support dumping tapes without tape markers

[ams]

Would be nice if RTAPE could dump tapes without tape markers.

AFAIK, they are not needed if you are dumping over Chaosnet (.tap might be a different story).

[bictorv]

Please elaborate - I don't understand the issue(s)?

[eswenson1]

Yeah. Me too. What value would removing the tape marks have? Seems better that it write tape marks, making the resulting “file” readable with tape tools that expect marks.

[ams]

It just makes it much easier to handle when trying to extract LMFL dumps, it makes the format much easier to process using any random hacks as well.

[eswenson1]

If you’re using emacs to extract files from dumps, sure. But who would be silly enough to do that? :-) Wouldn’t it be better to simply write a real tape file extract too for those tapes?

[ams]

I'd need to write tape mark code for C and Lisp, and possibly shell. But ok, I'll just make a local hack ...

[bictorv]

There are tools for extracting LMFL tapes already: you sent me one, and Lars did too (in an email conversation from February this year).

[ams]

There are sadly multiple formats of LMFL -- and sometimes I have tapes without markers. :-). And the ones that I sent don't do the work I need them to (modification of LMFL headers .. and other nonsense)

@larsbrinkhoff What did you send?

[eswenson1]

I’d like a copy of said tool. The one I have doesn’t work on many LMFL tapes I’ve tried.

[bictorv]

Look in larsbrinkhoff pdp10-its-disassembler, some branch.

[ams]

It is on the lars/lmfl-dump branch -- and this is very much incomplete (even more incomplete than my garbage :-) )

[larsbrinkhoff]

I'm not sure what "tape markers" means here. Usually a "tape mark" is a distinct pattern on the tape which separates records/blocks into "files". Two marks in a row is the logical end of tape.

But I suppose you mean the SIMH tape format fields which frame records in a tape image file; they also describe some other metadata like errors. I suppose it's not overly cumbersome to support various types of tape image formats, one which could be this "marker-less" type. On the other hand, it's quite trivial to "unblock" (as it's sometimes called) a tape (physical or image) to a linear file.

[larsbrinkhoff]

Yes, my LMFL extraction tool is very crude. Possibly only good enough to list some ToTS tapes. (There are more than just PDP-10 tapes there, you know.)

[bictorv]

On the other hand, it's quite trivial to "unblock" (as it's sometimes called) a tape (physical or image) to a linear file.

Probably around 10 lines of code in a suitable high-level language?