RAR version 3.60 - Technical information               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE ARCHIVE FORMAT DESCRIBED BELOW IS ONLY VALID FOR VERSIONS SINCE 1.50 ==========================================================================                         RAR archive file format ==========================================================================   Archive file consists of variable length blocks. The order of theseblocks may vary, but the first block must be a marker block followed byan archive header block.   Each block begins with the following fields:HEAD_CRC       2 bytes     CRC of total block or block partHEAD_TYPE      1 byte      Block typeHEAD_FLAGS     2 bytes     Block flagsHEAD_SIZE      2 bytes     Block sizeADD_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) == 0and 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 blockHEAD_TYPE=0x73          archive headerHEAD_TYPE=0x74          file headerHEAD_TYPE=0x75          old style comment headerHEAD_TYPE=0x76          old style authenticity informationHEAD_TYPE=0x77          old style subblockHEAD_TYPE=0x78          old style recovery recordHEAD_TYPE=0x79          old style authenticity informationHEAD_TYPE=0x7a          subblock   Comment block is actually used only within other blocks and doesn'texist separately.   Archive processing is made in the following manner:1. Read and check marker block2. Read archive header3. Read or skip HEAD_SIZE-sizeof(MAIN_HEAD) bytes4. 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.   if HEAD_TYPE==0x74     read file header ( first 7 bytes already read )     read or skip HEAD_SIZE-sizeof(FILE_HEAD) bytes     if (HEAD_FLAGS & 0x100)       read or skip HIGH_PACK_SIZE*0x100000000+PACK_SIZE bytes     else       read or skip PACK_SIZE bytes   else     read corresponding HEAD_TYPE block:       read HEAD_SIZE-7 bytes       if (HEAD_FLAGS & 0x8000)         read ADD_SIZE bytes6. go to 4. ==========================================================================                               Block Formats ==========================================================================   Marker block ( MARK_HEAD )HEAD_CRC        Always 0x61522 bytesHEAD_TYPE       Header type: 0x721 byteHEAD_FLAGS      Always 0x1a212 bytesHEAD_SIZE       Block size = 0x00072 bytes   The marker block is actually considered as a fixed bytesequence: 0x52 0x61 0x72 0x21 0x1a 0x07 0x00   Archive header ( MAIN_HEAD )HEAD_CRC        CRC of fields HEAD_TYPE to RESERVED22 bytesHEAD_TYPE       Header type: 0x731 byteHEAD_FLAGS      Bit flags:2 bytes                0x0001  - Volume attribute (archive volume)                0x0002  - Archive comment present                          RAR 3.x uses the separate comment block                          and does not set this flag.                0x0004  - Archive lock attribute                0x0008  - Solid attribute (solid archive)                0x0010  - New volume naming scheme ('volname.partN.rar')                0x0020  - Authenticity information present                          RAR 3.x does not set this flag.                0x0040  - Recovery record present                0x0080  - Block headers are encrypted                0x0100  - First volume (set only by RAR 3.0 and later)                other bits in HEAD_FLAGS are reserved for                internal useHEAD_SIZE       Archive header total size including archive comments2 bytesRESERVED1       Reserved2 bytesRESERVED2       Reserved4 bytes   File header (File in archive)HEAD_CRC        CRC of fields from HEAD_TYPE to FILEATTR2 bytes         and file nameHEAD_TYPE       Header type: 0x741 byteHEAD_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                       RAR 3.x uses the separate comment block                       and does not set this flag.                0x10 - information from previous files is used (solid flag)                       (for RAR 2.0 and later)                bits 7 6 5 (for RAR 2.0 and later)                     0 0 0    - dictionary size   64 KB                     0 0 1    - dictionary size  128 KB                     0 1 0    - dictionary size  256 KB                     0 1 1    - dictionary size  512 KB                     1 0 0    - dictionary size 1024 KB                     1 0 1    - dictionary size 2048 KB                     1 1 0    - dictionary size 4096 KB                     1 1 1    - file is directory               0x100 - HIGH_PACK_SIZE and HIGH_UNP_SIZE fields                       are present. These fields are used to archive                       only very large files (larger than 2Gb),                       for smaller files these fields are absent.               0x200 - FILE_NAME contains both usual and encoded                       Unicode name separated by zero. In this case                       NAME_SIZE field is equal to the length                       of usual name plus encoded Unicode name plus 1.                       If this flag is present, but FILE_NAME does not                       contain zero bytes, it means that file name                       is encoded using UTF-8.               0x400 - the header contains additional 8 bytes                       after the file name, which are required to                       increase encryption security (so called 'salt').               0x800 - Version flag. It is an old file version,                       a version number is appended to file name as ';n'.              0x1000 - Extended time field present.              0x8000 - this bit always is set, so the complete                       block size is HEAD_SIZE + PACK_SIZE                       (and plus HIGH_PACK_SIZE, if bit 0x100 is set)HEAD_SIZE       File header full size including file name and comments2 bytesPACK_SIZE       Compressed file size4 bytesUNP_SIZE        Uncompressed file size4 bytesHOST_OS         Operating system used for archiving1 byte                 0 - MS DOS                       1 - OS/2                       2 - Win32                       3 - Unix                       4 - Mac OS                       5 - BeOSFILE_CRC        File CRC4 bytesFTIME           Date and time in standard MS DOS format4 bytesUNP_VER         RAR version needed to extract file1 byte                Version number is encoded as                10 * Major version + minor version.METHOD          Packing method1 byte                0x30 - storing                0x31 - fastest compression                0x32 - fast compression                0x33 - normal compression                0x34 - good compression                0x35 - best compressionNAME_SIZE       File name size2 bytesATTR            File attributes4 bytesHIGH_PACK_SIZE  High 4 bytes of 64 bit value of compressed file size.4 bytes         Optional value, presents only if bit 0x100 in HEAD_FLAGS                is set.HIGH_UNP_SIZE   High 4 bytes of 64 bit value of uncompressed file size.4 bytes         Optional value, presents only if bit 0x100 in HEAD_FLAGS                is set.FILE_NAME       File name - string of NAME_SIZE bytes sizeSALT            present if (HEAD_FLAGS & 0x400) != 08 bytesEXT_TIME        present if (HEAD_FLAGS & 0x1000) != 0variable sizeother new fields may appear here. ==========================================================================                              Application notes ==========================================================================   1. To process an SFX archive you need to skip the SFX module searchingfor the marker block in the archive. There is no marker block sequence (0x520x61 0x72 0x21 0x1a 0x07 0x00) in the SFX module itself.   2. The CRC is calculated using the standard polynomial 0xEDB88320. Incase the size of the CRC is less than 4 bytes, only the low order bytesare used.