NAME

Archive::BagIt - The main module to handle bags.

VERSION

version 0.094

NAME

Achive::BagIt - The main module to handle Bags

SOURCE

The original development version was on github at http://github.com/rjeschmi/Archive-BagIt and may be cloned from there.

The actual development version is available at https://git.fsfe.org/art1pirat/Archive-BagIt

Conformance to RFC8493

The module should fulfill the RFC requirements, with following limitations:

only encoding UTF-8 is supported
version 0.97 or 1.0 allowed
version 0.97 requires tag-/manifest-files with md5-fixity
version 1.0 requires tag-/manifest-files with sha512-fixity
BOM is not supported
Carriage Return in bagit-files are not allowed
fetch.txt is unsupported

At the moment only filepaths in linux-style are supported.

To get an more detailled overview, see the testsuite under t/verify_bag.t and corresponding test bags from the BagIt conformance testsuite of Library of Congress under bagit_conformance_suite/.

See https://datatracker.ietf.org/doc/rfc8493/?include_text=1 for details.

TODO

enhanced testsuite
reduce complexity
use modern perl code
add flag to enable very strict verify

FAQ

How to access the manifest-entries directly?

Try this:

   foreach my $algorithm ( keys %{ $self->manifests }) {
       my $entries_ref = $self->manifests->{$algorithm}->manifest_entries();
       # $entries_ref returns a hashref like:
       # {
       #     data/hello.txt   "e7c22b994c59d9cf2b48e549b1e24666636045930d3da7c1acb299d1c3b7f931f94aae41edda2c2b207a36e10f8bcb8d45223e54878f5b316e7ce3b6bc019629"
       # }
   }

Similar for tagmanifests

How fast is Archive::BagIt?

I have made great efforts to optimize Archive::BagIt for high throughput. There are two limiting factors:

calculation of checksums, by switching from the module "Digest" to OpenSSL by using Net::SSLeay a significant speed increase could be achieved.
loading the files referenced in the manifest files was previously done serially and using synchronous I/O. By using the IO::Async module, the files are loaded asynchronously and the checksums are calculated in parallel. If the underlying file system supports parallel accesses, the performance gain is huge.

On my system with 8cores, SSD and a large 9GB bag with 568 payload files the results for verify_bag() are:

                    processing time          run time             throughput
   Version       user time    system time    total time    total    MB/s
    v0.71        38.31s        1.60s         39.938s       100%     230
    v0.81        25.48s        1.68s         27.1s          67%     340
    v0.82        48.85s        3.89s          6.84s         17%    1346

How fast is Archive::BagIt::Fast?

It depends. On my system with 8cores, SSD and a 38MB bag with 48 payload files the results for verify_bag() are:

                  Rate         Base         Fast
   Base         3.01/s           --         -21%
   Fast         3.80/s          26%           --

On my system with 8cores, SSD and a large 9GB bag with 568 payload files the results for verify_bag() are:

                s/iter         Base         Fast
   Base           74.6           --          -9%
   Fast           68.3           9%           --

But you should measure which variant is best for you. In general the default Archive::BagIt is fast enough.

How to update an old bag of version v0.97 to v1.0?

You could try this:

   use Archive::BagIt;
   my $bag=Archive::BagIt->new( $my_old_bag_filepath );
   $bag->load();
   $bag->store();

How to create UTF-8 based paths under MS Windows?

For versions < Windows10: I have no idea and suggestions for a portable solution are very welcome! For Windows 10: Thanks to https://superuser.com/questions/1033088/is-it-possible-to-set-locale-of-a-windows-application-to-utf-8/1451686#1451686 you have to enable UTF-8 support via 'System Administration' -> 'Region' -> 'Administrative' -> 'Region Settings' -> Flag 'Use Unicode UTF-8 for worldwide language support'

Hint: The better way is to use only portable filenames. See perlport for details.

BUGS

There are problems related to Parallel::parallel_map and IO::AIO under MS Windows. The tests are skipped there. Use the parallel feature or the Archive::BagIt::Fast at your own risks on a MS Window System. If you are a MS Windows developer, feel free to send me patches or hints to fix the issues.

