Re: [Caml-list] input_line

[Lauri Alanko <la@iki.fi>]

On Tue, Apr 30, 2002 at 02:07:20PM +0200, Xavier Leroy wrote:
> > And worst of all, there are no limits on the size of string
> > to be created. So a maliciously designed huge input could blow either
> > the stack or the heap. I wouldn't want to use input_line in a network
> > application.
> 
> I see your point, but there are other (most?) applications where you
> really do not want to have any hard limits beyond available memory.

Well, strings already _have_ a hard limit on their size...

But on second thought, yes, it seems that networking applications do
need features that are beyond what can reasonably be expected from a
Pervasives function. For example, in addition to limiting memory usage,
I also need to implement timeouts. Since there is no way to
asynchronously interrupt threads[1], the only way to make sure a
thread never blocks indefinitely is to use nonblocking IO, which
complicates things a bit.

So I ended up writing my own IO interface on top of the Unix module.
What bothers me about this is that now I cannot use any library
functions that operate on (in|out)_channels. Moreover, I had to
implement basic buffering, although the channel implementations do that
already.

Why, therefore, is it not possible to create standard channels that are
backed by user-defined functions? This is pretty much a standard feature
in many languages, and it would make life easier in many ways.


Lauri Alanko
la@iki.fi

[1] Or so I gather. The Haskell folks have studied asynchronous
exceptions in PLDI '01 and implemented them in GHC. Perhaps their work
could be adapted for ocaml as well?
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