Post Reply 
HEPAX File System, file names
01-13-2021, 03:34 PM
Post: #1
HEPAX File System, file names
One of my current little projects is to expand my HP41 disassembler with support for the HEPAX RAM images. With the help of Ángel I now have the details of the files structure. What is lacking is how the file names are coded. According to the available documentation 7 characters are compressed in 6 10-bit words. After some attempts I am still pretty much in the dark as to how this is compressed. It appears that two-bit pairs are spread over the 6 available ROM words, but I fail to see any logic in the patterns.
Next task would be to understand how Register Files are compressed, one 7-byte HP41 register is compressed is 6 10-bit ROM words. Most logical would be if the same compression as the filenames are used, but who knows ...
Does anyone here have any detailed info about this?

Regards, Meindert
Find all posts by this user
Quote this message in a reply
01-13-2021, 03:52 PM
Post: #2
RE: HEPAX File System, file names
(01-13-2021 03:34 PM)MeindertKuipers Wrote:  It appears that two-bit pairs are spread over the 6 available ROM words, but I fail to see any logic in the patterns.

Perhaps if you posted several examples of the 60 bit patterns someone could take a crack at decoding them. It would be especially helpful if you knew what strings the 60 bit patterns encoded for, though it might be possible to do it without knowing the plaintext.

I'm not saying I'm likely to get the answers, but it strikes me that the mathematically inclined users of this forum might enjoy the challenge.


Regards,
Howard
Find all posts by this user
Quote this message in a reply
01-13-2021, 04:16 PM (This post was last modified: 01-13-2021 04:18 PM by Ángel Martin.)
Post: #3
RE: HEPAX File System, file names
Here's a couple of examples"
Code:
434        
4D4        
54C    Compressed File Name    
395    "ELEMNT4"    
115    
C11

and:

Code:
254    
0D4    
14C    Compressed File Name
153    "ELEMENT"
115    
011

and:

Code:
420    
494    
045    Compressed File Name
3D1    "PERIOD"
549    
814

and:

Code:
020    
202    
E4D    Compressed File Name
808    "NM"
480    
813

"To live or die by your own sword one must first learn to wield it aptly."
Find all posts by this user
Quote this message in a reply
01-13-2021, 05:03 PM
Post: #4
RE: HEPAX File System, file names
I am making some progress, changing the filename in a structured way and monitoring the changes.

Regards, Meindert
Find all posts by this user
Quote this message in a reply
01-13-2021, 05:07 PM (This post was last modified: 01-13-2021 05:19 PM by Sylvain Cote.)
Post: #5
RE: HEPAX File System, file names
// HEPAX is padding the filename with spaces
Code:
0x20202020202020 -> [8092] 020 202 020 008 080 008  <-  CLA  32 XTOA 20 HCRFLD [memory dump] HPURFL
Code:
0x01202020202020 -> [8092] 020 202 120 008 080 000  <-  CLA   1 XTOA 20 HCRFLD [memory dump] HPURFL
0x02202020202020 -> [8092] 020 202 220 008 080 000  <-  CLA   2 XTOA 20 HCRFLD [memory dump] HPURFL
0x03202020202020 -> [8092] 020 202 320 008 080 000  <-  CLA   3 XTOA 20 HCRFLD [memory dump] HPURFL
0x04202020202020 -> [8092] 020 202 020 008 080 001  <-  CLA   4 XTOA 20 HCRFLD [memory dump] HPURFL
0x07202020202020 -> [8092] 020 202 320 008 080 001  <-  CLA   7 XTOA 20 HCRFLD [memory dump] HPURFL
0x08202020202020 -> [8092] 020 202 020 008 080 002  <-  CLA   8 XTOA 20 HCRFLD [memory dump] HPURFL
  ˆˆ                               ˆ            ˆˆ
Code:
0x0F202020202020 -> [8092] 020 202 320 008 080 003  <-  CLA  15 XTOA 20 HCRFLD [memory dump] HPURFL
0x10202020202020 -> [8092] 020 202 020 008 080 004  <-  CLA  16 XTOA 20 HCRFLD [memory dump] HPURFL
0x7F202020202020 -> [8092] 020 202 320 008 080 01F  <-  CLA 127 XTOA 20 HCRFLD [memory dump] HPURFL
0x80202020202020 -> [8092] 020 202 020 008 080 020  <-  CLA 128 XTOA 20 HCRFLD [memory dump] HPURFL
0xFF202020202020 -> [8092] 020 202 320 008 080 03F  <-  CLA 255 XTOA 20 HCRFLD [memory dump] HPURFL
  ˆˆ                               ˆ            ˆˆ
Code:
0xFF012020202020 -> [8092] 020 202 301 008 080 03F  <-  CLA 255 XTOA  01 XTOA 20 HCRFLD [memory dump] HPURFL
0xFFFF2020202020 -> [8092] 020 202 3FF 008 080 03F  <-  CLA 255 XTOA 255 XTOA 20 HCRFLD [memory dump] HPURFL
    ˆˆ                              ˆˆ
I will let you complete the test ...

