<?php
/**
 * SeekQuarry/Yioop --
 * Open Source Pure PHP Search Engine, Crawler, and Indexer
 *
 * Copyright (C) 2009 - 2026  Chris Pollett chris@pollett.org
 *
 * 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 <https://www.gnu.org/licenses/>.
 *
 * END LICENSE
 *
 * @author Chris Pollett chris@pollett.org
 * @license https://www.gnu.org/licenses/ GPL3
 * @link https://www.seekquarry.com/
 * @copyright 2009 - 2026
 * @filesource
 */
namespace seekquarry\yioop\library\compressors;

use seekquarry\yioop\configs as C;
use seekquarry\yioop\library as L;

/**
 * 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
 */
class GzipCompressor implements Compressor
{
    /** Constructor does nothing
     */
    public function __construct() {}
    /**
     * Applies the Compressor compress filter to a string and returns the
     * resultsting string. In this case, applying the filter means gzipping.
     *
     * @param string $str  string to apply filter to
     * @return string  the result of applying the filter
     */
    public function compress($str)
    {
        return gzencode($str, 9);
    }
    /**
     * Applies the Compressor gzip filter to a string $str and
     * then writes it to file $file_name
     *
     * @param string $file_name  to write string to
     * @param string $str  string to apply filter to
     * @return int  the number of bytes written
     */
    public function compressPutFile($file_name, $str)
    {
        $gz_str = gzencode($str, 9);
        return file_put_contents($file_name, $gz_str);
    }
    /**
     * 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 $str  data read from a string archive
     * @return string result of uncompressing
     */
     public function uncompress($str)
    {
        $skip_header_string = substr($str, 10);// 10 bytes to skip gzip header
        return (!empty($skip_header_string)) ?
            gzinflate($skip_header_string) : "";
    }
    /**
     * Applies the Compressor uncompress filter to the contents read
     * from $file_name and returns the result as a string
     *
     * @param string $file_name  to write string to
     * @return string the uncompressed contents of the $file_name
     */
    public function uncompressGetFile($file_name)
    {
        $str = file_get_contents($file_name);
        $skip_header_string = substr($str, 10);// 10 bytes to skip gzip header
        return (!empty($skip_header_string)) ?
            gzinflate($skip_header_string) : "";
    }
    /**
     * 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 https://tools.ietf.org/html/rfc1952 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 $my_int the integer to compress as a fixed length string
     * @return string the fixed length string containing the packed int
     */
    public function compressInt($my_int)
    {
        return "\x1f\x8b\x08\x00". L\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 https://tools.ietf.org/html/rfc1952 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 $my_compressed_int the fixed length string containing
     *     the packed int to extract
     * @return int the integer contained in that string
     */
    public function uncompressInt($my_compressed_int)
    {
        return L\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
     */
    public function compressedIntLen()
    {
        return 20;
    }
    /**
     * File extension that should be associated with this compressor
     * @return string name of dos file extension
     */
    public static function fileExtension()
    {
        return ".txt.gz";
    }
}
