How do torrent priorities work in Transmission?

Question

C++ / C#

As far as I understand, a separate thread (thread) is created for each piece of the uploaded file, and each piece has a priority - high, low or medium. Accordingly, a piece with a higher priority is loaded faster than a piece with a low one. I'm interested in how this is implemented: perhaps the speed for each download thread is limited according to priority; and perhaps the total number of connections is limited, and threads queue for free slots (abstraction) in accordance with their priorities.
Also, if it's not difficult, tell me where to look for the implementation of priorities in the libtransmission sources.
Thanks in advance!