[erlang-questions] Re: Blocking NIFs

Mazen Harake <>
Fri Nov 19 21:55:12 CET 2010


Just curious; are you aware of cecho?

https://github.com/mazenharake/cecho

BR,

/Mazen

On 19/11/2010 20:05, Jeff Zellner wrote:
> To clarify a bit:
>
> I'm writing an ncurses interface in NIFs, and using it running with
> -noinput/-noshell. I'm looking to capture actual key presses, not prompted
> input.
>
> I'd like to avoid dealing with a port program or a driver just for the
> single blocking operation I want to do.
>
> On Fri, Nov 19, 2010 at 12:30 PM, Jeff Zellner<>wrote:
>
>> While I have read the erl_nif documentation (that says "Avoid doing lengthy
>> work in NIF calls as that may degrade the responsiveness of the VM. NIFs are
>> called directly by the same scheduler thread that executed the calling
>> Erlang code. The calling scheduler will thus be blocked from doing any other
>> work until the NIF returns.") -- I'm trying to do keyboard input in a NIF.
>>
>> Is this absolutely a bad idea, or is there a way to make it work? I've
>> found that simple example programs, running ~2 processes, one of them
>> blocking on a getch() in a NIF works fine -- unfortunately trying to
>> integrate that blocking NIF call into a larger program with upwards of 10
>> processes seems to not work at all, regardless of how many async threads I
>> use.
>>
>> Can anyone give me some insight into this?  Preferably something other than
>> 'don't use NIFs to do that' -- I will eventually give up if it's just not
>> workable, but I'm not ready to do that yet! :-)
>>
>> Cheers,
>> Jeff
>>



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