[9fans] tr2post & Bopen historical mystery

[9fans] tr2post & Bopen historical mystery

[Anthony Sorace]

Here's a pair of small historical mysteries that came up on IRC.

Bopen allows you to open a file OREAD or OWRITE; you cannot open it read+write. That's been true at least since 2nd Edition.

But /sys/src/cmd/postscript/tr2post/picutres.c contains a pair of invocations of "Bopen(pictmpname, ORDWR))" which are masked behind an "#ifdef UNDEF". This is to handle "InlinePicture", which our tr2post doesn't implement. Both the v10 Unix and Heirloom Troff versions of dpost have equivalent functions to handle that which *are* implemented, and while the code is obviously very different, the high-level structure is similar.

So two mysteries:

1) Was "Bopen(foo, ORDWR)" ever something that worked, and this was commented out when that was disabled, or was this a placeholder draft hypothetical port of the old code's function?

2) dpost and tr2post both use this (or would, if tr2post's were implemented) to handle InlinePicture directives from troff (x X InlinePicture name size). tr2post inherits the comment block at the top of dpost, including the comment "Support for in-line pictures is an attempt to address requirements, expressed by several organizations, ...". That implies to me that it was included in Unix by mandate and the Plan 9 folks said "nobody uses or cares about this in practice, we're not going to bother".

I don't know the history of dpost well enough; can anyone say if that was an AT&T org(s) asking for that?


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