edit 1: [memory dump] = HEXEDIT 8092 SST SST SST SST SST SST ← ←
edit 2: my tests assumed an empty HEPAX RAM at the start
Find all posts by this user
Quote this message in a reply
01-13-2021, 07:13 PM
Post: #6
RE: HEPAX File System, file names
Thanks for your support, I figured it out. Just a lot of tedious typing and checking to find out. I still need to verify if this works in my disassembler, but here it is (only one file assumed in HEPAX RAM):

Code:

              bit in word  
              9-8   7-6    5-4    3-2    1-0
   [C092]     t24   t25    t26    t27    t28
   [C093]     t14   t15    t16    t17    t18
   [C094]     t4    t5     t6     t7     t8
   [C095]     t19   t20    t21    t22    t23
   [C096]     t9    t10    t11    t12    t13
   [C097]     -     -      t1     t2     t3
   
   If the filename is (assuming a 7-character filename):
   t1.t2.t3.t4 / t5.t6.t7.t8 / t9.t10.t11.t12 / t13.t14.t15.t16 / t17.t18.t19.t20 / t21.t22.t23.t24 / t25.t26.t27.t28

where txx is always a pair of bits (2 bits)

The filename seems to be delimited with a <space> (when shorter than 7 characters), a non assigned file (the first empty in the system) seems to have a name of all spaces.

It is not entirely logical to me, so it would be nice if somehow the background of this choice of coding could ever be available. Now work to verify this en then check if this also applies to the packing of a register in 6 10-bit words.

Strange enough, it is possible to rename a HEPAX file to a name with only one space, or to have a filename with spaces between character, so the delimiting space is not very strict.

Regards, Meindert
Find all posts by this user
Quote this message in a reply
01-14-2021, 02:07 AM (This post was last modified: 01-14-2021 02:43 AM by Diego Diaz.)
Post: #7
RE: HEPAX File System, file names
Hi all,

Assumed single program file, seven chr. filename (eg. "ABCDEFG") Chr1="G", Chr7="A".

Taken from the notes and test I did several years ago, I have not double checked this again.

Indeed it's anything but "intuitive", and certainly not easy to figure out.

Code:

8091: Chr2 b1,b0; Chr1 b7-b0.
8092: Chr4 b5-b0; Chr3 b7-b4.
8093: Chr7 b1,b0; Chr6 b7-b0.
8094: Chr3 b3-b0; Chr2 b7-b2.
8095: Chr5 b7-b0; Chr4 b7,b6.
8096: Void b9-b6; Chr7 b7,b2.

Hope this helps.

Best from Caribbean.

Diego

EDIT: I've now realized that there is some 'logic' in this encoding method.
The filename is inserted (bitwise) following the sequence: 8091, 8094, 8092, 8095, 8093, 8096. LSB -> MSB.

"Do not suppose, check it twice."
Find all posts by this user
Quote this message in a reply
01-17-2021, 11:28 AM
Post: #8
RE: HEPAX File System, file names
This HEPAX compression format is now confirmed, and is also valid for the packed registers (DA, WA and KE file types). It is real fun to dive this deep in the HEPAX file structure, respect to the makers of HEPAX!

