[zeromq-dev] how to hook ZMTP to prepend outputs and trim inputs ?

[Laurent Alebarde]

For trimming an incoming message, the very beginning of in_event looks 
like the right place.
For prepending an outgoing message, I would guess out_event just at the 
beginning of the if (!outsize) block. But I am not sure.

What is the granularity of what is written with out_event / int nbytes = 
write (outpos, outsize); , frame ? message ? several message possible ? 
part of a frame possible ?


Le 17/01/2014 11:40, Laurent Alebarde a écrit :
> Hi Devs,
>
> I am doing some experiments (cf at the end for the goal) and wonder 
> where I could hook the beginning of a message both reading and writing.
>
> What I want to do is prepend an outgoing message and trim an incoming 
> message (for any mechanism looks simpler) when some option is set.
>
> Typically, when the option is set, when a new message is received, I 
> want to be able to store a certain amount of the first bytes in a new 
> mechanism buffer, and skip them. These bytes are experimental and not 
> ZMTP, so I have to skip or trim them to not hurt ZMTP. When a message 
> is sent, I want to initialise the buffer with a copy of what I 
> previously stored before ZMTP write the buffer. If it is outpos, I 
> will do outpos += store_size;
>
> So, the question is where & when I should do that to not hurt ZMTP.
>
> FYI, The aim of this experiment is to manage to achieve CURVE 
> proxying. My investigations and tests so far lead me to prepend the 
> client ID in every message sent to the CURVE worker, and that the 
> worker send back this information.
>
> Cheers,
>
>
> Laurent
>
>
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