[Caml-list] Labltk.Fileevent for both r and w

[Caml-list] Labltk.Fileevent for both r and w

[Max Kirillov]

Hello!

I've noted that I cannot set both Fileevent.add_fileinput and
Fileevent.add_fileoutput. A short course to sources showed that is seems
to be true: when you call

Tcl_CreateFileHandler(tcl_filehandle(fd), TCL_READABLE, 
                       FileProc, (ClientData)(Long_val(cbid)));

from the otherlibs/labltk/support/cltkFile.c (camltk_add_file_input),
it removes the handler for writing, according to



       There  may  exist  only one handler for a given file at a given time.
       If Tcl_CreateFileHandler is called when a handler already exists	 for
       fd,  then  the  new callback replaces the information that was previ╜
       ously recorded.

(from Tcl_CreateFileHandler(3))

And vice versa.

This is not very useful on ordinary files and pipes,
but it is on sockets and some devices.

This may be worked around using dup, but it is greatly unconvenient.
Is there an option to enable the coexistence of the handlers? I see it
making one function camltk_{add/remove}_file_io, which
installes some wrapper for the case of two handlers, and then the
wrapper chooses the right handler accordind to the mode. This may be
done either in C code (in function FileProc in the same file) or in
ocaml.

-- 
Max

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Re: [Caml-list] Labltk.Fileevent for both r and w

[Francois Rouaix]

Hi,

I vaguely remember that the problem was a defiency of the early 
versions of Tk (you know, back in the 4.x versions). Of course, it 
would now make sense to have a better interface to the Tcl FileHandler 
API.
We could have a camltk_createfilehandler and camltk_deletefilehandler 
mirroring the Tcl API, allowing for the TCL_READABLE and TCL_WRITEABLE 
flags, with backward compatibility for the old API implemented with the 
new one (e.g. add_file_input would call createhandler with 
TCL_READABLE).
Seems possible.
Anyone has the time to write a patch ;-) ?

--f
François Rouaix


> I've noted that I cannot set both Fileevent.add_fileinput and
> Fileevent.add_fileoutput. A short course to sources showed that is 
> seems
> to be true: when you call
>
> Tcl_CreateFileHandler(tcl_filehandle(fd), TCL_READABLE,
>                        FileProc, (ClientData)(Long_val(cbid)));
>
> from the otherlibs/labltk/support/cltkFile.c (camltk_add_file_input),
> it removes the handler for writing, according to

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