[asterisk-dev] RTP Bridging optimization

[Vadim Lebedev]

Kevin P. Fleming wrote:

>Vadim Lebedev wrote:
>
>  
>
>>You're right but  only in  the case that when you have separtae briding
>>threads for each direction.
>>I was thinkin about situation when there is ONE briging theard for two
>>directions. The you can you the same pipe
>>for both direction.
>>    
>>
>
>No, you cannot. How are you going to distinguish packets that belong to
>the A->B direction from the ones that belong to the B->A direction if
>both of them are being written to the 'write' end of the same pipe?
>
>Instead of just proposing this idea without fully understanding how it
>would work (here on the developer mailing list), it would be much better
>if you wrote a small program demonstrating the technique and proving
>that it is possible. Otherwise this is all just speculation and people
>disagreeing about what may or may not work.
>
>Certainly it is not at all possible to create a single pipe and using it
>for both directions of multiple bridges... I don't know how you came to
>the conclusion that could work at all.
>  
>

Ok, i'll write a demo program this week....
But the basic approach is trivial:

     FD_SET(&readset, source_fd);
     FD_SET(&readset, target_fd);
    N =  1 + max(source_fd, target_fd);

     select(N, &readset, 0,  0,   &timeout);
   
     if (FD_ISSET(&readset, source_fd))
    {
        // copy from source to target
         slice(source_fd, mypipe[0], .....);
         slice(mypipe[1], target_fd);
    }
    else  if (FD_ISSET(&readset, target_fd))
    {
       // copy from target to source
         slice(target_fd, mypipe[0], .....);
         slice(mypipe[1], source_fd);
    }


The trick is that the pipe is ALWAYS empty.... And when we push 
something to the pipe, we pull the data from it immideately afterwards.
 

Thanks
Vadim

 

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