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Filename : archive.php
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<?php
/**
 * File containing the abstract ezcArchive 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 ezcArchive class provides the common interface for reading and writing
 * the archive formats Tar and Zip.
 *
 * ezcArchive provides the main API for reading and writing to an archive. The
 * archive itself can be compressed with GZip or BZip2 and will be handled
 * transparently.
 *
 * The {@link open()} method creates a new archive instance. For
 * existing archives, ezcArchive determines the correct archive format by the
 * mime-type and returns an instance of a subclass handling this format.
 * New archives should force a format type via a parameter in the open()
 * method.
 *
 * The instance of an ezcArchive class is also an iterator, which
 * points to the first file in the archive by default. Moving this pointer can
 * be done via the iterator methods: {@link rewind()}, {@link next()},
 * {@link valid()}, {@link key()}, and {@link current()}. This iterator is
 * defined as an object iterator and allows, for example, the {@link
 * http://www.php.net/foreach foreach} statement to iterate through the files.
 *
 * Extra methods that operate on the current iterator are: {@link
 * extractCurrent()} and {@link appendToCurrent()}. Which can be used,
 * respectively, to extract the files and to append a new file to the archive.
 * To append a directory to an archive you need to add a slash '/' at the end
 * of the directory name.
 *
 * The following example will open an existing tar.gz file and will append each
 * file to a zip archive:
 * <code>
 * $tar = ezcArchive::open( "/tmp/archive.tar.gz" );
 * $newZip = ezcArchive::open( "/tmp/new_archive.zip", ezcArchive::ZIP );
 *
 * foreach ( $tar as $entry )
 * {
 *    // $entry contains the information of the current entry in the archive.
 *    $tar->extractCurrent( "/tmp/" );
 *    $newZip->appendToCurrent( $entry->getPath(), "/tmp/" );
 *    $newZip->next();
 * }
 * </code>
 *
 * In order to extract an entire archive at once, use the {@link extract()}
 * method.
 *
 * @package Archive
 * @version 1.4.1
 * @mainclass
 */
abstract class ezcArchive implements Iterator
{
    /**
     * Normal tar archive.
     */
    const TAR        = 0;

    /**
     * Tar version 7 archive.
     */
    const TAR_V7     = 1;

    /**
     * USTAR tar archive.
     */
    const TAR_USTAR  = 2;

    /**
     * PAX tar archive.
     */
    const TAR_PAX    = 3;

    /**
     * GNU tar archive.
     */
    const TAR_GNU    = 4;

    /**
     * ZIP archive.
     */
    const ZIP        = 10;

    /**
     * Gnu ZIP compression format.
     */
    const GZIP       = 20;

    /**
     * BZIP2 compression format.
     */
    const BZIP2      = 30;

    /**
     * The entry or file number to which the iterator points.
     *
     * The first $fileNumber starts with 0.
     *
     * @var int
     */
    protected $fileNumber = 0;

    /**
     * The number of entries currently read from the archive.
     *
     * @var int
     */
    protected $entriesRead = 0;

    /**
     * Is true when the archive is read until the end, otherwise false.
     *
     * @var bool
     */
    protected $completed = false;

    /**
     * Stores the entries read from the archive.
     *
     * The array is not complete when the {@link $completed} variable is set to
     * false.  The array may be over-complete, so the {@link $entriesRead}
     * should be checked if the {@link $completed} variable is set to true.
     *
     * @var array(ezcArchiveEntry)
     */
    protected $entries;

    /**
     * Direct access to the archive file.
     *
     * @var ezcArchiveFile
     */
    protected $file = null;

    /**
     * Holds the options if passed to the open method.
     *
     * @var ezcArchiveOptions
     */
    protected $options;

    /**
     * Use the {@link open()} method to get an instance of this class.
     */
    private function __construct()
    {
    }

    /**
     * Returns a new ezcArchive instance.
     *
     * This method returns a new instance according to the mime-type or
     * the given $forceType.
     *
     * - If $forceType is set to null, this method will try to determine the
     *   archive format via the file data. Therefore the $forceType can only be
     *   null when the archive contains data.
     * - If $forceType is set, it will use the specified algorithm. Even when
     *   the given archive is from another type than specified.
     *
     * @throws ezcArchiveUnknownTypeException if the type of the archive cannot be determined.
     *
     * @param string  $archiveName  Absolute or relative path to the archive.
     * @param int     $forceType    Open the archive with the $forceType
     *        algorithm. Possible values are: {@link ezcArchive::ZIP},
     *        {@link ezcArchive::TAR}, {@link ezcArchive::TAR_V7}, {@link ezcArchive::TAR_USTAR},
     *        {@link ezcArchive::TAR_PAX}, {@link ezcArchive::TAR_GNU}.
     *        TAR will use the TAR_USTAR algorithm by default.
     * @param ezcArchiveOptions $options
     *
     * @return ezcArchive
     */
    public static function open( $archiveName, $forceType = null, ezcArchiveOptions $options = null )
    {
        $options = self::initOptions( $options );