THANKS

Thanks to Rob Schmidt <rjeschmi@gmail.com> for the trustful handover of the project and thanks for your initial work! I would also like to thank Patrick Hochstenbach and Rusell McOrmond for their valuable and especially detailed advice! And without the helpful, sometimes rude help of the IRC channel #perl I would have been stuck in a lot of problems. Without the support of my colleagues at SLUB Dresden, the project would never have made it this far.

SYNOPSIS

This modules will hopefully help with the basic commands needed to create and verify a bag. This part supports BagIt 1.0 according to RFC 8493 ([https://tools.ietf.org/html/rfc8493](https://tools.ietf.org/html/rfc8493)).

You only need to know the following methods first:

read a BagIt

    use Archive::BagIt;

    #read in an existing bag:
    my $bag_dir = "/path/to/bag";
    my $bag = Archive::BagIt->new($bag_dir);

construct a BagIt around a payload

    use Archive::BagIt;
    my $bag2 = Archive::BagIt->make_bag($bag_dir);

verify a BagIt-dir

    use Archive::BagIt;

    # Validate a BagIt archive against its manifest
    my $bag3 = Archive::BagIt->new($bag_dir);
    my $is_valid1 = $bag3->verify_bag();

    # Validate a BagIt archive against its manifest, report all errors
    my $bag4 = Archive::BagIt->new($bag_dir);
    my $is_valid2 = $bag4->verify_bag( {report_all_errors => 1} );

read a BagIt-dir, change something, store

Because all methods operate lazy, you should ensure to parse parts of the bag *BEFORE* you modify it. Otherwise it will be overwritten!

    use Archive::BagIt;
    my $bag5 = Archive::BagIt->new($bag_dir); # lazy, nothing happened
    $bag5->load(); # this updates the object representation by parsing the given $bag_dir
    $bag5->store(); # this writes the bag new

METHODS

Constructor

The constructor sub, will create a bag with a single argument,

    use Archive::BagIt;

    #read in an existing bag:
    my $bag_dir = "/path/to/bag";
    my $bag = Archive::BagIt->new($bag_dir);

or use hashreferences

    use Archive::BagIt;

    #read in an existing bag:
    my $bag_dir = "/path/to/bag";
    my $bag = Archive::BagIt->new(
        bag_path => $bag_dir,
    );

The arguments are:

bag_path - path to bag-directory
force_utf8 - if set the warnings about non portable filenames are disabled (default: enabled)
use_async - if set it uses IO::Async to read payload files asynchronly, only useful under Linux.
use_parallel - if set it uses Parallel::parallel_map to calculate digests of payload files in parallel, only useful if underlying filesystem supports parallel read and if multiple CPU cores available.
use_plugins - expected manifest plugin strings, if set it uses the requested plugins, example Archive::BagIt::Plugin::Manifest::SHA256. HINT: this option *disables* the forced fixity check in verify_bag()!

The bag object will use $bag_dir, BUT an existing $bag_dir is not read. If you use store() an existing bag will be overwritten!

See load() if you want to parse/modify an existing bag.

use_parallel()

if set it uses parallel digest processing, default: false

use_async()

if set it uses async IO, default: false

has_force_utf8()

to check if force_utf8() was set.

If set it ignores warnings about potential filepath problems.

bag_path([$new_value])

Getter/setter for bag path

metadata_path()

Getter for metadata path

payload_path()

Getter for payload path

checksum_algos()

Getter for registered Checksums

bag_version()

Getter for bag version

bag_encoding()

Getter for bag encoding.

HINT: the current version of Archive::BagIt only supports UTF-8, but the method could return other values depending on given Bags.

bag_info([$new_value])

Getter/Setter for bag info. Expects/returns an array of HashRefs implementing simple key-value pairs.

