I was working on adding the tar streaming functionality we talked about at the developer meeting to pg_basebackup, and rapidly ran across the issue that Andres has been complaining about for a while. The code in receivelog.c just passes an insane number of parameters around. Adding or changing even a small thing ends up touching a huge number of places.
Other than the lack of comments on the fields in StreamCtl to indicate their functions I think this looks good.
I didn't find any mistakes, but I do admit my eyes started glazing over after a bit.
I'd rather not have StreamCtl as a typedef of an anonymous struct if it's exposed in a header though. It should have a name that can be used in forward declarations etc.
After recently working with the XLogReader I can't emphasise enough how important *useful* comments on the fields in these sorts of structs are - the XLogReaderState has ReadRecPtr, readSegNo + readOff + readLen, currRecPtr AND latestPagePtr. Which actually do have comments, just not super helpful ones.
