Fix message framing (backtracking parser) #225
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added 4 commits
February 27, 2024 22:03
This allows the parser to backtrack in case a STX byte in the middle of a message is mistaken for the start-of-frame (checked via CRC)
…tation (`PeekReader`)
patrickelectric
approved these changes
Mar 4, 2024
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This PR fixes an issue where the parser can detect a STX byte that's not really a start of frame marker, but a random byte in the middle of a message, and then consume the next (few) real start-of-frame marker(s) as part of the incorrectly identified frame.
This situation can happen upon (re)connection or over lossy connections (e.g. radio) where some bytes are occasionally lost.
Although the parser will most likely resynchronise at some point (not guaranteed), this issue will still cause the loss of messages that have otherwise been correctly received in full.
The solution implemented is to use a buffered/peekable reader that can backtrack once the CRC is found to be incorrect.
In addition, this PR moves the CRC check to
read_vX_message_raw, which ensures that a call to this function will always produce a valid Mavlink frame (raw message).fixes #222