Zero timeout receive

[John Colvin]

On Saturday, 13 April 2013 at 01:26:16 UTC, James Wirth wrote:
> The discussion:
>
>     
> http://forum.dlang.org/thread/mailman.426.1286264462.858.digitalmars-d@puremagic.com?page=9
>
> implies that:
>    receiveTimeout(dur!"msecs"(0), some-callback-function)
>
> is acceptable - meaning that no blocking occurs.  A simple 
> experiment verifies this - but I hesitate to use "undocumented" 
> features.  Some APIs would interpret the 0 as infinity.
>
> I also fear that placing such a nonblocking recieve into the 
> main event loop of a GUI program would impact performance - it 
> would also be non-generic.  Is there a fast function which 
> returns true just when the "mail box" is non-empty?
>
> Thanks

Make a small test and time it. I personally wouldn't expect to 
see much slowdown from the extra code invoked by receiveTimeout 
compared to the rest of a busy loop.

However, either special casing receiveTimeout for 0 duration or 
introducing a new receiveNoBlock or similar would be good.