Zero timeout receive

[James Wirth]

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