<?
// create a tar archive file 
// for regular files (not links, nor directories,...)
// Standard Archive Format - Standard v7 TAR

// F. Hoerni (http://fhoerni.free.fr/comp/) created this script
// you may use it and modify it without restriction
// please report any bug to fhoerni@free.fr

define("BLOCK_SIZE", "512");

function tar_cf($tarname, $file_list) {
	$output_fh = fopen($tarname, "w");
	if (!$output_fh) return -1;
	$n = 0;
	foreach ($file_list as $file) {
		$tar_part = make_tar_header($file);
		$tar_part .= make_tar_body($file);
		$rc = fwrite($output_fh, $tar_part);
		if (!$rc) return -3;
		$n++;
	}
	fclose($output_fh);
	return $n;
}

// tar_c returns the contents
// (no writing into a file occurs)
function tar_c($file_list) {
	$result = "";
	foreach ($file_list as $file) {
		$result .= make_tar_header($file);
		$result .= make_tar_body($file);
	}
	return $result;
}

function tar_czf($tarname, $file_list) {
	$output_fh = gzopen($tarname, "w9");
	if (!$output_fh) return -1;
	$n = 0;
	foreach ($file_list as $file) {
		$tar_part = make_tar_header($file);
		$tar_part .= make_tar_body($file);
		$rc = gzwrite($output_fh, $tar_part);
		if (!$rc) return -3;
		$n++;
	}
	gzclose($output_fh);
	return $n;
}

function make_tar_header($file) {

	$NAME_FIELD_SIZE = 100;
	$MODE_FIELD_SIZE = 8;
	$UID_FIELD_SIZE = 8;
	$GID_FIELD_SIZE = 8;
	$SIZE_FIELD_SIZE = 12;
	$MTIME_FIELD_SIZE = 12;
	$CHKSUM_FIELD_SIZE = 8;
	$LINKNAME_FIELD_SIZE = 100;
	$MAGIC_FIELD_SIZE = 6;
	//$VERSION_FIELD_SIZE = 2;
	$UNAME_FIELD_SIZE = 32;
	$GNAME_FIELD_SIZE = 32;
	$DEV_FIELD_SIZE = 8;

	$stat = stat($file);
	// filename
	if (strlen($file) >= $NAME_FIELD_SIZE) return FALSE;
	$header = $file;
	$header = str_pad($header, $NAME_FIELD_SIZE, "\0");

	if (!$stat) return FALSE;
	
	// mode
	$mode = decoct($stat['mode']);
	$header .= str_pad($mode, $MODE_FIELD_SIZE-1, "0", STR_PAD_LEFT)."\0";

	// uid
	$uid = decoct($stat['uid']);
	$header .= str_pad($uid, $UID_FIELD_SIZE-1, "0", STR_PAD_LEFT)."\0";
	// gid
	$gid = decoct($stat['gid']);
	$header .= str_pad($gid, $GID_FIELD_SIZE-1, "0", STR_PAD_LEFT)."\0";
	// size
	$size = decoct($stat['size']);
	$header .= str_pad($size, $SIZE_FIELD_SIZE-1, "0", STR_PAD_LEFT)."\0";
	// mtime
	$mtime = decoct($stat['mtime']);
	$header .= str_pad($mtime, $MTIME_FIELD_SIZE-1, "0", STR_PAD_LEFT)."\0";

	// save the part of the header which is before the checksum
	$header_before_checksum = $header;
	$header = "";
	// chksum : zero (will be set later)
	
	// typeflag
	$header .= "0";

	// linkname
	$header .= str_pad("", $LINKNAME_FIELD_SIZE, "\0");
	// magic
	$header .= "ustar  \0";
	// uname
	$header .= str_pad("", $UNAME_FIELD_SIZE, "\0");
	// gname
	$header .= str_pad("", $GNAME_FIELD_SIZE, "\0");
	// devmajor
	$header .= str_pad("", $DEV_FIELD_SIZE, "\0");
	// devminor
	$header .= str_pad("", $DEV_FIELD_SIZE, "\0");
	// prefix : nothing

	$checksum = do_checksum("$header_before_checksum"."        "."$header");
	$checksum = decoct($checksum);
	$checksum = str_pad($checksum, $CHKSUM_FIELD_SIZE-1, "0", STR_PAD_LEFT)."\0";
	$header = $header_before_checksum.$checksum.$header;
	return str_pad($header, BLOCK_SIZE, "\0");
}

function make_tar_body($file) {

	$body = file_get_contents($file);
	$number_of_blocks = floor(strlen($body) / BLOCK_SIZE);
	$number_of_blocks ++;
	$body = str_pad($body, $number_of_blocks*BLOCK_SIZE, "\0");
	return $body;
}

function do_checksum($str) {
	$l = strlen($str);
	$sum = 0;
	for ($i=0; $i<$l; $i++) {
		$sum += ord($str[$i]);
	}
	return $sum;
}

?>