        if ( !ezcArchiveFile::fileExists( $archiveName ) && $forceType === null )
        {
            throw new ezcArchiveUnknownTypeException( $archiveName );
        }

        if ( $forceType !== null )
        {
            return self::createInstance( $archiveName, $forceType, $options );
        }

        $h = ezcArchiveFileType::detect( $archiveName );

        while ( $h == ezcArchive::GZIP || $h == ezcArchive::BZIP2 )
        {
            if ( $h == ezcArchive::GZIP )
            {
                $archiveName = "compress.zlib://$archiveName";
                $h = ezcArchiveFileType::detect( $archiveName );
            }

            if ( $h == ezcArchive::BZIP2 )
            {
                $archiveName = "compress.bzip2://$archiveName";
                $h = ezcArchiveFileType::detect( $archiveName );
            }
        }

        return self::createInstance( $archiveName, $h, $options );
    }

    /**
     * Close the current archive.
     */
    public function close()
    {
    }

    /**
     * Sets the property $name to $value.
     *
     * Because there are no properties available, this method will always
     * throw an {@link ezcBasePropertyNotFoundException}.
     *
     * @throws ezcBasePropertyNotFoundException if the property does not exist.
     * @param string $name
     * @param mixed $value
     * @ignore
     */
    public function __set( $name, $value )
    {
        throw new ezcBasePropertyNotFoundException( $name );
    }

    /**
     * Returns the property $name.
     *
     * Because there are no properties available, this method will always
     * throw an {@link ezcBasePropertyNotFoundException}.
     *
     * @throws ezcBasePropertyNotFoundException if the property does not exist.
     * @param string $name
     * @ignore
     */
    public function __get( $name )
    {
        throw new ezcBasePropertyNotFoundException( $name );
    }

    /**
     * Returns the algorithm that is used currently.
     *
     * @return int   Possible values are: {@link ezcArchive::ZIP}, {@link ezcArchive::TAR}, {@link ezcArchive::TAR_V7},
     *               {@link ezcArchive::TAR_USTAR}, {@link ezcArchive::TAR_PAX}, or {@link ezcArchive::TAR_GNU}.
     */
    public abstract function getAlgorithm();

    /**
     * Returns true if writing to the archive is implemented, otherwise false.
     *
     * @see isWritable()
     *
     * @return bool
     */
    public abstract function algorithmCanWrite();

    /**
     * Returns an instance of the archive with the given type.
     *
     * Similar to {@link open()}, but the type is required.
     *
     * @param string $archiveName  The path of the archive.
     * @param int    $type        Open the archive with the $forceType
     *        algorithm. Possible values are: {@link ezcArchive::ZIP},
     *        {@link ezcArchive::TAR}, {@link ezcArchive::TAR_V7}, {@link ezcArchive::TAR_USTAR},
     *        {@link ezcArchive::TAR_PAX}, {@link ezcArchive::TAR_GNU}.
     *        TAR will use the TAR_USTAR algorithm by default.
     *
     * @return ezcArchive  Subclass of ezcArchive: {@link ezcArchiveZip},
     *                     {@link ezcArchiveV7Tar}, {@link ezcArchivePax},
     *                     {@link ezcArchiveGnuTar}, or {@link ezcArchiveUstar}.
     */
    protected static function createInstance( $archiveName, $type, ezcArchiveOptions $options = null )
    {
        $options = self::initOptions( $options );

        if ( $type == self::ZIP )
        {
            $af = new ezcArchiveCharacterFile( $archiveName, true, $options->readOnly );
            return self::getZipInstance( $af );
        }

        $af = new ezcArchiveBlockFile( $archiveName, true, 512, $options->readOnly );
        $instance = self::getTarInstance( $af, $type );
        $instance->options = $options;
        return $instance;
    }

    /**
     * This methods initializes the options by generating an options object if $options is null.
     *
     * @param null|ezcArchiveOptions $options
     *
     * @return ezcArchiveOptions
     */
    private static function initOptions( $options )
    {
        if ( $options === null )
        {
            $options = new ezcArchiveOptions;
        }
        return $options;
    }

