extra.fld

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          Central-header version:

          Value         Size        Description
          -----         ----        -----------
  (BeOS)  0x6542        Short       tag for this extra block type ("Be")
          TSize         Short       total data size for this block (5)
          BSize         Long        size of uncompr. local EF block data
          Flags         Byte        info bits

          The least significant bit of Flags in both headers indicates whether
          the LOCAL extra field is uncompressed (and therefore whether CType
          and CRC are omitted):

                bit 0           if set, Attribs is uncompressed (no CType, CRC)
                bits 1-7        reserved; if set, assume error or unknown data

          Currently the only supported compression types are deflated (type 8)
          and stored (type 0); the latter is not used by Info-ZIP's Zip but is
          supported by UnZip.

          Attribs is a BeOS-specific block of data in big-endian format with
          the following structure (if compressed, uncompress it first):

              Value     Size        Description
              -----     ----        -----------
              Name      variable    attribute name (null-terminated string)
              Type      Long        attribute type (32-bit unsigned integer)
              Size      Long Long   data size for this sub-block (64 bits)
              Data      variable    attribute data

          The attribute structure is repeated for every attribute.  The Data
          field may contain anything--text, flags, bitmaps, etc.


         -AtheOS Extra Field:
          ==================

          The following is the layout of the file-attributes extra block for
          AtheOS.  This field is a very close spin-off from the BeOS e.f.
          The only differences are:
           - a new extra field signature
           - numeric field in the attributes data are stored in little-endian
             format ("i386" was initial hardware for AtheOS)
          (Last Revision 20040908)

          Local-header version:

          Value         Size        Description
          -----         ----        -----------
 (AtheOS) 0x7441        Short       tag for this extra block type ("At")
          TSize         Short       total data size for this block
          BSize         Long        uncompressed file attribute data size
          Flags         Byte        info bits
          (CType)       Short       compression type
          (CRC)         Long        CRC value for uncompressed file attribs
          Attribs       variable    file attribute data

          Central-header version:

          Value         Size        Description
          -----         ----        -----------
 (AtheOS) 0x7441        Short       tag for this extra block type ("At")
          TSize         Short       total data size for this block (5)
          BSize         Long        size of uncompr. local EF block data
          Flags         Byte        info bits

          The least significant bit of Flags in both headers indicates whether
          the LOCAL extra field is uncompressed (and therefore whether CType
          and CRC are omitted):

                bit 0           if set, Attribs is uncompressed (no CType, CRC)
                bits 1-7        reserved; if set, assume error or unknown data

          Currently the only supported compression types are deflated (type 8)
          and stored (type 0); the latter is not used by Info-ZIP's Zip but is
          supported by UnZip.

          Attribs is a AtheOS-specific block of data in little-endian format
          with the following structure (if compressed, uncompress it first):

              Value     Size        Description
              -----     ----        -----------
              Name      variable    attribute name (null-terminated string)
              Type      Long        attribute type (32-bit unsigned integer)
              Size      Long Long   data size for this sub-block (64 bits)
              Data      variable    attribute data

          The attribute structure is repeated for every attribute.  The Data
          field may contain anything--text, flags, bitmaps, etc.


         -SMS/QDOS Extra Field:
          ====================

          The following is the layout of the file-attributes extra block for
          SMS/QDOS.  The local-header and central-header versions are identical.
          (Last Revision 19960929)

          Value         Size        Description
          -----         ----        -----------
  (QDOS)  0xfb4a        Short       tag for this extra block type
          TSize         Short       total data size for this block
          LongID        Long        extra-field signature
          (ExtraID)     Long        additional signature/flag bytes
          QDirect       64 bytes    qdirect structure

          LongID may be "QZHD" or "QDOS".  In the latter case, ExtraID will
          be present.  Its first three bytes are "02\0"; the last byte is
          currently undefined.

          QDirect contains the file's uncompressed directory info (qdirect
          struct).  Its elements are in native (big-endian) format:

          d_length      beLong          file length
          d_access      byte            file access type
          d_type        byte            file type
          d_datalen     beLong          data length
          d_reserved    beLong          unused
          d_szname      beShort         size of filename
          d_name        36 bytes        filename
          d_update      beLong          time of last update
          d_refdate     beLong          file version number
          d_backup      beLong          time of last backup (archive date)


         -AOS/VS Extra Field:
          ==================

          The following is the layout of the extra block for Data General
          AOS/VS.  The local-header and central-header versions are identical.
          (Last Revision 19961125)

          Value         Size        Description
          -----         ----        -----------
  (AOSVS) 0x5356        Short       tag for this extra block type ("VS")
          TSize         Short       total data size for this block
          "FCI\0"       Long        extra-field signature
          Version       Byte        version of AOS/VS extra block (10 = 1.0)
          Fstat         variable    fstat packet
          AclBuf        variable    raw ACL data ($MXACL bytes)

          Fstat contains the file's uncompressed fstat packet, which is one of
          the following:

                normal fstat packet             (P_FSTAT struct)
                DIR/CPD fstat packet            (P_FSTAT_DIR struct)
                unit (device) fstat packet      (P_FSTAT_UNIT struct)
                IPC file fstat packet           (P_FSTAT_IPC struct)

          AclBuf contains the raw ACL data; its length is $MXACL.


