Add tags without copying samples?

[Thomas Lorblanchès]

Hi all,
I have some custom blocks that do not change the samples but only add tags in 
the output stream.
At very high sampling rates, all these "memcpy" operations to copy the input 
samples to the output stream take a lot of time and put a lot of memory 
pressure on the system, and are completly useless on an algorithmic point of 
view.
Is there a clever way to add tags without copying the samples?
Thanks for your answers.
Thomas