Xref: utzoo comp.protocols.appletalk:1118 comp.sys.mac.programmer:3097
Path: utzoo!attcan!uunet!husc6!bloom-beacon!mit-eddie!uw-beaver!fluke!jeff
From: jeff@tc.fluke.COM (Jeff Stearns)
Newsgroups: comp.protocols.appletalk,comp.sys.mac.programmer
Subject: What's the format of an AppleDouble resource file?
Keywords: AppleDouble resource GatorBox Cayman Apple Macintosh file format
Message-ID: <5918@fluke.COM>
Date: 10 Nov 88 00:11:54 GMT
Sender: news@tc.fluke.COM
Organization: John Fluke Mfg. Co., Inc., Everett, WA
Lines: 52

Apple has defined a "standard" way of storing Macintosh files on primitive
UNIX-like computers which don't support the concept of resource forks.

It's called AppleDouble, and it cleaves the Macintosh file into two parts
for storage on UNIX.  The data fork is stored byte-for-byte in one file,
and the resource fork is stored in another.  (The resource fork file is
named "%file".) The %file is always 256 bytes larger than the resource fork
of the Macintosh file istelf.

There's a second standard called AppleSingle, which stores the two forks
in one UNIX file, it apparently includes some header information necessary
to separate the two forks later.

    Now the question:  What's the exact format of those extra 256 bytes
		       of an AppleDouble '%' resource file?
		       And what is the format of an AppleSingle file?

For example:
    Imagine a Microsoft Word file named "My Word File".  The data fork contains
    25088 bytes; the resource fork contains 0 bytes.

    If stored on a UNIX filesystem in AppleDouble format, it would be split
    into two files; the 25088 bytes of the data fork would be stored in
    "My Word File".  No surprises there.
    
    Now the 0-byte resource fork is stored into a file named "%My Word File",
    but this UNIX file contains 256 bytes of magic stuff.  Some bytes are
    obvious strings, but there are plenty of inscruitable numbers.  What do
    those bytes mean?  For your amusement, here's a real-life sample:

0000   0  5 16  7  0  1  0  0 4d 61 63 69 6e 74 6f 73   |  ........Macintos
0010  68 20 20 20 20 20 20 20  0  3  0  0  0  9  0  0   |  h       ........
0020   0 80  0  0  0 40  0  0  0  7  0  0  0 c0  0  0   |  .....@..........
0030   0 10  0  0  0  2  0  0  1  0  0  0  0  0  0  0   |  ................
0040   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
0050   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
0060   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
0070   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
0080  57 44 42 4e 4d 53 57 44  1  0 ff ff  0 7d  0  0   |  WDBNMSWD.....}..
0090   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
00a0   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
00b0   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
00c0  eb  6 65 26 eb  b 67 ec 80  0  0  0  0  0  0  0   |  ..e&..g.........
00d0   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
00e0   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
00f0   0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0   |  ................
-- 
    Jeff Stearns        John Fluke Mfg. Co, Inc.               (206) 356-5064
    jeff@tc.fluke.COM   {uw-beaver,microsoft,sun}!fluke!jeff
						  
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