modified _add_data() to be compatible with OS X
(removed CRC and length from end of file stream)
diff --git a/system/libraries/Zip.php b/system/libraries/Zip.php
index 377c387..518c978 100644
--- a/system/libraries/Zip.php
+++ b/system/libraries/Zip.php
@@ -156,7 +156,7 @@
 		$crc32	= crc32($data);

 		

 		$gzdata = gzcompress($data);

-		$gzdata = substr(substr($gzdata, 0, strlen($gzdata) - 4), 2); 	

+		$gzdata = substr($gzdata, 2, -4);

 		$newlen = strlen($gzdata);

 	

 		$this->zipdata[] = "\x50\x4b\x03\x04\x14\x00\x00\x00\x08\x00\x00\x00\x00\x00"

@@ -166,10 +166,7 @@
 							.pack('v', strlen($filepath))

 							.pack('v', 0)

 							.$filepath

-							.$gzdata

-							.pack('V', $crc32)

-							.pack('V', $newlen)

-							.pack('V', $oldlen);

+							.$gzdata;

 			

 		$newoffset = strlen(implode("", $this->zipdata));