MDV::Packdrakeng

Section: User Contributed Perl Documentation (3)
Updated: 2007-08-09
Page Index

NAME

MDV::Packdrakeng - Simple Archive Extractor/Builder

SYNOPSIS

    use MDV::Packdrakeng;

    # creating an archive
    $pack = MDV::Packdrakeng->new(archive => "myarchive.cz");
    # Adding a few files
    $pack->add("/path/", "file1", "file2");
    # Adding an unamed file
    open($handle, "file");
    $pack->add_virtual("filename", $handle);
    close($handle);

    $pack = undef;

    # extracting an archive
    $pack = MDV::Packdrakeng->open(archive => "myarchive.cz");
    # listing files
    $pack->list();
    # extracting few files
    $pack->extract("/path/", "file1", "file2");
    # extracting data into a file handle
    open($handle, "file");
    $pack->extract_virtual($handle, "filename");
    close($handle);

DESCRIPTION

"MDV::Packdrakeng" is a simple indexed archive builder and extractor using standard compression methods.

IMPLEMENTATION

Compressed data are stored by block. For example,

 UncompresseddatA1UncompresseddatA2 UncompresseddatA3UncompresseddatA4
 |--- size  1 ---||--- size  2 ---| |--- size  3 ---||--- size  4 ---|
 |<-offset1       |<-offset2        |<-offset3       |<-offset4

gives:

 CompresseD1CompresseD2 CompresseD3CompresseD4
 |--- c. size 1, 2 ---| |--- c. size 3, 4 ---|
 |<-c. offset 1, 2      |<-c. offset 3, 4

A new block is started when its size exceeds the "block_size" value.

Compressed data are followed by the table of contents (toc), that is, a simple list of packed files. Each file name is terminated by the "\n" character:

    dir1
    dir2
    ...
    dirN
    symlink1
    point_file1
    symlink2
    point_file2
    ...
    ...
    symlinkN
    point_fileN
    file1
    file2
    ...
    fileN

The file sizes follows, 4 values are stored for each file: offset into archive of compressed block, size of compressed block, offset into block of the file and the file's size.

Finally the archive contains a 64-byte trailer, about the toc and the archive itself:

    'cz[0', strings 4 bytes
    number of directory, 4 bytes
    number of symlinks, 4 bytes
    number of files, 4 bytes
    the toc size, 4 bytes
    the uncompression command, string of 40 bytes length
    '0]cz', string 4 bytes

FUNCTIONS

new(%options)

Creates a new archive. Options:

archive: The file name of the archive. If the file doesn't exist, it will be created, else it will be owerwritten. See "open".
compress: The application to use to compress, if unspecified, gzip is used.
uncompress: The application used to extract data from archive. This option is useless if you're opening an existing archive (unless you want to force it). If unset, this value is based on compress command followed by '-d' argument.
extern: If you're using gzip, by default MDV::Packdrakeng will use perl-zlib to save system ressources. This option forces MDV::Packdrakeng to use the external gzip command. This has no meaning with other compress programs as internal functions are not implemented yet.
comp_level: The compression level passed as an argument to the compression program. By default, this is set to 6.
block_size: The limit size after which we start a new compressed block. The default value is 400KB. Set it to 0 to be sure a new block will be started for each packed files, and -1 to never start a new block. Be aware that a big block size will slow down the file extraction.
quiet: Do not output anything, shut up.
debug: Print debug messages.

open(%options)

Opens an existing archive for extracting or adding files.

The uncompression command is found into the archive, and the compression command is deduced from it.

If you add files, a new compressed block will be started even if the last block is smaller than the value of the "block_size" option. If some compression options can't be found in the archive, the new preference will be applied.

Options are the same than for the "new()" function.

MDV::Packdrakeng->add_virtual($type, $filename, $data)

Adds a file into archive according passed information. $type gives the type of the file:

  - 'd', the file will be a directory, store as '$filename'. $data is not used.
  - 'l', the file will be a symlink named $filename, pointing to the file whose path
    is given by the string $data.
  - 'f', the file is a normal file, $filename will be its name, $data is either
         an handle to open file, data will be read from current position to the
         end of file, either a string to push as the content of the file.

MDV::Packdrakeng->add($prefix, @files)

Adds @files into archive located into $prefix. Only directory, files and symlink will be added. For each file, the path should be relative to $prefix and is stored as is.

MDV::Packdrakeng->extract_virtual(*HANDLE, $filename)

Extracts $filename data from archive into the *HANDLE. $filename should be a normal file.

MDV::Packdrakeng->extract($destdir, @files)

Extracts @files from the archive into $destdir prefix.

MDV::Packdrakeng->getcontent()

Returns three arrayrefs describing files files into archive, respectively directory list, files list and symlink list.

MDV::Packdrakeng->infofile($file)

Returns type and information about a given file into the archive; that is:

  - 'f' and the the size of the file for a plain file
  - 'l' and the linked file for a symlink
  - 'd' and undef for a directory
  - undef if the file can't be found into archive.

MDV::Packdrakeng->infofile($handle)

Print to $handle (STDOUT if not specified) the content of the archive.

MDV::Packdrakeng->dumptoc($handle)

Print to $handle (STDOUT if not specified) the table of content of the archive.

CHANGELOG

1.10

use an oo code
add_virtual() now accept a string as file content

AUTHOR

Olivier Thauvin <nanardon@mandriva.org>, Rafael Garcia-Suarez <rgarciasuarez@mandriva.com>

This module is a from scratch-rewrite of the original "packdrake" utility. Its format is fully compatible with the old packdrake.

LICENSE

This program is free software; you can redistribute it and/or modify it under the terms of GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

If you do not have a copy of the GNU General Public License write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.