<?php
class tar {
	var $filename;
	var $isGzipped;
	var $tar_file;
	
	var $files;
	var $directories;
	var $numFiles;
	var $numDirectories;

	function tar() {
		return true;
	}

	/**
	 * Computes the unsigned Checksum of a file's header
     * to try to ensure valid file
     * 
     * @param	string  $bytestring
     * 
     * @access	private
	 */
	function __computeUnsignedChecksum($bytestring)
	{
		$unsigned_chksum = '';
		for($i=0; $i<512; $i++)
			$unsigned_chksum += ord($bytestring[$i]);
		for($i=0; $i<8; $i++)
			$unsigned_chksum -= ord($bytestring[148 + $i]);
		$unsigned_chksum += ord(" ") * 8;

		return $unsigned_chksum;
	}


	/**
	 * Converts a NULL padded string to a non-NULL padded string
	 * 
	 * @param   string  $string
     * 
	 * @return  string 
     * 
     * @access	private
	 **/
	function __parseNullPaddedString($string)
	{
		$position = strpos($string,chr(0));
		return substr($string,0,$position);
	}

	/**
	 * This function parses the current TAR file
	 * 
	 * @return  bool    always TRUE
     * 
     * @access	private
	 **/
	function __parseTar()
	{
		// Read Files from archive
		$tar_length = strlen($this->tar_file);
		$main_offset = 0;
		$this->numFiles = 0;
		while ( $main_offset < $tar_length ) {
			// If we read a block of 512 nulls, we are at the end of the archive
			if(substr($this->tar_file,$main_offset,512) == str_repeat(chr(0),512))
				break;

			// Parse file name
			$file_name		= $this->__parseNullPaddedString(substr($this->tar_file,$main_offset,100));

			// Parse the file mode
			$file_mode		= substr($this->tar_file,$main_offset + 100,8);

			// Parse the file user ID
			$file_uid		= octdec(substr($this->tar_file,$main_offset + 108,8));

			// Parse the file group ID
			$file_gid		= octdec(substr($this->tar_file,$main_offset + 116,8));

			// Parse the file size
			$file_size		= octdec(substr($this->tar_file,$main_offset + 124,12));

			// Parse the file update time - unix timestamp format
			$file_time		= octdec(substr($this->tar_file,$main_offset + 136,12));

			// Parse Checksum
			$file_chksum		= octdec(substr($this->tar_file,$main_offset + 148,6));

			// Parse user name
			$file_uname		= $this->__parseNullPaddedString(substr($this->tar_file,$main_offset + 265,32));

			// Parse Group name
			$file_gname		= $this->__parseNullPaddedString(substr($this->tar_file,$main_offset + 297,32));

			// Make sure our file is valid
			if($this->__computeUnsignedChecksum(substr($this->tar_file,$main_offset,512)) != $file_chksum)
				return false;

			// Parse File Contents
			$file_contents		= substr($this->tar_file,$main_offset + 512,$file_size);

			/*	### Unused Header Information ###
				$activeFile["typeflag"]		= substr($this->tar_file,$main_offset + 156,1);
				$activeFile["linkname"]		= substr($this->tar_file,$main_offset + 157,100);
				$activeFile["magic"]		= substr($this->tar_file,$main_offset + 257,6);
				$activeFile["version"]		= substr($this->tar_file,$main_offset + 263,2);
				$activeFile["devmajor"]		= substr($this->tar_file,$main_offset + 329,8);
				$activeFile["devminor"]		= substr($this->tar_file,$main_offset + 337,8);
				$activeFile["prefix"]		= substr($this->tar_file,$main_offset + 345,155);
				$activeFile["endheader"]	= substr($this->tar_file,$main_offset + 500,12);
			*/

			if ( $file_size > 0 ) {
				// Increment number of files
				$this->numFiles++;

				// Create us a new file in our array
				$activeFile = &$this->files[];

				// Asign Values
				$activeFile["name"]		= $file_name;
				$activeFile["mode"]		= $file_mode;
				$activeFile["size"]		= $file_size;
				$activeFile["time"]		= $file_time;
				$activeFile["user_id"]		= $file_uid;
				$activeFile["group_id"]		= $file_gid;
				$activeFile["user_name"]	= $file_uname;
				$activeFile["group_name"]	= $file_gname;
				$activeFile["checksum"]		= $file_chksum;
				$activeFile["file"]		= $file_contents;
			} else {
				// Increment number of directories
				$this->numDirectories++;

