Detailed descriptions of Extra Fields defined by third
party mappings will be documented as information on
these data structures is made available to PKWARE.
PKWARE does not guarantee the accuracy of any published
third party data.
The Data Size field indicates the size of the following
data block. Programs can use this value to skip to the
next header block, passing over any data blocks that are
not of interest.
Note: As stated above, the size of the entire .ZIP file
header, including the file name, comment, and extra
field should not exceed 64K in size.
In case two different programs should appropriate the same
Header ID value, it is strongly recommended that each
program place a unique signature of at least two bytes in
size (and preferably 4 bytes or bigger) at the start of
each data area. Every program should verify that its
unique signature is present, in addition to the Header ID
value being correct, before assuming that it is a block of
known type.
-ZIP64 Extended Information Extra Field (0x0001):
The following is the layout of the ZIP64 extended
information "extra" block. If one of the size or
offset fields in the Local or Central directory
record is too small to hold the required data,
a ZIP64 extended information record is created.
The order of the fields in the ZIP64 extended
information record is fixed, but the fields will
only appear if the corresponding Local or Central
directory record field is set to 0xFFFF or 0xFFFFFFFF.
Note: all fields stored in Intel low-byte/high-byte order.
Value Size Description
----- ---- -----------
(ZIP64) 0x0001 2 bytes Tag for this "extra" block type
Size 2 bytes Size of this "extra" block
Original
Size 8 bytes Original uncompressed file size
Compressed
Size 8 bytes Size of compressed data
Relative Header
Offset 8 bytes Offset of local header record
Disk Start
Number 4 bytes Number of the disk on which
this file starts
This entry in the Local header must include BOTH original
and compressed file sizes.
-OS/2 Extra Field (0x0009):
The following is the layout of the OS/2 attributes "extra"
block. (Last Revision 09/05/95)
Note: all fields stored in Intel low-byte/high-byte order.
Value Size Description
----- ---- -----------
(OS/2) 0x0009 2 bytes Tag for this "extra" block type
TSize 2 bytes Size for the following data block
BSize 4 bytes Uncompressed Block Size
CType 2 bytes Compression type
EACRC 4 bytes CRC value for uncompress block
(var) variable Compressed block
