Tie::DB_FileLock 0.10

Tie::DB_FileLock is a Perl module that offers locking access to Berkeley DB 1.x.

SYNOPSIS

 use Tie::DB_FileLock;

 [$X =] tie %hash, 'Tie::DB_FileLock', [$file, $flags, $mode, $DB_HASH];
 [$X =] tie %hash, 'Tie::DB_FileLock', $file, $flags, $mode, $DB_BTREE;

 $X->debug($value);

 $status = $X->del($key [, $flags]);
 $status = $X->put($key, $value [, $flags]);
 $status = $X->get($key, $value [, $flags]);
 $status = $X->seq($key, $value, $flags);
 $status = $X->sync([$flags]);
 $status = $X->fd();

 # BTREE only
 $count = $X->get_dup($key);
 @list = $X->get_dup($key);
 %list = $X->get_dup($key, 1);
 $status = $X->find_dup($key, $value);
 $status = $X->del_dup($key, $value);

 # DBM Filters
 $old_filter = $db->filter_store_key ( sub { ... } );
 $old_filter = $db->filter_store_value( sub { ... } );
 $old_filter = $db->filter_fetch_key ( sub { ... } );
 $old_filter = $db->filter_fetch_value( sub { ... } );

 [undef $X;]
 untie %hash;

Module DB_File allows perl to tie hashes to on-disk dbm files, but fails to provide any method by which the hashes might be locked, providing exclusive access or preventing page-level collisions. Tie::DB_FileLock extends DB_File, providing a locking layer using flock().

Unlike Tie::DB_Lock, Tie::DB_FileLock does not duplicate files to allow concurrent access for readers and writers. Tie::DB_FileLock is therefore suitable for large dbms with relatively short locking periods.

Tie::DB_FileLock is designed as a drop-in replacement for DB_File, requiring minimal code changes. Change all occurrences of "DB_File" to "Tie::DB_FileLock" and all should be well. DB_RECNO is not presently supported by Tie::DB_FileLock.

Arguments to Tie::DB_FileLock are identical as those to DB_File. The dbm is locked for shared access if opened RO, exclusively otherwise. The default, as in DB_File, is read/write/create.

Use of the predefined references $DB_HASH, $DB_BTREE, and $DB_RECNO, is identical as with DB_File. When creating your own, the new call is the same, but the object created is a DB_File::XXX thing and not a Tie::DB_FileLock::XXX thing -- therefore error messages will refer to DB_File::XXX.


Product's homepage

Requirements:

· Perl