				// Create a new directory in our array
				$activeDir = &$this->directories[];

				// Assign values
				$activeDir["name"]		= $file_name;
				$activeDir["mode"]		= $file_mode;
				$activeDir["time"]		= $file_time;
				$activeDir["user_id"]		= $file_uid;
				$activeDir["group_id"]		= $file_gid;
				$activeDir["user_name"]		= $file_uname;
				$activeDir["group_name"]	= $file_gname;
				$activeDir["checksum"]		= $file_chksum;
			}

			// Move our offset the number of blocks we have processed
			$main_offset += 512 + (ceil($file_size / 512) * 512);
		}

		return true;
	}

	/**
	 * Read a non gzipped tar file in for processing.
	 * 
	 * @param   string  $filename   full filename
	 * @return  bool    always TRUE
     * 
     * @access	private
	 **/
	function __readTar($filename='')
	{
		// Set the filename to load
		if(!$filename)
			$filename = $this->filename;

		// Read in the TAR file
		$fp = fopen($filename,"rb");
		$this->tar_file = fread($fp,filesize($filename));
		fclose($fp);

		if($this->tar_file[0] == chr(31) && $this->tar_file[1] == chr(139) && $this->tar_file[2] == chr(8)) {
			if(!function_exists("gzinflate"))
				return false;

			$this->isGzipped = true;

			$this->tar_file = gzinflate(substr($this->tar_file,10,-4));
		}

		// Parse the TAR file
		$this->__parseTar();

		return true;
	}

	/**
	 * Generates a TAR file from the processed data
	 * 
	 * @return  bool    always TRUE
     * 
     * @access	private
	 **/
	function __generateTAR() {
		$this->tar_file = '';

		// Generate Records for each directory, if we have directories
		if($this->numDirectories > 0) {
			foreach($this->directories as $key => $information) {
				unset($header);

				// Generate tar header for this directory
				// Filename, Permissions, UID, GID, size, Time, checksum, typeflag, linkname, magic, version, user name, group name, devmajor, devminor, prefix, end
				$header = str_pad($information["name"],100,chr(0));
				$header .= str_pad(decoct($information["mode"]),7,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information["user_id"]),7,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information["group_id"]),7,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct(0),11,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information["time"]),11,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_repeat(" ",8);
				$header .= "5";
				$header .= str_repeat(chr(0),100);
				$header .= str_pad("ustar",6,chr(32));
				$header .= chr(32) . chr(0);
				$header .= str_pad("",32,chr(0));
				$header .= str_pad("",32,chr(0));
				$header .= str_repeat(chr(0),8);
				$header .= str_repeat(chr(0),8);
				$header .= str_repeat(chr(0),155);
				$header .= str_repeat(chr(0),12);

				// Compute header checksum
				$checksum = str_pad(decoct($this->__computeUnsignedChecksum($header)),6,"0",STR_PAD_LEFT);
				for($i=0; $i<6; $i++) {
					$header[(148 + $i)] = substr($checksum,$i,1);
				}
				$header[154] = chr(0);
				$header[155] = chr(32);

				// Add new tar formatted data to tar file contents
				$this->tar_file .= $header;
			}
		}

		// Generate Records for each file, if we have files (We should...)
		if($this->numFiles > 0) {
			foreach($this->files as $key => $information) {
				// Generate the TAR header for this file
				// Filename, Permissions, UID, GID, size, Time, checksum, typeflag, linkname, magic, version, user name, group name, devmajor, devminor, prefix, end
				$header = str_pad($information['name'], 100, chr(0));
				$header .= str_pad(decoct($information['mode']),7,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information['user_id']),7,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information['group_id']),7,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information['size']),11,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_pad(decoct($information['time']),11,"0",STR_PAD_LEFT) . chr(0);
				$header .= str_repeat(" ",8);
				$header .= "0";
				$header .= str_repeat(chr(0),100);
				$header .= str_pad("ustar",6,chr(32));
				$header .= chr(32) . chr(0);
				$header .= str_pad($information["user_name"],32,chr(0));	// How do I get a file's user name from PHP?
				$header .= str_pad($information["group_name"],32,chr(0));	// How do I get a file's group name from PHP?
				$header .= str_repeat(chr(0),8);
				$header .= str_repeat(chr(0),8);
				$header .= str_repeat(chr(0),155);
				$header .= str_repeat(chr(0),12);

