<?php
/**
* File contains the ezcArchiveGnuTar class.
*
* @package Archive
* @version 1.4.1
* @copyright Copyright (C) 2005-2010 eZ Systems AS. All rights reserved.
* @license http://ez.no/licenses/new_bsd New BSD License
*/
/**
* The ezcArchiveGnuTar class implements the GNU Tar archive format.
*
* ezcArchiveGnuTar is a subclass from {@link ezcArchive} that provides the common interface,
* and {@link ezcArchiveUstarTar} that provides the basic Tar implementation.
*
* ezcArchiveGnuTar reads on creation only the first {@link ezcArchiveEntry entry} from the archive.
* When needed next entries are read.
*
* The Gnu Tar algorithm is an extension of Ustar Tar. Gnu has the following extended features compared to Ustar:
* - Filenames of unlimited size.
* - File size is unlimited.
*
* The current implementation allows only reading from a Gnu archive.
*
* The features of Gnu Tar and Pax Tar are quite similar, although their approach is different.
*
* @package Archive
* @version 1.4.1
*/
class ezcArchiveGnuTar extends ezcArchiveUstarTar
{
/**
* Initializes the Tar and tries to read the first entry from the archive.
*
* At initialization it sets the blockFactor to $blockFactor. Each tar archive
* has always $blockFactor of blocks ( 0, $blockFactor, 2 * $blockFactor, etc ).
*
* The Tar archive works with blocks, so therefore the first parameter expects
* the archive as a blockFile.
*
* @param ezcArchiveBlockFile $blockFile
* @param int $blockFactor
*/
public function __construct( ezcArchiveBlockFile $blockFile, $blockFactor = 20 )
{
parent::__construct( $blockFile, $blockFactor );
}
/**
* Returns the value which specifies a TAR_GNU algorithm.
*
* @return int
*/
public function getAlgorithm()
{
return self::TAR_GNU;
}
/**
* Returns false because the TAR_PAX algorithm cannot write (yet).
*
* @see isWritable()
*
* @return bool
*/
public function algorithmCanWrite()
{
return false;
}
/**
* Creates the a new pax tar header for this class.
*
* This method expects an {@link ezcArchiveBlockFile} that points to the header that should be
* read (and created). If null is given as block file, an empty header will be created.
*
* @param string|null $file
* @return ezcArchiveGnuHeader
*/
protected function createTarHeader( $file = null)
{
return new ezcArchiveGnuHeader( $file );
}
}
?>
