Interesting question! If you find a good approach to do this, wrapping it
in a package is certainly interesting (have you checked that there aren’t
any packages that handle this already?).
I can’t help much with the threading stuff, but regarding your global
variable it should be possible to work around the slowness of that. I don’t
know how, or when, you re-bind readnow, but there are two ways to fix it
depending on the specifics:
1.
You never rebind readnow, just mutate it. Mark it const, and it’s fast. (
const means *impossible to rebind*, not *impossible to mutate*)
2.
You rebind readnow, and Condition() is mutable: Mark it const and mutate
it instead of rebinding.
3.
You rebind readnow and Condition() is immutable: Wrap the Condition in a
mutable type, which you assign to const readnow instead, and then rebind
the field in this mutable type. Something like this:
type ConditionWrapper
c::Condition
end
const readnow = ConditionWrapper(Condition())
# where you update:
readnow.c = Condition(args...)
This all assumes that Condition is an immutable concrete type, and you just
want to switch it out for an instance with other field values. If you
actually need to change the *type* of readnow, all bets are off and this
trick won’t work.
// T
On Friday, January 8, 2016 at 9:28:02 PM UTC+1, Miguel Bazdresch wrote:
Hello,
>
> I'd be grateful if you could take a look at some code and suggest
> improvements.
>
> I'm trying to interact with a long-lived process (gnuplot). This process
> reads commands from its STDIN; after each command is executed, it produces
> output on either its STDOUT or STDERR. It's impossible to predict ahead of
> time which of the two streams will be used.
>
> To simplify my tests, I wrote an "echo server" in C, which reads a
> character from its STDIN and outputs it again over either STDOUT or STDERR.
> The code is here: https://gist.github.com/mbaz/1e242694a9c4f1eca576
>
> Then I wrote a julia program that reads a character from its own STDIN,
> sends it to the C echo server, and then tries to read the server's STDOUT
> and STDERR until it finds a character. The code is here:
> https://gist.github.com/mbaz/bb7e2cbaaecc031b1d88
>
> This code works, but I don't know if it is the best approach. Two specific
> questions I have:
>
> * Is my `popen3()` function necessary? This closed issue seems to suggest
> it's not, but I can't figure out how to accomplish what I need in a more
> simple manner: https://github.com/JuliaLang/julia/issues/11824
>
> * Are global variables required to share data with asynchronous tasks?
> Since global variables are slow, this approach may produce undesired code
> slowdowns.
>
> Thanks,
>
> -- mb
>
