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     MM> Does anyone have the structures for RAR archived files?

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     ÛÛÉÍÍÛÛ» ÛÛÉÍÍÛÛ» ÛÛÉÍÍÛÛ»     RAR version 1.53 - Technical information
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     ³THE ARCHIVE FORMAT DESCRIBED BELOW IS ONLY VALID FOR VERSIONS SINCE 1.50³
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     º ±±±±±±±±±±±±±±±±±±±±±±±± RAR archive file format ±±±±±±±±±±±±±±±±±±±±±±º
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       Archive file consists of variable length blocks. The order of these
    blocks may vary, but the first block must be marker block followed by
    an archive header block.

       Each block begins with following fields:

    HEAD_CRC       2 bytes     CRC of total block or block part
    HEAD_TYPE      1 byte      Block type
    HEAD_FLAGS     2 bytes     Block flags
    HEAD_SIZE      2 bytes     Block size
    ADD_SIZE       4 bytes     Optional field - added block size

       Field ADD_SIZE present only if (HEAD_FLAGS & 0x8000) != 0

       Total block size is HEAD_SIZE if (HEAD_FLAGS & 0x8000) == 0
    and HEAD_SIZE+ADD_SIZE if the field ADD_SIZE is present - when
    (HEAD_FLAGS & 0x8000) != 0.

       In each block the followings bits in HEAD_FLAGS have the same meaning:

      0x4000 - if set, older RAR versions will ignore the block
               and remove it when the archive is updated.
               if clear, the block is copied to the new archive
               file when the archive is updated;

      0x8000 - if set, ADD_SIZE field is present and the full block
               size is HEAD_SIZE+ADD_SIZE.

      Declared block types:

    HEAD_TYPE=0x72          marker block
    HEAD_TYPE=0x73          archive header
    HEAD_TYPE=0x74          file header
    HEAD_TYPE=0x75          comment header
    HEAD_TYPE=0x76          extra information

       Comment block is actually used only within other blocks and does not
    exist separately.

       Archive processing is made in the following manner:

    1. Read and check marker block
    2. Read archive header
    3. Read or skip HEAD_SIZE-sizeof(MAIN_HEAD) bytes
    4. If end of archive encountered then terminate archive processing,
       else read 7 bytes into fields HEAD_CRC, HEAD_TYPE, HEAD_FLAGS,
       HEAD_SIZE.
    5. Check HEAD_TYPE.
       In case block read needed:
             if HEAD_TYPE==0x74
               read file header ( first 7 bytes already read )
               read or skip HEAD_SIZE-sizeof(FILE_HEAD) bytes
               read or skip FILE_SIZE bytes
             else
               read corresponding HEAD_TYPE block:
                 read HEAD_SIZE-7 bytes
                 if (HEAD_FLAGS & 0x8000)
                   read ADD_SIZE bytes
       In case block skip needed:
             skip HEAD_SIZE-7 bytes
             if (HEAD_FLAGS & 0x8000)
               skip ADD_SIZE bytes
    6. go to 4.

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     º±±±±±±±±±±±±±±±±±±±±±±±±±±±  Block Formats  ±±±±±±±±±±±±±±±±±±±±±±±±±±±±º
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       Marker block ( MARK_HEAD )

    HEAD_CRC        Always 0x6152
    2 bytes

    HEAD_TYPE       Header type: 0x72
    1 byte

    HEAD_FLAGS      Always 0x1a21
    2 bytes

    HEAD_SIZE       Block size = 0x0007
    2 bytes

       The marker block is actually considered as a fixed byte
    sequence: 0x52 0x61 0x72 0x21 0x1a 0x07 0x00

       Archive header ( MAIN_HEAD )

    HEAD_CRC        CRC of fields HEAD_TYPE to RESERVED2
    2 bytes

    HEAD_TYPE       Header type: 0x73
    1 byte

    HEAD_FLAGS      Bit flags:
    2 bytes
                    0x01    - Volume attribute (archive volume)
                    0x02    - Archive comment present
                    0x04    - Archive lock attribute
                    0x08    - Solid attribute (solid archive)
                    0x10    - Unused
                    0x20    - Authenticity information present

                    other bits in HEAD_FLAGS are reserved for
                    internal use

    HEAD_SIZE       Archive header total size including archive
    2 bytes         comments and other added fields

    RESERVED1       Reserved
    2 bytes

    RESERVED2       Reserved
    4 bytes

    Comment block   present if (HEAD_FLAGS & 0x02) != 0

    ????            Other included blocks - reserved for
                    future use

       File header (File in archive)

    HEAD_CRC        CRC of fields from HEAD_TYPE to FILEATTR
    2 bytes         and file name

    HEAD_TYPE       Header type: 0x74
    1 byte

    HEAD_FLAGS      Bit flags:
    2 bytes
                    0x01 - file continued from previous volume
                    0x02 - file continued in next volume
                    0x04 - file encrypted with password
                    0x08 - file comment present

                    (HEAD_FLAGS & 0x8000) == 1, because full
                    block size is HEAD_SIZE + PACK_SIZE

    HEAD_SIZE       File header full size including file name,
    2 bytes         comments and other added fields

    PACK_SIZE       Compressed file size
    4 bytes

    UNP_SIZE        Uncompressed file size
    4 bytes

    HOST_OS         Operating system used for archiving
    1 byte          (value 0 stands for MS DOS)

    FILE_CRC        File CRC
    4 bytes

    FTIME           Date and time in standard MS DOS format
    4 bytes

    UNP_VER         RAR version needed to extract file
    1 byte

    METHOD          Packing method
    1 byte

    NAME_SIZE       File name size
    2 bytes

    ATTR            File attributes
    4 bytes

    FILE_NAME       File name - string of NAME_LEN bytes size

    Comment block   present if (HEAD_FLAGS & 0x08) != 0

    ????            Other extra included blocks - reserved for
                    future use

      Comment block

    HEAD_CRC        CRC of fields from HEAD_TYPE to COMM_CRC
    2 bytes

    HEAD_TYPE       Header type: 0x75
    1 byte

    HEAD_FLAGS      Bit flags
    2 bytes

    HEAD_SIZE       Comment header size + comment size
    2 bytes

    UNP_SIZE        Uncompressed comment size
    2 bytes

    UNP_VER         RAR version needed to extract comment
    1 byte

    METHOD          Packing method
    1 byte

    COMM_CRC        Comment CRC
    2 bytes

    COMMENT         Comment text

      Extra info block

    HEAD_CRC        Block CRC
    2 bytes

    HEAD_TYPE       Header type: 0x76
    1 byte

    HEAD_FLAGS      Bit flags
    2 bytes

    HEAD_SIZE       Total block size
    2 bytes

    INFO            Other data

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     º±±±±±±±±±±±±±±±±±±±±±±±±±±  Application notes  ±±±±±±±±±±±±±±±±±±±±±±±±±º
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       1. Should fields and included blocks be added in the future, their
    size would be included in HEAD_SIZE.

       2. To process SFX archive you need to skip the SFX module searching
    marker block in the archive. There is no marker block sequence (0x52 0x61
    0x72 0x21 0x1a 0x07 0x00) in the SFX module itself.

       3. The CRC is calculated using the standard polynomial 0xEDB88320. In
    case the size of the CRC is less than 4 bytes, only the low order bytes
    are used.

       4. Packing method encoding:
             0x30 - storing
             0x31 - fastest compression
             0x32 - fast compression
             0x33 - normal compression
             0x34 - good compression
             0x35 - best compression

       5. The RAR extraction version number is encoded as 10 * Major version
    + minor version.

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