extra.fld

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The following are the known types of zipfile extra fields as of this
writing.  Extra fields are documented in PKWARE's appnote.txt and are
intended to allow for backward- and forward-compatible extensions to
the zipfile format.  Multiple extra-field types may be chained together,
provided that the total length of all extra-field data is less than 64KB.
(In fact, PKWARE requires that the total length of the entire file header,
including timestamp, file attributes, filename, comment, extra field, etc.,
be no more than 64KB.)

Each extra-field type (or subblock) must contain a four-byte header con-
sisting of a two-byte header ID and a two-byte length (little-endian) for
the remaining data in the subblock.  If there are additional subblocks
within the extra field, the header for each one will appear immediately 
following the data for the previous subblock (i.e., with no padding for
alignment).

All integer fields in the descriptions below are in little-endian (Intel)
format unless otherwise specified.  Note that "Short" means two bytes and
"Long" means four bytes, regardless of their native sizes.

Greg Roelofs, 970531

			-------------------------

The current list of Header IDs is as follows (0-31 are reserved by PKWARE):

	  0x0007        AV Info
	  0x0009        OS/2 extended attributes
	  0x000c        PKWARE VAX/VMS
	  0x000d        reserved for Unix
	  0x07c8        Info-ZIP Macintosh
	  0x2605        ZipIt Macintosh
	  0x4341        Acorn/SparkFS (David Pilling)
	  0x4453	Windows NT security descriptor (binary ACL)
	  0x4704        VM/CMS
	  0x470f        MVS
	  0x4b46        FWKCS MD5 (third party, see below)
	  0x4c41        OS/2 access control list (text ACL)
	  0x4d49        Info-ZIP VMS (VAX or Alpha)
	  0x5356        AOS/VS (binary ACL)
	  0x5455        extended timestamp
	  0x5855        Info-ZIP Unix (original; also OS/2, NT, etc.)
	  0x6542        BeOS (BeBox, PowerMac, etc.)
	  0x756e        ASi Unix
	  0x7855        Info-ZIP Unix (new)
	  0xfb4a        SMS/QDOS

The following are detailed descriptions of the known extra-field block types:

	 -OS/2 Extended Attributes Extra Field:
	  ====================================

	  The following is the layout of the OS/2 extended attributes "extra"
	  block.  (Last Revision 960922)

	  Note: all fields stored in Intel low-byte/high-byte order.

	  Local-header version:

	  Value		Size		Description
	  -----		----		-----------
  (OS/2)  0x0009	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  BSize		Long		uncompressed EA data size
	  CType		Short		compression type
	  EACRC		Long		CRC value for uncompressed EA data
	  (var.)	variable	compressed EA data

	  Central-header version:

	  Value		Size		Description
	  -----		----		-----------
  (OS/2)  0x0009	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  BSize		Long		size of uncompressed local EA data

	  The value of CType is interpreted according to the "compression
	  method" section above; i.e., 0 for stored, 8 for deflated, etc.

	  The OS/2 extended attribute structure (FEA2LIST) is compressed and
	  then stored in its entirety within this structure.  There will only
	  ever be one block of data in the variable-length field.


	 -OS/2 Access Control List Extra Field:
	  ====================================

	  The following is the layout of the OS/2 ACL extra block.
	  (Last Revision 960922)

	  Local-header version:

	  Value		Size		Description
	  -----		----		-----------
  (ACL)   0x4c41	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  BSize		Long		uncompressed ACL data size
	  CType		Short		compression type
	  EACRC		Long		CRC value for uncompressed ACL data
	  (var.)	variable	compressed ACL data

	  Central-header version:

	  Value		Size		Description
	  -----		----		-----------
  (ACL)   0x4c41	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  BSize		Long		size of uncompressed local ACL data

	  The value of CType is interpreted according to the "compression
	  method" section above; i.e., 0 for stored, 8 for deflated, etc.

	  The uncompressed ACL data consist of a text header of the form
	  "ACL1:%hX,%hd\n", where the first field is the OS/2 ACCINFO acc_attr
	  member and the second is acc_count, followed by acc_count strings
	  of the form "%s,%hx\n", where the first field is acl_ugname (user
	  group name) and the second acl_access.  This block type will be
	  extended for other operating systems as needed.


	 -Windows NT Security Descriptor Extra Field:
	  ==========================================

	  The following is the layout of the NT Security Descriptor (another
	  type of ACL) extra block.  (Last Revision 960922)

	  Local-header version:

	  Value		Size		Description
	  -----		----		-----------
  (SD)    0x4453	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  BSize		Long		uncompressed SD data size
	  Version	Byte		version of uncompressed SD data format
	  CType		Short		compression type
	  EACRC		Long		CRC value for uncompressed SD data
	  (var.)	variable	compressed SD data

	  Central-header version:

	  Value		Size		Description
	  -----		----		-----------
  (SD)    0x4453	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  BSize		Long		size of uncompressed local SD data
	  Version	Byte		version of uncompressed SD data format

	  The value of CType is interpreted according to the "compression
	  method" section above; i.e., 0 for stored, 8 for deflated, etc.
	  Version specifies how the compressed data are to be interpreted
	  and allows for future expansion of this extra field type.  Currently
	  only version 0 is defined.

	  For version 0, the compressed data are to be interpreted as a single
	  valid Windows NT SECURITY_DESCRIPTOR data structure, in self-relative
	  format.


	 -PKWARE VAX/VMS Extra Field:
	  ==========================

	  The following is the layout of PKWARE's VAX/VMS attributes "extra"
	  block.  (Last Revision 12/17/91)

	  Note: all fields stored in Intel low-byte/high-byte order.

