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


version 0.08


Achive::BagIt - The main module to handle Bags


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

The actual development version is available at [https://art1pirat.spdns.org/art1/Archive-BagIt](https://art1pirat.spdns.org/art1/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](https://datatracker.ietf.org/doc/rfc8493/?include_text=1) for details.


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


## 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 of form:
        # $entries_ref->{$algorithm}->{$file} = $digest;

Similar for tagmanifests

## How fast is `Archive::BagIt::Fast`?

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

                   Rate        Base         Fast
    Base         102%           --         -10%
    Fast         125%           11%           --

On network filesystem (CIFS, 1Gb) with same Bag:

                   Rate         Fast         Base
    Fast         2.20/s          --          -11%
    Base         2.48/s          13%         --

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 );

## 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](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](https://metacpan.org/pod/perlport) for details.


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


## 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)

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.

## 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

## 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()

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 )

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)


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


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


Rob Schmidt <rjeschmi@gmail.com>


This software is copyright (c) 2021 by Rob Schmidt and 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.