hash_size) {
		u32 j;

		for ( j = 0; j < i; j++)
			tdb_unlock(tdb, j, F_WRLCK);
		return TDB_ERRCODE(TDB_ERR_NOLOCK, -1);
	}

	return 0;
}
void tdb_unlockall(TDB_CONTEXT *tdb)
{
	u32 i;
	for (i=0; i < tdb->header.hash_size; i++)
		tdb_unlock(tdb, i, F_WRLCK);
}

/* lock/unlock one hash chain. This is meant to be used to reduce
   contention - it cannot guarantee how many records will be locked */
int tdb_chainlock(TDB_CONTEXT *tdb, TDB_DATA key)
{
	return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
}

int tdb_chainunlock(TDB_CONTEXT *tdb, TDB_DATA key)
{
	return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_WRLCK);
}

int tdb_chainlock_read(TDB_CONTEXT *tdb, TDB_DATA key)
{
	return tdb_lock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
}

int tdb_chainunlock_read(TDB_CONTEXT *tdb, TDB_DATA key)
{
	return tdb_unlock(tdb, BUCKET(tdb->hash_fn(&key)), F_RDLCK);
}


/* register a loging function */
void tdb_logging_function(TDB_CONTEXT *tdb, void (*fn)(TDB_CONTEXT *, int , const char *, ...))
{
	tdb->log_fn = fn;
}

/* reopen a tdb - this can be used after a fork to ensure that we have an independent
   seek pointer from our parent and to re-establish locks */
int tdb_reopen(TDB_CONTEXT *tdb)
{
	struct stat st;

	if (tdb->flags & TDB_INTERNAL)
		return 0; /* Nothing to do. */
	if (tdb_munmap(tdb) != 0) {
		TDB_LOG((tdb, 0, "tdb_reopen: munmap failed (%s)\n", strerror(errno)));
		goto fail;
	}
	if (close(tdb->fd) != 0)
		TDB_LOG((tdb, 0, "tdb_reopen: WARNING closing tdb->fd failed!\n"));
	tdb->fd = open(tdb->name, tdb->open_flags & ~(O_CREAT|O_TRUNC), 0);
	if (tdb->fd == -1) {
		TDB_LOG((tdb, 0, "tdb_reopen: open failed (%s)\n", strerror(errno)));
		goto fail;
	}
	if (fstat(tdb->fd, &st) != 0) {
		TDB_LOG((tdb, 0, "tdb_reopen: fstat failed (%s)\n", strerror(errno)));
		goto fail;
	}
	if (st.st_ino != tdb->inode || st.st_dev != tdb->device) {
		TDB_LOG((tdb, 0, "tdb_reopen: file dev/inode has changed!\n"));
		goto fail;
	}
	tdb_mmap(tdb);
	if ((tdb->flags & TDB_CLEAR_IF_FIRST) && (tdb_brlock(tdb, ACTIVE_LOCK, F_RDLCK, F_SETLKW, 0) == -1)) {
		TDB_LOG((tdb, 0, "tdb_reopen: failed to obtain active lock\n"));
		goto fail;
	}

	return 0;

fail:
	tdb_close(tdb);
	return -1;
}

/* reopen all tdb's */
int tdb_reopen_all(void)
{
	TDB_CONTEXT *tdb;

	for (tdb=tdbs; tdb; tdb = tdb->next) {
		/* Ensure no clear-if-first. */
		tdb->flags &= ~TDB_CLEAR_IF_FIRST;
		if (tdb_reopen(tdb) != 0)
			return -1;
	}

	return 0;
}