				// Compute header checksum
				$checksum = str_pad(decoct($this->__computeUnsignedChecksum($header)),6,"0",STR_PAD_LEFT);
				for($i=0; $i<6; $i++) {
					$header[(148 + $i)] = substr($checksum,$i,1);
				}
				$header[154] = chr(0);
				$header[155] = chr(32);

				// Pad file contents to byte count divisible by 512
				$file_contents = str_pad($information["file"],(ceil($information["size"] / 512) * 512),chr(0));

				// Add new tar formatted data to tar file contents
				$this->tar_file .= $header . $file_contents;
			}
		}

		// Add 512 bytes of NULLs to designate EOF
		$this->tar_file .= str_repeat(chr(0),512);

		return true;
	}


	/**
	 * Open a TAR file
	 * 
	 * @param   string  $filename
	 * @return  bool 
	 **/
	function openTAR($filename)
	{
		// Clear any values from previous tar archives
		unset($this->filename);
		unset($this->isGzipped);
		unset($this->tar_file);
		unset($this->files);
		unset($this->directories);
		unset($this->numFiles);
		unset($this->numDirectories);

		// If the tar file doesn't exist...
		if(!file_exists($filename))
			return false;

		$this->filename = $filename;

		// Parse this file
		$this->__readTar();

		return true;
	}

	/**
	 * Appends a tar file to the end of the currently opened tar file.
	 * 
	 * @param   string  $filename
	 * @return  bool
	 **/
	function appendTar($filename)
	{
		// If the tar file doesn't exist...
		if(!file_exists($filename))
			return false;

		$this->__readTar($filename);

		return true;
	}

	/**
	 * Retrieves information about a file in the current tar archive
	 * 
	 * @param   string  $filename
	 * @return  string  FALSE on fail
	 **/
	function getFile($filename)
	{
		if ( $this->numFiles > 0 ) {
			foreach($this->files as $key => $information) {
				if($information["name"] == $filename)
					return $information;
			}
		}

		return false;
	}

	/**
	 * Retrieves information about a directory in the current tar archive
	 * 
	 * @param   string  $dirname
	 * @return  string  FALSE on fail
	 **/
	function getDirectory($dirname)
	{
		if($this->numDirectories > 0) {
			foreach($this->directories as $key => $information) {
				if($information["name"] == $dirname)
					return $information;
			}
		}

		return false;
	}

	/**
	 * Check if this tar archive contains a specific file
	 * 
	 * @param   string  $filename
	 * @return  bool
	 **/
	function containsFile($filename)
	{
		if ( $this->numFiles > 0 ) {
			foreach($this->files as $key => $information) {
				if($information["name"] == $filename)
					return true;
			}
		}
		return false;
	}

	/**
	 * Check if this tar archive contains a specific directory
	 * 
	 * @param   string  $dirname
	 * @return  bool
	 **/
	function containsDirectory($dirname)
	{
		if ( $this->numDirectories > 0 ) {
			foreach ( $this->directories as $key => $information ) {
				if ( $information["name"] == $dirname ) {
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Add a directory to this tar archive
	 * 
	 * @param   string  $dirname
	 * @return  bool
	 **/
	function addDirectory($dirname, $recurse = false)
	{
		if ( !file_exists($dirname) ) {
			return false;
		}

		// Get directory information
		$file_information = stat($dirname);