	  Value		Size		Description
	  -----		----		-----------
  (VMS)   0x000c        Short           Tag for this "extra" block type
	  TSize         Short           Total Data Size for this block
	  CRC           Long            32-bit CRC for remainder of the block
	  Tag1          Short           VMS attribute tag value #1
	  Size1         Short           Size of attribute #1, in bytes
	  (var.)        Size1           Attribute #1 data
	  .
	  .
	  .
	  TagN          Short           VMS attribute tage value #N
	  SizeN         Short           Size of attribute #N, in bytes
	  (var.)        SizeN           Attribute #N data

	  Rules:

	  1. There will be one or more of attributes present, which will
	     each be preceded by the above TagX & SizeX values.  These
	     values are identical to the ATR$C_XXXX and ATR$S_XXXX constants
	     which are defined in ATR.H under VMS C.  Neither of these values
	     will ever be zero.

	  2. No word alignment or padding is performed.

	  3. A well-behaved PKZIP/VMS program should never produce more than
	     one sub-block with the same TagX value.  Also, there will never
	     be more than one "extra" block of type 0x000c in a particular
	     directory record.


	 -Info-ZIP VMS Extra Field:
	  ========================

	  The following is the layout of Info-ZIP's VMS attributes extra
	  block for VAX or Alpha AXP.  The local-header and central-header
	  versions are identical.  (Last Revision 960922)

	  Value		Size		Description
	  -----		----		-----------
  (VMS2)  0x4d49	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  ID		Long		block ID
	  Flags		Short		info bytes
	  BSize		Short		uncompressed block size
	  Reserved	Long		(reserved)
	  (var.)	variable	compressed VMS file-attributes block

	  The block ID is one of the following unterminated strings:

		"VFAB"		struct FAB
		"VALL"		struct XABALL
		"VFHC"		struct XABFHC
		"VDAT"		struct XABDAT
		"VRDT"		struct XABRDT
		"VPRO"		struct XABPRO
		"VKEY"		struct XABKEY
		"VMSV"		version (e.g., "V6.1"; truncated at hyphen)
		"VNAM"		reserved

	  The lower three bits of Flags indicate the compression method.  The
	  currently defined methods are:

		0	stored (not compressed)
		1	simple "RLE"
		2	deflated

	  The "RLE" method simply replaces zero-valued bytes with zero-valued
	  bits and non-zero-valued bytes with a "1" bit followed by the byte
	  value.

	  The variable-length compressed data contains only the data corre-
	  sponding to the indicated structure or string.  Typically multiple
	  VMS2 extra fields are present (each with a unique block type).


	 -Info-ZIP Macintosh Extra Field:
	  ==============================

	  The following is the layout of the (old) Info-ZIP resource-fork extra
	  block for Macintosh.  The local-header and central-header versions
	  are identical.  (Last Revision 960922)

	  Value		Size		Description
	  -----		----		-----------
  (Mac)   0x07c8	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  "JLEE"	beLong		extra-field signature
	  FInfo		16 bytes	Macintosh FInfo structure
	  CrDat		beLong		HParamBlockRec fileParam.ioFlCrDat
	  MdDat		beLong		HParamBlockRec fileParam.ioFlMdDat
	  Flags		beLong		info bits
	  DirID		beLong		HParamBlockRec fileParam.ioDirID
	  VolName	28 bytes	volume name (optional)

	  All fields but the first two are in native Macintosh format
	  (big-endian Motorola order, not little-endian Intel).  The least
	  significant bit of Flags is 1 if the file is a data fork, 0 other-
	  wise.  In addition, if this extra field is present, the filename
	  has an extra 'd' or 'r' appended to indicate data fork or resource
	  fork.  The 28-byte VolName field may be omitted.


	 -ZipIt Macintosh Extra Field:
	  ===========================

	  The following is the layout of the ZipIt extra block for Macintosh.
	  The local-header and central-header versions are identical.
	  (Last Revision 970130)

	  Value		Size		Description
	  -----		----		-----------
  (Mac2)  0x2605	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  "ZPIT"	beLong		extra-field signature
	  FnLen		Byte		length of FileName
	  FileName	variable	full Macintosh filename
	  FileType	beLong		four-byte Mac file type string
	  Creator	beLong		four-byte Mac creator string


	 -Acorn SparkFS Extra Field:
	  =========================

	  The following is the layout of David Pilling's SparkFS extra block
	  for Acorn RISC OS.  The local-header and central-header versions are
	  identical.  (Last Revision 960922)

	  Value		Size		Description
	  -----		----		-----------
  (Acorn) 0x4341	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  "ARC0"	Long		extra-field signature
	  LoadAddr	Long		load address or file type
	  ExecAddr	Long		exec address
	  Attr		Long		file permissions
	  Zero		Long		reserved; always zero

	  The following bits of Attr are associated with the given file
	  permissions:

		bit 0		user-writable ('W')
		bit 1		user-readable ('R')
		bit 2		reserved
		bit 3		locked ('L')
		bit 4		publicly writable ('w')
		bit 5		publicly readable ('r')
		bit 6		reserved
		bit 7		reserved


	 -VM/CMS Extra Field:
	  ==================

	  The following is the layout of the file-attributes extra block for
	  VM/CMS.  The local-header and central-header versions are
	  identical.  (Last Revision 960922)

	  Value		Size		Description
	  -----		----		-----------
 (VM/CMS) 0x4704	Short		tag for this extra block type
	  TSize		Short		total data size for this block
	  flData	variable	file attributes data

	  flData is an uncompressed fldata_t struct.


	 -MVS Extra Field:
	  ===============

	  The following is the layout of the file-attributes extra block for
	  MVS.  The local-header and central-header versions are identical.
	  (Last Revision 960922)