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#230 Tcl_(FS)OpenFileChannel and 'rb'
The standard 'fopen()' C function allows the
optional "b" mode specifier alongside "rwa+" to
specify that the file to be opened is binary.
Tcl's Tcl_(FS)OpenFileChannel commands do not
support "b" and throw an error if it is given. It
would be quite easy to parse out the "b" and do call
Tcl_SetChannelOption(NULL, chan, "-
translation", "binary") after the channel is opened.
Should this be added to Tcl?
I don't know enough about generic channels in Tcl
to know if it is possible for that action to fail or
otherwise cause problems (bear in mind that, with
VFS, the channel may not be a file, but could be a
memchan, for example).
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What is the behaviour of 8.3 when using a "b" specifier ?
If it is the same I would consider this a feature request, and
not a bug.
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The behaviour hasn't changed since 8.3, so I guess this
is indeed a feature request. One could even imagine a
hookable mechanism in the future which allowed other
(arbitrary) actions to be taken on open. (Set
the 'encoding' automatically might be nice, then
perhaps 'source' could deal with unicode files).
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This is TIP 183.
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Actually this is a bit different from
TIP 183, which proposes the change
only for [open]. That's simpler to do
than changing for Tcl_FSOpenFileChannel()
since the latter raises questions about
what changes each Tcl_Filesystem's
Tcl_FSOpenFileChannelProc might
have to handle in its "mode" argument.
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Turns out doing this at the
Tcl_FSOpenFileChannel() level
works fine, and spares the VFS
drivers from having to do anything.
Here's the patch.
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I haven't had time to test right now, but the patch itself
looks nice and clean.
It would be good to add a new test which writes some stuff
to a file in binary and then reads it back and check that \r
\n line endings have not been mangled.
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Updated patch contains docs and tests.
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correction.
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Committed for Tcl 8.5a3