    /**
     * This method associates a new $options object with this archive.
     *
     * @param ezcArchiveOptions $options
     */
    public function setOptions( ezcArchiveOptions $options )
    {
        $this->options = $options;
    }

    /**
     * Open a tar instance.
     *
     * This method is made public for testing purposes, and should not be used.
     *
     * @param ezcArchiveBlockFile $blockFile
     * @param int    $type
     *        The algorithm type. Possible values are:
     *        {@link ezcArchive::TAR}, {@link ezcArchive::TAR_V7}, {@link ezcArchive::TAR_USTAR},
     *        {@link ezcArchive::TAR_PAX}, {@link ezcArchive::TAR_GNU}.
     *        TAR will use the TAR_USTAR algorithm by default.
     *
     * @return ezcArchive  Subclass of ezcArchive:
     *                     {@link ezcArchiveV7Tar}, {@link ezcArchivePax},
     *                     {@link ezcArchiveGnuTar}, or {@link ezcArchiveUstar}.
     * @access private
     */
    public static function getTarInstance( ezcArchiveBlockFile $blockFile, $type )
    {
        switch ( $type )
        {
            case self::TAR_V7:
                return new ezcArchiveV7Tar( $blockFile );

            case self::TAR_USTAR:
                return new ezcArchiveUstarTar( $blockFile );

            case self::TAR_PAX:
                return new ezcArchivePaxTar( $blockFile );

            case self::TAR_GNU:
                return new ezcArchiveGnuTar( $blockFile );

            case self::TAR:
                return new ezcArchiveUstarTar( $blockFile ); // Default type.
        }

        return null;
    }

    /**
     * Open a zip instance. This method is made public for testing purposes, and
     * should not be used.
     *
     * @param ezcArchiveCharacterFile $charFile  The character file which
     *                                           contains the archive.
     * @return ezcArchive  Subclass of ezcArchive: {@link ezcArchiveZip}.
     * @access private
     */
    public static function getZipInstance( ezcArchiveCharacterFile $charFile )
    {
        return new ezcArchiveZip( $charFile );
    }

    /**
     * Returns true if the iterator points to a valid entry, otherwise false.
     *
     * @return bool
     */
    public function valid()
    {
        return ( $this->fileNumber >= 0 && $this->fileNumber < $this->entriesRead );
    }

    /**
     * Rewinds the iterator to the first entry.
     *
     * @return void
     */
    public function rewind()
    {
        $this->fileNumber = 0;
    }

    /**
     * Returns the current ezcArchiveEntry if it is valid, otherwise false is returned.
     *
     * @return ezcArchiveEntry
     */
    public function current()
    {
        return ( $this->valid() ? $this->entries[$this->fileNumber] : false );
    }

    /**
     * Returns the current key, entry number, if it is valid, otherwise false is returned.
     *
     * @return int
     */
    public function key()
    {
        return ( $this->valid() ? $this->fileNumber : false );
    }

    /**
     * Forwards the iterator to the next entry.
     *
     * If there is no next entry all iterator methods except for {@link
     * rewind()} will return false.
     *
     * @see rewind()
     *
     * @return ezcArchiveEntry  The next entry if it exists, otherwise false.
     */
    public function next()
    {
        if ( $this->valid() )
        {
            $this->fileNumber++;
            if ( $this->valid() )
            {
                return $this->current();
            }

            if ( !$this->completed )
            {
                if ( $this->readCurrentFromArchive() )
                {
                    return $this->current();
                }
            }
        }

        return false;
    }

    /**
     * Extract the current entry to which the iterator points.
     *
     * Extract the current entry to which the iterator points, and return true if the current entry is extracted.
     * If the iterator doesn't point to a valid entry, this method returns false.
     *
     * True if the file is extracted correctly, otherwise false.
     *
     * @param string $target
     *        The full path to which the target should be extracted.
     * @param bool $keepExisting
     *        True if the file shouldn't be overwritten if they already exist.
     *        For the opposite behaviour, false should be given.
     *
     * @throws ezcArchiveValueException     if the archive contains invalid values.
     * @throws ezcBaseFileNotFoundException if the link cannot be found.
     *
     * @return bool
     */
    public function extractCurrent( $target, $keepExisting = false )
    {
        if ( $this->file === null )
        {
            throw new ezcArchiveException( "The archive is closed" );
        }

        if ( !$this->valid() )
        {
            return false;
        }

        $isWindows = ( substr( php_uname( 's' ), 0, 7 ) == 'Windows' ) ? true : false;
        $entry = $this->current();
        $type = $entry->getType();
        $fileName = $target . DIRECTORY_SEPARATOR. $entry->getPath();

        if ( $type == ezcArchiveEntry::IS_LINK )
        {
            $linkName = $target . DIRECTORY_SEPARATOR . $entry->getLink();
            if ( !file_exists( $linkName ) )
            {
                throw new ezcBaseFileNotFoundException( $linkName, "link", "Hard link could not be created." );
            }
        }

