File::UStore - Perl extension to store files on a filesystem using a non-hash UUID(Universally Unique Identifier) based randomised storage with depth of storage options.
use File::UStore; my $store = new File::UStore( path => "/home/shantanu/.teststore", prefix => "prefix_", depth => 5 ); open( my $FH, "foo.pl" ) or die "Unable to open file "; # Add a file in the store my $id = $store->add($FH); # Get file handle from id. this might not work if you have too wierd a storage scheme. my $handle = $store->get($id); print <$handle>; # Return the filesystem location of an id my $location = $store->getPath($id); # Remove a file by its id from the store $store->remove("7d4d873e-4bf4-41a5-8696-fd6232f7bdda");
File::UStore is a library that allows users to abstract file storage using a UUID based pointer instead of File Hashes to store the file. This is a critical feature for code which requires even duplicate files to get a unique identifier each time they added to a store. A Hash Storage on the other hand will not allow a file to be duplicated if it is stored multiple time in the store. This can cause issues in cases where a files may be deleted regularly as there would be no way of knowing if a second process is still using the file which the first process might be about to delete.
The current version uses UUID Module to generate universally unique identifiers everytime a file is to be stored.
The Module also provides a option to choose the folder depth at which a file is stored. This can be changed from the default value of 3. Increasing depth is advisable if the store might contain a large number of files in your use case. This will help to avoid having a too large number of files in any single folder.
The object oriented interface to
File::UStore is described in this section.
The following methods are provided:
This constructor returns a new
File::UStore object encapsulating a specific store. The path specifies where the UStore is located on the filesystem. If the path is not specified, the path ~/.ustore is used. The $prefix is an extension to specify the prefix appended before unique file name.
The $file is the handle for the file to be added in the store. The return value is the id ($id) of the $file stored. From this point on the user will only be able to refer to this file using the id. Returns undef on error.
The $id is the file to be removed from the store.
Return false on success and undef on error.
Return the file handle of the file from its id.
Return undef on error.
Return the filesystem location of the file from its id.
Return undef on error.
An Analysis of Compare-by-hash - for reasons why a UUID based storage may be preferred over hash based solution in certain cases. http://www.usenix.org/events/hotos03/tech/full_papers/henson/henson.pdf
File::HStore is a similar module that provides File Hash based storage. However due to the nature of File Hashing,
File::HStore doesn't allow duplicates. If the same file is stored a second time using
File::HStore it transparently returns the same hash it had returned last time as an id without adding any new file in storage due to inherent character of hash based storage, while this is useful if a user doesn't want any duplicates occurring in a storage, this apparently trivial difference is risky in the use case where two processes upload a duplicate file to the store and both processes want to do file handling simultaneously, only one of the processes will be able to get a lock(deletion,manipulation etc.) on the file at a time and if the first process deletes the file referred to by its ID, the second process will never know what happened to the file it added.
Hence to serve this unique use case I wrote this module for a UUID based storage solution which is not hostage to auto de-duping features of HStore. This module returns a unique file id each time a file is uploaded even if its a duplicate of existing file previously uploaded. This allows multiple processes handling data from a common file dump to access the same file. This module also expands on the Hstore to allow the user flexibility of choosing the depth of storage to optimize the performance for the users application. Depth of storage allows users to make the balance between average "number of files in a folder" and folder depth.
<shantanu (dot comes here) bhadoria at gmail dot com> http://www.shantanubhadoria.com.
Please report any bugs or feature requests to
bug-file-ustore at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=File-UStore. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.
You can find documentation for this module with the perldoc command.
You can also look for information at:
Thanks to Alexandre Dulaunoy for the excellent
File::HStore module which along with my own special need provided the idea behind this module.
Copyright (C) 2011 Shantanu Bhadoria
<shantanu (dot comes here) bhadoria at gmail dot com> http://www.shantanubhadoria.com
This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.
See http://dev.perl.org/licenses/ for more information.