         -Tandem NSK Extra Field:
          ======================

          The following is the layout of the file-attributes extra block for
          Tandem NSK.  The local-header and central-header versions are
          identical.  (Last Revision 19981221)

          Value         Size        Description
          -----         ----        -----------
  (TA)    0x4154        Short       tag for this extra block type ("TA")
          TSize         Short       total data size for this block (20)
          NSKattrs      20 Bytes    NSK attributes


         -THEOS Extra Field:
          =================

          The following is the layout of the file-attributes extra block for
          Theos.  The local-header and central-header versions are identical.
          (Last Revision 19990206)

          Value         Size        Description
          -----         ----        -----------
  (Theos) 0x6854        Short       'Th' signature
          size          Short       size of extra block
          flags         Byte        reserved for future use
          filesize      Long        file size
          fileorg       Byte        type of file (see below)
          keylen        Short       key length for indexed and keyed files,
                                    data segment size for 16 bits programs
          reclen        Short       record length for indexed,keyed and direct,
                                    text segment size for 16 bits programs
          filegrow      Byte        growing factor for indexed,keyed and direct
          protect       Byte        protections (see below)
          reserved      Short       reserved for future use

            File types
            ==========

            0x80  library (keyed access list of files)
            0x40  directory
            0x10  stream file
            0x08  direct file
            0x04  keyed file
            0x02  indexed file
            0x0e  reserved
            0x01  16 bits real mode program (obsolete)
            0x21  16 bits protected mode program
            0x41  32 bits protected mode program

            Protection codes
            ================

            User protection
            ---------------
            0x01  non readable
            0x02  non writable
            0x04  non executable
            0x08  non erasable

            Other protection
            ----------------
            0x10  non readable
            0x20  non writable
            0x40  non executable Theos before 4.0
            0x40  modified Theos 4.x
            0x80  not hidden


         -THEOS old inofficial Extra Field:
          ================================

          The following is the layout of an inoffical former version of a
          Theos file-attributes extra blocks.  This layout was never published
          and is no longer created. However, UnZip can optionally support it
          when compiling with the option flag OLD_THEOS_EXTRA defined.
          Both the local-header and central-header versions are identical.
          (Last Revision 19990206)

          Value         Size        Description
          -----         ----        -----------
  (THS0)  0x4854        Short       'TH' signature
          size          Short       size of extra block
          flags         Short       reserved for future use
          filesize      Long        file size
          reclen        Short       record length for indexed,keyed and direct,
                                    text segment size for 16 bits programs
          keylen        Short       key length for indexed and keyed files,
                                    data segment size for 16 bits programs
          filegrow      Byte        growing factor for indexed,keyed and direct
          reserved      3 Bytes     reserved for future use


         -FWKCS MD5 Extra Field (0x4b46):
          ==============================

          The FWKCS Contents_Signature System, used in automatically
          identifying files independent of filename, optionally adds
          and uses an extra field to support the rapid creation of
          an enhanced contents_signature.
          There is no local-header version; the following applies
          only to the central header.  (Last Revision 19961207)

          Central-header version:

          Value         Size        Description
          -----         ----        -----------
  (MD5)   0x4b46        Short       tag for this extra block type ("FK")
          TSize         Short       total data size for this block (19)
          "MD5"         3 bytes     extra-field signature
          MD5hash       16 bytes    128-bit MD5 hash of uncompressed data
                                    (low byte first)

          When FWKCS revises a .ZIP file central directory to add
          this extra field for a file, it also replaces the
          central directory entry for that file's uncompressed
          file length with a measured value.

          FWKCS provides an option to strip this extra field, if
          present, from a .ZIP file central directory. In adding
          this extra field, FWKCS preserves .ZIP file Authenticity
          Verification; if stripping this extra field, FWKCS
          preserves all versions of AV through PKZIP version 2.04g.

          FWKCS, and FWKCS Contents_Signature System, are
          trademarks of Frederick W. Kantor.

          (1) R. Rivest, RFC1321.TXT, MIT Laboratory for Computer
              Science and RSA Data Security, Inc., April 1992.
              ll.76-77: "The MD5 algorithm is being placed in the
              public domain for review and possible adoption as a