HINT: RFC8493 does not allow *reordering* of entries!

has_bag_info()

returns true if bag info exists.

errors()

Getter to return collected errors after a verify_bag() call with Option report_all_errors

warnings()

Getter to return collected warnings after a verify_bag() call

digest_callback()

This method could be reimplemented by derived classes to handle fixity checks in own way. The getter returns an anonymous function with following interface:

   my $digest = $self->digest_callback;
   &$digest( $digestobject, $filename);

This anonymous function MUST use the get_hash_string() function of the Archive::BagIt::Role::Algorithm role, which is implemented by each Archive::BagIt::Plugin::Algorithm::XXXX module.

See Archive::BagIt::Fast for details.

get_baginfo_values_by_key($searchkey)

Returns all values which match $searchkey, undef otherwise

is_baginfo_key_reserved_as_uniq($searchkey)

returns true if key is reserved and should be uniq

is_baginfo_key_reserved( $searchkey )

returns true if key is reserved

verify_baginfo()

checks baginfo-keys, returns true if all fine, otherwise returns undef and the message is pushed to errors(). Warnings pushed to warnings()

delete_baginfo_by_key( $searchkey )

deletes an entry of given $searchkey if exists. If multiple entries with $searchkey exists, only the last one is deleted.

exists_baginfo_key( $searchkey )

returns true if a given $searchkey exists

append_baginfo_by_key($searchkey, $newvalue)

Appends a key value pair to bag_info.

HINT: check return code if append was successful, because some keys needs to be uniq.

add_or_replace_baginfo_by_key($searchkey, $newvalue)

It replaces the first entry with $newvalue if $searchkey exists, otherwise it appends.

forced_fixity_algorithm()

Getter to return the forced fixity algorithm depending on BagIt version

manifest_files()

Getter to find all manifest-files

tagmanifest_files()

Getter to find all tagmanifest-files

payload_files()

Getter to find all payload-files

non_payload_files()

Getter to find all non payload-files

plugins()

Getter/setter to algorithm plugins

manifests()

Getter/Setter to all manifests (objects)

algos()

Getter/Setter to all registered Algorithms

load_plugins

As default SHA512 and MD5 will be loaded and therefore used. If you want to create a bag only with one or a specific checksum-algorithm, you could use this method to (re-)register it. It expects list of strings with namespace of type: Archive::BagIt::Plugin::Algorithm::XXX where XXX is your chosen fixity algorithm.

load()

Triggers loading of an existing bag

verify_bag($opts)

A method to verify a bag deeply. If $opts is set with {return_all_errors} all fixity errors are reported. The default ist to croak with error message if any error is detected.

HINT: You might also want to check Archive::BagIt::Fast to see a more direct way of accessing files (and thus faster).

calc_payload_oxum()

returns an array with octets and streamcount of payload-dir

calc_bagsize()

returns a string with human readable size of paylod

create_bagit()

creates a bagit.txt file

create_baginfo()

creates a bag-info.txt file

Hint: the entries 'Bagging-Date', 'Bag-Software-Agent', 'Payload-Oxum' and 'Bag-Size' will be automagically set, existing values in internal bag-info representation will be overwritten!

store()

store a bagit-obj if bagit directory-structure was already constructed.

init_metadata( $bag_path, $options)

A constructor that will just create the metadata directory

This won't make a bag, but it will create the conditions to do that eventually

make_bag( $bag_path, $options )

A constructor that will make and return a bag from a directory,

It expects a preliminary bagit-dir exists. If there a data directory exists, assume it is already a bag (no checking for invalid files in root)

AVAILABILITY

The latest version of this module is available from the Comprehensive Perl Archive Network (CPAN). Visit http://www.perl.com/CPAN/ to find a CPAN site near you, or see https://metacpan.org/module/Archive::BagIt/.

BUGS AND LIMITATIONS

You can make new bug reports, and view existing ones, through the web interface at http://rt.cpan.org.

AUTHOR

Andreas Romeyke <cpan@andreas.romeyke.de>

COPYRIGHT AND LICENSE

This software is copyright (c) 2022 by Rob Schmidt <rjeschmi@gmail.com>, William Wueppelmann and Andreas Romeyke.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.