fix(crowtty): don't panic on 1-byte SerMux frames #117
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Currently, `crowtty` calls `carry[..used].split_at(2)` every time it decodes a COBS-encoded frame SerMux frame, to extract the port component from the frame. However, if we send a zero byte while not currently in a frame, the COBS decoder will interpret it as a frame with a single zero in it. When we call `split_at`, crowtty will panic, because the slice only has one byte in it. Commit 5231001 changed the panic handler to always send a zero *before* writing out the panic message, in order to terminate the current SerMux frame if one is in the process of being sent. However, that zero makes crowtty crash if it is *not* decoding a partial frame. This means that, rather than nicely printing the panic message, crowtty just panics immediately when the board panics. That kinda sucks. This branch fixes this, by changing crowtty to check whether the length of the decoded COBS frame is less than the minimum frame length (the 2-byte port number). Now, if we decode a single-byte zero frame, we'll just ignore it and keep going.
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jamesmunns
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area: tools & build
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Currently,
crowttycallscarry[..used].split_at(2)every time it decodes a COBS-encoded frame SerMux frame, to extract the port component from the frame. However, if we send a zero byte while not currently in a frame, the COBS decoder will interpret it as a frame with a single zero in it. When we callsplit_at, crowtty will panic, because the slice only has one byte in it.Commit 5231001 changed the panic handler to always send a zero before writing out the panic message, in order to terminate the current SerMux frame if one is in the process of being sent. However, that zero makes crowtty crash if it is not decoding a partial frame. This means that, rather than nicely printing the panic message, crowtty just panics immediately when the board panics. That kinda sucks.
This branch fixes this, by changing crowtty to check whether the length of the decoded COBS frame is less than the minimum frame length (the 2-byte port number). Now, if we decode a single-byte zero frame, we'll just ignore it and keep going.