        $this->createDefaultDirectory( $fileName );

        if ( !$keepExisting || ( !is_link( $fileName ) && !file_exists( $fileName ) ) )
        {
            if ( ( file_exists( $fileName ) || is_link( $fileName ) ) && !is_dir( $fileName ) )
            {
                unlink ( $fileName );
            }

            if ( !file_exists( $fileName ) ) // For example, directories are not removed.
            {
                switch ( $type )
                {
                    case ezcArchiveEntry::IS_CHARACTER_DEVICE:
                        if ( ezcBaseFeatures::hasFunction( 'posix_mknod' ) )
                        {
                            posix_mknod( $fileName, POSIX_S_IFCHR, $entry->getMajor(), $entry->getMinor() );
                        }
                        else
                        {
                            throw new ezcArchiveValueException( $type );
                        }
                        break;

                    case ezcArchiveEntry::IS_BLOCK_DEVICE:
                        if ( ezcBaseFeatures::hasFunction( 'posix_mknod' ) )
                        {
                            posix_mknod( $fileName, POSIX_S_IFBLK, $entry->getMajor(), $entry->getMinor() );
                        }
                        else
                        {
                            throw new ezcArchiveValueException( $type );
                        }
                        break;

                    case ezcArchiveEntry::IS_FIFO:
                        if ( ezcBaseFeatures::hasFunction( 'posix_mknod' ) )
                        {
                            posix_mknod( $fileName, POSIX_S_IFIFO );
                        }
                        else
                        {
                            throw new ezcArchiveValueException( $type );
                        }
                        break;

                    case ezcArchiveEntry::IS_SYMBOLIC_LINK:
                        if ( $isWindows )
                        {
                            // FIXME.. need to be sure that target file
                            // already extracted before copying it to link destination.
                            $sourcePath = dirname( $fileName ) . '/' . $entry->getLink();
                            $fileName = str_replace( '/', '\\', $fileName );
                            copy( $sourcePath, $fileName );
                        }
                        else
                        {
                            symlink( $entry->getLink(), $fileName );
                        }
                        break;

                    case ezcArchiveEntry::IS_LINK:
                        if ( $isWindows )
                        {
                            copy( $target . DIRECTORY_SEPARATOR . $entry->getLink(), $fileName );
                        }
                        else
                        {
                            link( $target . DIRECTORY_SEPARATOR . $entry->getLink(), $fileName );
                        }
                        break;

                    case ezcArchiveEntry::IS_DIRECTORY:
                        $permissions = $entry->getPermissions();

                        if ( $permissions === null || $permissions === false )
                        {
                            $permissions = '0777';
                        }
                        mkdir( $fileName, octdec( $permissions ), true );
                        break;

                    case ezcArchiveEntry::IS_FILE:
                        $this->writeCurrentDataToFile( $fileName );
                        break;

                    default:
                        throw new ezcArchiveValueException( $type );
                }

                if ( $type == ezcArchiveEntry::IS_SYMBOLIC_LINK &&
                     ezcBaseFeatures::hasFunction( 'posix_geteuid' ) &&
                     posix_geteuid() == 0 )
                {
                    $user = $entry->getUserId();
                    $group = $entry->getGroupId();
                    @lchown( $fileName, $user );
                    @lchgrp( $fileName, $group );
                }

