[Tcl-bugs] [ tcl-Bugs-780533 ] [fcopy] callback sometimes fails to trigger

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Bugs item #780533, was opened at 2003-07-30 18:45
Message generated for change (Settings changed) made by msofer
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: miguel sofer (msofer)
>Assigned to: Don Porter (dgp)
Summary: [fcopy] callback sometimes fails to trigger

Initial Comment:
Assigned to dgp for review, as it might have something
to do with [Bug 218203]).

What I see is: let $s be a socket, $f a normal file,
$nBytes a "large" number (8kB or above seems to trigger
the error with good probability), both channels with
"-translation binary". Then the trouble is that
  fcopy $s $f -size $nBytes -command myCallback
often fails to notice that $nBytes *were* already
written to $f, and hence never calls myCallback.

It might be an off-by-one heisenbug: as I said, it
happens often but not always - and it seems never to
happen if one more byte than promised comes through the
socket.

I attached here a script that produces the error with
good probability; uncommenting line 72 does the "one
more byte" trick. 

The script attached below produces the following
results on RH7.2 (relevant??):
 [mig@mini test2]$ /CVS/tcl_SF_clean/unix/tclsh test.tcl 
 /CVS/tcl_SF_clean/unix/tclsh - 8.5a0
 client: done sending
 server: copying 16384 bytes to tempFile
 client: won't wait anymore ...
 server: [fcopy] wanted 16384, and got 16384
 server: [fcopy] doesn't tell us we are finished, exit
anyway

whereas the correct output (uncommenting line 72) is
 [mig@mini test2]$ /CVS/tcl_SF_clean/unix/tclsh test.tcl 
 /CVS/tcl_SF_clean/unix/tclsh - 8.5a0
 server: copying 16384 bytes to tempFile
 client: done sending
 server: copied  16384 bytes to tempFile.
 server: all done


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