		// Add directory to processed data
		$this->numDirectories++;
		$activeDir		= &$this->directories[];
		$activeDir["name"]	= $dirname;
		$activeDir["mode"]	= @$file_information["mode"];
		$activeDir["time"]	= @$file_information["time"];
		$activeDir["user_id"]	= @$file_information["uid"];
		$activeDir["group_id"]	= @$file_information["gid"];
		$activeDir["checksum"]	= 0;

		if($recurse){
			$cdir = opendir($dirname);
			while($element = readdir($cdir)){
				if($element != '.' && $element != '..'){
					if(is_dir($dirname . '/' . $element)){
						$this->addDirectory($dirname . '/' . $element, true);
					} else {
						$this->addFile($dirname . '/' . $element);
					}
				}
			}
			closedir($cdir);
		}
		
		return true;
	}

	/**
	 * Add a file to the tar archive
	 * 
	 * @param   string  $filename
	 * @param   boolean $binary     Binary file?
	 * @return  bool
	 **/
	function addFile($filename, $binary = false)
	{
		// Make sure the file we are adding exists!
		if ( !file_exists($filename) ) {
			return false;
		}

		// Make sure there are no other files in the archive that have this same filename
		if ( $this->containsFile($filename) ) {
			return false;
		}

		// Get file information
		$file_information = stat($filename);

		// Read in the file's contents
		if (!$binary) {
			$fp = fopen($filename, "r");
		} else {
			$fp = fopen($filename, "rb");
		}
		if(filesize($filename) !== 0) $file_contents = fread($fp, filesize($filename));
		else $file_contents = '';
		fclose($fp);

		// Add file to processed data
		$this->numFiles++;
		$activeFile			= &$this->files[];
		$activeFile["name"]		= $filename;
		$activeFile["mode"]		= $file_information["mode"];
		$activeFile["user_id"]		= $file_information["uid"];
		$activeFile["group_id"]		= $file_information["gid"];
		$activeFile["size"]		= $file_information["size"];
		$activeFile["time"]		= $file_information["mtime"];
		$activeFile["checksum"]		= isset($checksum) ? $checksum : '';
		$activeFile["user_name"]	= "";
		$activeFile["group_name"]	= "";
		$activeFile["file"]		= trim($file_contents);

		return true;
	}

	/**
	 * Remove a file from the tar archive
	 * 
	 * @param   string  $filename
	 * @return  bool
	 **/
	function removeFile($filename)
	{
		if ( $this->numFiles > 0 ) {
			foreach ( $this->files as $key => $information ) {
				if ( $information["name"] == $filename ) {
					$this->numFiles--;
					unset($this->files[$key]);
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Remove a directory from the tar archive
	 * 
	 * @param   string  $dirname
	 * @return  bool
	 **/
	function removeDirectory($dirname)
	{
		if ( $this->numDirectories > 0 ) {
			foreach ( $this->directories as $key => $information ) {
				if ( $information["name"] == $dirname ) {
					$this->numDirectories--;
					unset($this->directories[$key]);
					return true;
				}
			}
		}
		return false;
	}

	/**
	 * Write the currently loaded tar archive to disk
	 * 
	 * @return  bool 
	 **/
	function saveTar()
	{
		if ( !$this->filename ) {
			return false;
		}

		// Write tar to current file using specified gzip compression
		$this->toTar($this->filename,$this->isGzipped);

		return true;
	}

	/**
	 * Saves tar archive to a different file than the current file
	 * 
	 * @param   string  $filename
	 * @param   bool    $useGzip    Use GZ compression?
	 * @return  bool
	 **/
	function toTar($filename, $useGzip) {
		if(!$filename) {
			return false;
		}
		// Encode processed files into TAR file format
		$this->__generateTar();

		// GZ Compress the data if we need to
		if ( $useGzip ) {
			// Make sure we have gzip support
			if ( !function_exists("gzencode") ) {
				return false;
			}

			$file = gzencode($this->tar_file);
		} else {
			$file = $this->tar_file;
		}

		// Write the TAR file
		$fp = fopen($filename,"wb");
		fwrite($fp,$file);
		fclose($fp);

		return true;
	}

	/**
	 * Sends tar archive to stdout
	 * 
	 * @param   string  $filename
	 * @param   bool    $useGzip    Use GZ compression?
	 * @return  string
	 **/
	function toTarOutput($filename,$useGzip)
	{
		if ( !$filename ) {
			return false;
		}

		// Encode processed files into TAR file format
		$this->__generateTar();

		// GZ Compress the data if we need to
		if ( $useGzip ) {
			// Make sure we have gzip support
			if ( !function_exists("gzencode") ) {
				return false;
			}

			$file = gzencode($this->tar_file);
		} else {
			$file = $this->tar_file;
		}

		return $file;
	}
}

?>