                // Change the username and group if the filename exists and if
                // the intention is to keep it as a file. A zip archive
                // stores the symlinks in a file; thus don't change these.
                if ( file_exists( $fileName ) && ( $type == ezcArchiveEntry::IS_FILE || $type == ezcArchiveEntry::IS_DIRECTORY ) )
                {
                    $group = $entry->getGroupId();
                    $user  = $entry->getUserId();
                    $time  = $entry->getModificationTime();
                    $perms = octdec( $entry->getPermissions() );

                    if ( $this->options && $this->options->extractCallback )
                    {
                        $this->options->extractCallback->{$type == ezcArchiveEntry::IS_DIRECTORY ? 'createDirectoryCallback' : 'createFileCallback'}( $fileName, $perms, $user, $group );
                    }

                    if ( ezcBaseFeatures::hasFunction( 'posix_geteuid' ) &&
                         posix_geteuid() === 0 )
                    {
                        @chgrp( $fileName, $group );
                        @chown( $fileName, $user );
                    }

                    if ( $perms != false )
                    {
                        chmod( $fileName, $perms );
                    }

                    touch( $fileName, $time );
                }
            }

            return true;
        }

        return false;
    }

    /**
     * Search for the entry number.
     *
     * The two parameters here are the same as the PHP {@link http://www.php.net/fseek fseek()} method.
     * The internal iterator position will be set by $offset added to $whence iterations forward.
     * Where $whence is:
     * - SEEK_SET, Set the position equal to $offset.
     * - SEEK_CUR, Set the current position plus $offset.
     * - SEEK_END, Set the last file in archive position plus $offset.
     *
     * This method returns true if the new position is valid, otherwise false.
     *
     * @throws ezcArchiveException
     *         if the archive is closed
     * @param int    $offset
     * @param int    $whence
     * @return bool
     */
    public function seek( $offset, $whence = SEEK_SET )
    {
        if ( $this->file === null )
        {
            throw new ezcArchiveException( "The archive is closed" );
        }

        // Cannot trust the current position if the current position is invalid.
        if ( $whence == SEEK_CUR && $this->valid() == false )
        {
            return false;
        }

        if ( $whence == SEEK_END && !$this->completed )
        {
            // read the entire archive.
             $this->fileNumber = $this->entriesRead;
             while ( $this->readCurrentFromArchive() )
             {
                 $this->fileNumber++;
             }
        }

        switch ( $whence )
        {
            case SEEK_SET:
                $requestedFileNumber = $offset;
                break;

            case SEEK_CUR:
                $requestedFileNumber = $offset + $this->fileNumber;
                break;

            case SEEK_END:
                $requestedFileNumber = $offset + $this->entriesRead - 1;
                break;

            default:
                return false; // Invalid whence.
        }

        $this->fileNumber = $requestedFileNumber;
        if ( $this->valid() )
        {
            return true;
        }

        if ( !$this->completed )
        {
            $this->fileNumber = $this->entriesRead - 1;

            while ( $this->fileNumber != $requestedFileNumber )
            {
                $this->fileNumber++;
                if ( !$this->readCurrentFromArchive() )
                {
                    break;
                }
            }

            return $this->valid();
        }

        return false;
    }

    /**
     * Creates all the directories needed to create the file $file.
     *
     * @param string $file  Path to a file, where all the base directory names will be created.
     */
    protected function createDefaultDirectory( $file )
    {
        // Does the directory exist?
        $dirName = dirname( $file );

        if ( !file_exists( $dirName ) )
        {
            // Try to create the directory.
            if ( substr( php_uname( 's' ), 0, 7 ) == 'Windows' )
            {
                // make all slashes to be '/'
                $dirName = str_replace( '/', '\\', $dirName );
            }

            // Call the callback, to see whether we need to change permissions
            $permissions = 0777;
            $dummy = null;
            if ( $this->options && $this->options->extractCallback )
            {
                $this->options->extractCallback->createDirectoryCallback( $dirName, $permissions, $dummy, $dummy );
            }

            mkdir( $dirName, $permissions, true );
        }
    }

    /**
     * Appends a file to the archive after the current entry.
     *
     * One or multiple files can be added directly after the current file.
     * The remaining entries after the current are removed from the archive!
     *
     * The $files can either be a string or an array of strings. Which, respectively, represents a
     * single file or multiple files.
     *
     * $prefix specifies the begin part of the $files path that should not be included in the archive.
     * The files in the archive are always stored relatively.
     *
     * Example:
     * <code>
     * $tar = ezcArchive( "/tmp/my_archive.tar", ezcArchive::TAR );
     *
     * // Append two files to the end of the archive.
     * $tar->seek( 0, SEEK_END );
     * $tar->appendToCurrent( array( "/home/rb/file1.txt", "/home/rb/file2.txt" ), "/home/rb/" );
     * </code>
     *
     * When multiple files are added to the archive at the same time, thus using an array, does not
     * necessarily produce the same archive as repeatively adding one file to the archive.
     * For example, the Tar archive format, can detect that files hardlink to each other and will store
     * it in a more efficient way.
     *
     * @throws ezcArchiveWriteException  if one of the files cannot be written to the archive.
     * @throws ezcFileReadException      if one of the files cannot be read from the local filesystem.
     *
     * @param string|array(string) $files  Array or a single path to a file.
     * @param string $prefix               First part of the path used in $files.
     * @return bool
     */
    public abstract function appendToCurrent( $files, $prefix );

    /**
     * Appends a file or directory to the end of the archive. Multiple files or directory can
     * be added to the archive when an array is used as input parameter.
     *
     * @see appendToCurrent()
     *
     * @throws ezcArchiveWriteException  if one of the files cannot be written to the archive.
     * @throws ezcFileReadException      if one of the files cannot be read from the local filesystem.
     *
     * @param string|array(string) $files  Array or a single path to a file.
     * @param string $prefix               First part of the path used in $files.
     * @return bool
     */
    public abstract function append( $files, $prefix );

    /**
     * Truncates the archive to $fileNumber of files.
     *
     * The $fileNumber parameter specifies the amount of files that should remain.
     * If the default value, zero, is used then the entire archive file is cleared.
     *
     * @param int $fileNumber
     * @return bool
     */
    public abstract function truncate( $fileNumber = 0 );

    /**
     * Writes the file data from the current entry to the given file.
     *
     * @param string $targetPath  The absolute or relative path of the target file.
     * @return void
     */
    protected abstract function writeCurrentDataToFile( $targetPath );

    /**
     * Returns an array that lists the content of the archive.
     *
     * Use the getArchiveEntry method to get more information about an entry.
     *
     * @see __toString()
     *
     * @throws ezcArchiveException
     *         if the archive is closed
     * @return array(string)
     */
    public function getListing()
    {
        if ( $this->file === null )
        {
            throw new ezcArchiveException( "The archive is closed" );
        }

        $result = array();
        $this->rewind();

        do
        {
            $entry = $this->current();
            $result[] = rtrim( $entry->__toString(), "\n" ); // remove newline.
        } while ( $this->next() );

        return $result;
    }

    /**
     * Returns a string which represents all the entries from the archive.
     *
     * @throws ezcArchiveException
     *         if the archive is closed
     * @return string
     */
    public function __toString()
    {
        if ( $this->file === null )
        {
            throw new ezcArchiveException( "The archive is closed" );
        }

        $result = "";
        $this->rewind();

        while ( $this->valid() )
        {
            $result .= $this->current()->__toString() . "\n";
            $this->next();
        }

        return $result;
    }

    /**
     * Extract entries from the archive to the target directory.
     *
     * All entries from the archive are extracted to the target directory.
     * By default the files in the target directory are overwritten.
     * If the $keepExisting is set to true, the files from the archive will not overwrite existing files.
     *
     * @see extractCurrent()
     *
     * @throws ezcArchiveException
     *         if the archive is closed
     * @throws ezcArchiveEmptyException
     *         if the archive is invalid
     * @param string $target     Absolute or relative path of the directory.
     * @param bool $keepExisting If set to true then the file will be overwritten, otherwise not.
     * @return void
     */
    public function extract( $target, $keepExisting = false )
    {
        if ( $this->file === null )
        {
            throw new ezcArchiveException( "The archive is closed" );
        }

        $this->rewind();
        if ( !$this->valid() )
        {
            throw new ezcArchiveEmptyException( );
        }

        while ( $this->valid() )
        {
            $this->extractCurrent( $target, $keepExisting );
            $this->next();
        }
    }

    /**
     * Returns true if the current archive is empty, otherwise false.
     *
     * @return bool
     */
    public function isEmpty()
    {
        return ( $this->entriesRead == 0 );
    }

    /**
     * Get the file entries from the archive.
     *
     * @param string|array(string) $files  Array or a single path to a file.
     * @param string $prefix               First part of the path used in $files.
     *
     * @return ezcArchiveEntry
     */
    protected function getEntries( $files, $prefix )
    {
        if ( !is_array( $files ) )
        {
            $files = array( $files );
        }

        // Check whether the files are correct.
        foreach ( $files as $file )
        {
            if ( !file_exists( $file ) && !is_link( $file ) )
            {
                throw new ezcBaseFileNotFoundException( $file );
            }
        }

        // Search for all the entries, because otherwise hardlinked files show up as an ordinary file.
        return ezcArchiveEntry::getEntryFromFile( $files, $prefix );
    }
}
?>