Re: [Caml-list] Why is there no Marshal.(from_fd|to_fd)

[Ivan Gotovchits <ivg@ieee.org>]

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Hi,

The main reason is that marshaling is a part of standard library, i.e., the
stdlib.cma, where Unix.file_descr is a part of the unix library, and the
Unix library is not included into the Standard library, thus the latter
cannot depend on the former. So, the only way to introduce such
functionality would be to add Unix.dump_value : file_descr -> 'a -> unit`,
i.e., to the Unix module. It is doable, and I saw such function in
third-party libraries and implemented it myself. There is a small issue
with the buffering, as all file_descr operations are unbuffered and it is
assumed that the do not create any intermediate storages. But the only way
to implement the dump_value function is to use an intermediate buffer, that
kind of contradicts the general spirit of the file_descr interface.

Regards,
Ivan Gotovchits

On Tue, Jun 13, 2017 at 11:01 AM, Francois BERENGER <
berenger@bioreg.kyushu-u.ac.jp> wrote:

> Hello,
>
> Sorry for the maybe stupid question.
>
> I mean fd has type Unix.file_descr.
>
> I am just wondering why marshaling has to always go through an in or
> out_channel.
>
> Is it just so that there is not dependency between the Marshal and the
> Unix module?
>
> I am worried about the data copying that might happen because
> of the channel interposed between me and my file.
>
> Regards,
> F.
>
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