Re: [Caml-list] Unix file descriptors vs. in/out channels

[Edouard Evangelisti <edouard.evangelisti@slcu.cam.ac.uk>]

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​​Dear Paolo and Anders,

Thank you for your messages. I tried to use Paolo's code and the exception
Timeout was raised. I was not able to read char by char without O_NONBLOCK
: the program is just waiting forever for something to read.

I was able to retrieve some data using Unix.in_channel_of_descr, but the
data are not transmitted synchronously, which is required in my case. Thus,
I will probably rewrite this part in C using the same strategy and see if
it works. I cannot understand why this strategy works for HyperTerminal and
not for me with the same material.

Thank you again.

Edouard


2014-08-18 17:10 GMT+01:00 Adrien Nader <adrien@notk.org>:

> Hi,
>
> You cannot safely mix buffered (in/out_channel) and un-buffered
> (file_descr) uses of the same underlying resource.
>
> IIRC an in_channel or out_channel has a buffer in OCaml memory.
> If you close the underlying file_descr of an out_channel with
> functions operating on file desriptors directly, it is possible that
> some data will still be buffered.
> If you read alternatively through file_descr and in_channel, you might
> skip some data if reading with the in_channel reads more than just "n
> chars" (it could read 4K for instance, I'm not completely sure).
>
> As for using in/out_channel_of_descr more than once, I don't know
> offhand: if it creates new buffers each time (likely), it will be an
> issue.
>
> --
> Adrien Nader
>
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-- 
Edouard Evangelisti
Post doctoral Research Associate
Sainsbury Laboratory, Cambridge University (SLCU)
Bateman Street
Cambridge CB2 1LR (United Kingdom)

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