Next task is to clean up some things in the disassembly listings and add support for multi-block files. Below is a sneak preview of a disassembled HEPAX ASCII file. I intend to make the listing a bit more text focused for readability, and indicate <EOL> and <EOF> plus the record pointer. The ASCII files are not compressed.

Code:

_HPX_FL03   A460 003          .HEPAX      003                         ; type = AS   ASCII
_HPX_NM03   A461 020 145 153  .HEPAX      "ASCTST "                   ; FileName "020 145 153 0D5 10D 010 091"
_HPX_SZ03   A467 091 000      .HEPAX      0091                        ; HEPAX Filesize 140 words / 20.0 regs
_HPX_BS03   A469 010 000      .HEPAX      0010                        ; HEPAX words in this block 11
_HPX_PT03   A46B 000 000      .HEPAX      0000                        ; HEPAX Filepointer 
_HPX_CH03   A46D 00F          .HEPAX      00F                         ; HEPAX char pointer (ASCII files)

_HEP_ASC03  A46E              .L000       00F 054 045 053 054 020 041 ; . T E S T   A 
            A475              .L001       04C 050 048 041 020 044 041 ; L P H A   D A 
            A47C              .L002       054 041 0FF 002 064 000 000 ; T A . . d . . 
            A483              .L003       000 126 314 150 056 000 000 ; . & . P V . . 
            A48A              .L004       126 314 150 056 000 000 000 ; & . P V . . . 
            A491              .L005       200 000 000 000 000 000 300 ; . . . . . . . 
            A498              .L006       000 000 000 000 000 000 000 ; . . . . . . . 
            A49F              .L007       000 000 000 000 000 000 000 ; . . . . . . . 
            A4A6              .L008       000 000 000 000 000 000 000 ; . . . . . . . 
            A4AD              .L009       000 000 000 000 000 000 000 ; . . . . . . . 
            A4B4              .L010       000 000 000 000 000 000 000 ; . . . . . . . 
            A4BB              .L011       000 000 000 000 001 000 100 ; . . . . . . . 
            A4C2              .L012       000 000 000 000 000 000 000 ; . . . . . . . 
            A4C9              .L013       000 000 000 000 000 000 000 ; . . . . . . . 
            A4D0              .L014       000 000 000 000 000 000 000 ; . . . . . . . 
            A4D7              .L015       000 000 000 000 000 000 000 ; . . . . . . . 
            A4DE              .L016       000 000 000 000 000 000 000 ; . . . . . . . 
            A4E5              .L017       000 000 000 000 000 000 000 ; . . . . . . . 
            A4EC              .L018       000 000 000 000 000 000 000 ; . . . . . . . 
            A4F3              .L019       000 000 000 000 000 000 000 ; . . . . . . .

Regards, Meindert
Find all posts by this user
Quote this message in a reply
01-18-2021, 08:54 PM
Post: #9
RE: HEPAX File System, file names
Thank you for the kind words. Interesting that you are making a disassembler for the HEPAX RAM - cool!

I do not remember how the file names were compressed, but as I had a tendency to reuse existing code, then the encoding and decoding must be something I called in a sub-routine. I for sure could never think of a coding like that.

In one of the other threads there was a reference to a presentation I made in Corvallis in 1988 about the HEPAX File System - I have attached it here for your reference.

Keep up the good work with the HEPAX RAM disassembler!

Best regards,
Steen


Attached File(s)
.pdf  HHCU Conference 1988 - The HEPAX File System.pdf (Size: 1.07 MB / Downloads: 23)
Find all posts by this user
Quote this message in a reply
01-19-2021, 06:06 PM
Post: #10
RE: HEPAX File System, file names
Thank you Steen,

It is really good to have you here in the forum and getting the dust of your old stuff. I did have access to your presentation, and it was really helpful. I now need to understand how multi-block files are linked in detail. I never had a real HEPAX, but today have 4 different platforms for testing, although now my DM41X is slightly favourite.

Regards, Meindert
Find all posts by this user
Quote this message in a reply
Post Reply 




User(s) browsing this thread: