Location: PHPKode > projects > Yioop! > yioop-v0.78/lib/compressors/gzip_compressor.php
<?php
/** 
 *  SeekQuarry/Yioop --
 *  Open Source Pure PHP Search Engine, Crawler, and Indexer
 *
 *  Copyright (C) 2009, 2010, 2011  Chris Pollett hide@address.com
 *
 *  LICENSE:
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 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.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *  END LICENSE
 *
 * @author Chris Pollett hide@address.com
 * @package seek_quarry
 * @subpackage library
 * @license http://www.gnu.org/licenses/ GPL3
 * @link http://www.seekquarry.com/
 * @copyright 2009, 2010, 2011
 * @filesource
 */

if(!defined('BASE_DIR')) {echo "BAD REQUEST"; exit();}

/**
 * Loads the base class if needed 
 */
require_once "compressor.php";

/**
 * Loads utility class for packInt/unpackInt 
 */
require_once BASE_DIR."/lib/utility.php";

 
/**
 * Implementation of a Compressor using GZIP/GUNZIP as the filter.
 * More details on these algorithms can be found at 
 * {@link http://en.wikipedia.org/wiki/Gzip}
 *
 * @author Chris Pollett
 * @package seek_quarry
 * @subpackage library
 */ 
class GzipCompressor implements Compressor
{
    /** Constructor does nothing
     */
    function __construct() {}

    /**
     * Applies the Compressor compress filter to a string before it is inserted 
     * into a WebArchive. In this case, applying the filter means gzipping.
     *
     * @param string $str  string to apply filter to
     * @return string  the result of applying the filter
     */
    function compress($str)
    {
        return gzencode($str, 9);
    }

    /**
     * Used to unapply the compress filter as when data is read out of a 
     * WebArchive. In this case, unapplying the filter means gunzipping.
     *
     * @param string $str  data read from a string archive
     * @return string result of uncompressing
     */
     function uncompress($str)
    {
        return gzinflate(substr($str, 10)); // 10 bytes to skip gzip header
    }

    /**
     * Used to compress an int as a fixed length string in the format of
     * the compression algorithm underlying the compressor. For gzip 
     * we use RFC 1952 http://www.gzip.org/zlib/rfc-gzip.html and we
     * store the int over the modified timestamp in the header of a compressed
     * empty string. Hence, this will always be of fixed length 20.
     *
     * @param int $my_int the integer to compress as a fixed length string
     * @return string the fixed length string containing the packed int
     */
    function compressInt($my_int) 
    {
        return "\x1f\x8b\x08\x00".packInt($my_int) .
            "\x00\x03\x03\x00\x00\x00\x00\x00\x00\x00\x00\x00";
    }

    /**
     * Used to uncompress an int from a fixed length string in the format of
     * the compression algorithm underlying the compressor. For gzip 
     * we use RFC 1952 http://www.gzip.org/zlib/rfc-gzip.html and we
     * store the int over the modified timestamp in the header of a compressed
     * empty string. This has length 4 bytes starting at byte 4 of the
     * gzip header.
     *
     * @param string $my_compressed_int the fixed length string containing 
     *      the packed int to extract
     * @return int the integer contained in that string
     */
    function uncompressInt($my_compressed_int) 
    {
        return unpackInt(substr($my_compressed_int,4,4));
    }

    /**
     * Computes the length of an int when packed using the underlying
     * compression algorithm as a fixed length string. For gzip 
     * we use RFC 1952 http://www.gzip.org/zlib/rfc-gzip.html and we
     * store the int over the modified timestamp in the header of a compressed
     * empty string. Hence, this will always be of fixed length 20.
     *
     * @return int length of int as a fixed length compressed string
     */
    function compressedIntLen() 
    {
        return 20;
    }

    /**
     * File extension that should be associated with this compressor
     * @return string name of dos file extension
     */
    static function fileExtension()
    {
        return ".txt.gz";
    }
} 
?>
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