NAME
    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.

SYNOPSIS
      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");

DESCRIPTION
    File::UStore is a perl library based on File::HStore to store files on a
    filesystem using a UUID based randomised storage with folder depth
    control over storage.

    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.

SUBROUTINES/METHODS
    The object oriented interface to "File::UStore" is described in this
    section.

    The following methods are provided:

  new
    $store = File::UStore->new( path => "/home/shantanu/.teststore", prefix
    => "prefix_", depth => 5 );
         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.

    $store->add($file)
         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.

    $store->remove($id)
         The $id is the file to be removed from the store.

         Return false on success and undef on error.

    $store->get($id)
         Return the file handle of the file from its id.

         Return undef on error.

    $store->getPath($id)
         Return the filesystem location of the file from its id.

         Return undef on error.

SEE ALSO
    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

USE CASE FOR THIS MODULE IN LIEU OF A HASH BASED STORAGE
    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.

AUTHOR
    Shantanu Bhadoria, "<shantanu (dot comes here) bhadoria at gmail dot
    com>" <http://www.shantanubhadoria.com>.

BUGS
    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.

SUPPORT
    You can find documentation for this module with the perldoc command.

        perldoc File::UStore

    You can also look for information at:

    *   RT: CPAN's request tracker (report bugs here)

        <http://rt.cpan.org/NoAuth/Bugs.html?Dist=File-UStore>

    *   AnnoCPAN: Annotated CPAN documentation

        <http://annocpan.org/dist/File-UStore>

    *   CPAN Ratings

        <http://cpanratings.perl.org/d/File-UStore>

    *   Search CPAN

        <http://search.cpan.org/dist/File-UStore/>

ACKNOWLEDGEMENTS
    Thanks to Alexandre Dulaunoy for the excellent "File::HStore" module
    which along with my own special need provided the idea behind this
    module.

COPYRIGHT AND LICENSE
    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.

MODULE DEPENDENCIES
    UUID

    File::Copy

    File::Path

    File::Spec

