formats index
	*** CPK

** Document revision 1.1

  This format, created by Andre Fachat, was not designed for the  emulators
specifically, but was made primarily for Andre's own purposes.

  It is a very basic format using simple RLE compression,  with  each  file
following in sequential order (as Andre put it, "its similar to a UNIX  TAR
file"). There is no central directory, none of the files are byte  aligned,
and it uses compression so every file will be different.

      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F        ASCII
      -----------------------------------------------   ----------------
0000: 01 40 41 2E 41 4E 4C 2C 50 00 01 08 24 08 64 00   .@A.ANL,P˙..$.d˙
0010: 99 22 93 20 20 20 41 4E 4C 45 49 54 55 4E 47 20   Ö"ô˙˙˙ANLEITUNG˙
0020: 5A 55 4D 20 40 41 53 53 45 4D 42 4C 45 52 00 4E   ZUM˙@ASSEMBLER˙N
0030: 08 6E 00 99 22 11 40 41 53 53 20 49 53 54 20 45   .n˙Ö".@ASS˙IST˙E
0040: 49 4E 20 32 2D 50 41 53 53 2D 41 53 53 45 4D 42   IN˙2-PASS-ASSEMB
0050: 4C 45 52 2E 20 44 45 52 00 78 08 78 00 99 22 11   LER.˙DER˙x.x˙Ö".

  The first byte of the file is the version byte. Presently,  only  $01  is
supported.

0000: 01 .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..   ................

  The filename  follows,  stored  in  standard  PETASCII,  and  no  padding
characters ($A0) are included.

0000: .. 40 41 2E 41 4E 4C .. .. .. .. .. .. .. .. ..   .@A.ANL.........

  The filetype is attached to the end of the filename in the form of  ',x',
where x is the filetype used (P,S,U), and it is in PETASCII upper case. The
filename ends with a $00 (null terminated). REL files are  *not*  supported
as there is no provision made for the RECORD size byte.

  Note that not *all* CPK files will have the ",x" extension added  on.  If
it doesn't exist, assume that the file is a "PRG" type.

0000: .. .. .. .. .. .. .. 2C 50 00 .. .. .. .. .. ..   .......,P˙......

Following the filename, we get program data.

      00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F        ASCII
      -----------------------------------------------   ----------------
0000: .. .. .. .. .. .. .. .. .. .. 01 08 24 08 64 00   ............$.d˙
0010: 99 22 93 20 20 20 41 4E 4C 45 49 54 55 4E 47 20   Ö"ô˙˙˙ANLEITUNG˙
 ...
0270: 00 83 0A E6 00 99 22 11 20 20 31 32 33 F7 08 20   ˙â˙Š˙Ö".˙˙123¸.˙
0280: 2D 44 45 5A 49 4D 41 4C 00 A4 0A F0 00 99 22 11   -DEZIMAL˙Ą˙­˙Ö".
0290: 20 20 24 33 34 35 F7 07 20 2D 48 45 58 41 44 45   ˙˙$345¸.˙-HEXADE

  The data requires some explanation as it uses RLE (Run  Length  Encoding)
compression. When creating the archives, data in the file to be  compressed
is scanned for runs of repeating bytes, and when a string of 3 or more  (up
to 255) is found, then the following sequence of bytes is output...

  $F7 $xx $yy - where F7 is the code used for "encoded  sequence  follows",
                $xx is the number of times to repeat the byte  and  $yy  is
                the byte to repeat. Using the sample below, we see  the  F7
                code, then a "repeat 7 times the number $20"

0290: .. .. .. .. .. .. F7 07 20 .. .. .. .. .. .. ..   ......¸.˙.......

  Using $F7 as the encoder byte presents one problem: When encoding a file,
and we encounter an $F7, what does the packer do? Simple, it  gets  encoded
into $F7 $xx $F7 meaning repeat $F7 for as many times as is needed (if  its
only 1 $F7, then the value for $xx  is  $01).  The  code  'F7'  was  chosen
because it is not a 6502 opcode, a BASIC token, or any commonly used  byte,
but *not* because it has the least statistical probability of occuring.

  The stored program ends when the string $F7  $00  is  encountered,  since
this sequence can not occur in the file naturally. If you  need  to  search
through a CPK file for the filenames, do a  hex  search  for  all  $F7  $00
sequences, since they preceed all filenames except the first.

  The end of the archive is known two different ways:

    1. When an EOF (end of file) occurs, after an $F7  $00  byte  sequence.
       This is the normal method.
    2. When a filename of $00 occurs, meaning there is no filename, just  a
       null termination. This is not much used anymore.

  Using method #1 for ending the file  is  more  common  because  it  makes
adding files to the archive very easy. All you have to do as append the new
filename/data to the archive. Using method #2 means you have to  check  and
see if the last three characters are $F7 $00 $00, and start writing the new
file into the archive starting after the first $00.

  In order to extract *one* specific file, you would need to read the whole
archive until you find the filename you want, then output that  file  only.
As this format has no central directory and no  file  location  references,
there is no other way to do it.

  This format has not been used for some time now, as when it came out  D64
and T64 were also being developed and  accepted  into  common  use.  It  is
unlikely you will find *any* files in this format.  64COPY  V3.2  (and  up)
does support extraction of these files just in case any are encountered.