[Info-vax] C... the only winning move is not to play...

[VAXman- at SendSpamHere.ORG]

In article <ldjc2s$f1b$1 at dont-email.me>, David Froble <davef at tsoft-inc.com> writes:
>{...snip...}
>
>What I meant was the data is read into an internal I/O buffer, and the 
>desired data record is then moved into a user's pre-defined record 
>buffer.  In a write of the data record, RMS moves it back into the 
>internal I/O buffer, then writes the I/O buffer.
>
>If the data in the I/O buffer is locked, then is should not be stale.

OK.  I reread.  You were talking about the locate and move modes of the RMS
buffers.  Locate mode is only valid using a $GET and it's unavailable when
the record crosses a block boundary, file access is set UPDATE, compressed
records (in the case of indexed files), global buffers have been specified
or multiple streams access the file.



>However, I think I've already mentioned that it's been years since I did 
>anything with RMS, and even then I wasn't deep into the internals, so 
>the above is old conjecture.
>
>I wasn't asking how you got the "before image", and respect your 
>intellectual secrets.
>
>
>>> Then there is writing new data.  And global buffers.  My, you really 
>>> have gotten yourself into a quagmire.
>> 
>> Global buffers, believe it or not, are not treated any differently than the
>> local buffers.
>
>Yeah, after I wrote that, I began to suspect that they might be the 
>same, or even easier than private I/O buffers.
>
>>>> When initially scoped out, the idea was to simply intercept the RMS service
>>>> and copy the data from the FAB or RAB but that's not the *right* way to do
>>>> it.  I won't go into detail here for a number of reasons.  I did, however, 
>>>> do a rather detailed expose' on the inner working at two OpenVMS Bootcamps.
>
>This is what I fail to understand.  As far as I know, neither the FAB 
>nor the RAB have any actual data in them.  They surely have some 
>pointers that could be helpful, but no data.

FAB/RAB maintain pointers to data which is what I meant when saying that you
can't trust the FAB and RAB.

-- 
VAXman- A Bored Certified VMS Kernel Mode Hacker    VAXman(at)TMESIS(dot)ORG

Well I speak to machines with the voice of humanity.