Black Archive File Format
=========================

As used by the Archive program originally by Andrew Black,
http://mdfs.net/Apps/Archivers/Archive.

The format of a Black archive is as follows:
  A version 2 Black archive starts with a 'dummy' header to prevent
  earlier versions from extracting incorrectly:
       Read using INPUT#
        000000 : 00 00          : "" - ie, null string
        000002 : 40 FF xx xx xx : ( filelength-17 ) OR &FF000000
        000007 : 40 00 00 00 00 : dummy load% - set to zero
        00000C : 40 00 00 00 00 : dummy exec% - set to zero
        000011 : xx xx ...      : rest of file starts here

   Repeated for each file:
       Read using INPUT#:
        name$  : 00 nn ...      : Filename, last char...first char
        len%   : 40 hi nn mm lo : length
        load%  : 40 hi nn mm lo : load address
        exec%  : 40 hi nn mm lo : execute address
       Version 2 archives then have:
        attr%  : 40 hi nn mm lo : file attributes
       Read using BGET:
        The bytes of the file

Filenames are in Acorn format, ie '.' directory seperators.

The bottom three bytes of len% is the actual data length occupied within the
archive, even if this data expands to form a larger file. The top byte of
len% is a flag. Current meanings are as follows:
        &00     Stored file
        <>&00   Not a file
        &FF     Ignore this data

Future versions will use this flag to indicate actual file compression
methods.

Archive versions before 2.10 will read a version 2 archive file as a single
entry with the flag set to 'ignore this data'. Archive version 2.10 onwards
can read version 1 archive files and version 2 archive files.