whicharc.doc

国外网站上的一些精典的C程序

================ whicharc.doc =====================================

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   Modules:    ARCHIVE.CPP, WHICHARC.CPP
   Subject:    tries to determine the archiver used to compress files
   Author:     Heinz Ozwirk
               free for all participants of the C_ECHO
   Started:    28.09.1991   13:35:57
   Modified:   13.10.1991   14:15:57
   Modified:    5 January, 1992 11:50am by David Gersic
                   Added return codes for self  extracting archive files.
   Modified:   16 January, 1992, 4:15pm by David Gersic
                   Added Pak and ARC ver. 6 with information from Richard
                   Vanhouten @1:272/38. I'm not sure that this code works
                   perfectly for those formats, as his message seems to
                   indicate that the entire archive has to be scanned for
                   headers to check before the type can be perfectly
                   determined. It seems to work for test archives produced
                   here, but may not work for all archives.
   Modified:   02 September, 1994 by Jari Laaksonen (2:221/360.20)
                   - partially rewritten, archive types are now C++ classes
                   - added checking of some newer archivers (I'm not sure
                     about the offsets for some SFX archives, but it is
                     now easy to add new archive types).
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   Prototype:  int WhichArc (char *pName)
      pName    address of full path name of file to examine
      Result   -1:      file not found
               UNKNOWN: unknown packer
               ARC:     ARC or PKARC
               ARC6:    ARC ver. 6 or higher
               PAK:     Pak
               HPK:     Hpack
               ZOO:     Zoo
               ARJ:     ARJ
               RAR:     RAR
               UC2:     UC2
               SQZ:     SQZ
               LHA:     LHA
               LHARC:   LHARC
               ZIP1:    PKZIP 1.1x
               ZIP2:    PKZIP 2.xx
               SFXARC:  Self Extracting PKARC
               SFXARC6: Self Extracting ARC ver. 6 or higher
               SFXPAK:  Self Extracting Pak
               SFXARJ:  Self Extracting ARJ
               SFXLHARC:Self Extracting LHARC
               SFXLHA:  Self Extracting LHA
               SFXZIP1: Self Extracting ZIP 1.1x
               SFXZIP2: Self Extracting ZIP 2.xx
               EXE:     MS DOS executable of unknown type

   LHARC/LHA
      No archive header. WhichArc examines the checksum of the first
      file header. If the checksum is valid and if the string -lh?-
      is found, LHA or LHARC is assumed.
      SFX offsets: LHARC         0x653
                   LHA v.???     0x799
                   LHA v.2.10    0x665
                   LHA v.2.12->  0x664

   ARJ
      If a file starts with 0x60, 0xEA, ARJ is assumed.
      SFX offsets: ->ARJ 2.22    0x39BA
                     ARJ 2.41    0x4F4

   ZIP1
      If the file begins with "PK\x03\x04\x0A", PKZIP 1.1x is assumed.
      SFX offsets: PkZip 1.1x    0x31F0

   ZIP2
      If the file begins with "PK\x03\x04\x14", PKZIP 2.xx is assumed.
      SFX offsets: PkZip 2.04c   0x3CCB
                   PkZip 2.04g   0x3D9A
                   PkZip SFXJr   0xBBA

   ZOO
      Zoo'ed archives always start with "ZOO x.xx Archive". WhichArc
      only looks for "ZOO".

   ARC
      No header. Files starting with 0x1A are assumed to be ARCed.
      SFX offsets:               0x261E

   ARC6
      Similar to ARC, but if the second byte of the header is 0x14 or
      higher, it was created by Arc version 6 or higher.
      SFX offsets:               0x261E

   PAK
      Similar to ARC files, but if the second byte of the header is 0x0a or
      0x0b, it was created by Pak.
      SFX offsets:               0x1AD3

   SFX*
      All of the SFX files start with a small decompressor. Seek past
      the decompressor and repeat the above checks.
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