fix getting stuck with a full buffer without a valid frame #41
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Only allowing `erase` up to, not including, the tail pointer means that an entire buffer clearing can never really happen unless the tail is actually past-the-end of the underlying memory area. Allow erases to cover the entire span from head to tail inclusively. On a side note, there doesn't seem to be a good reason to dissallow even erase where `last` is past the tail pointer. So no extra sanitization logic is added for such cases.
hansbinderup
reviewed
May 1, 2024
If for some reason the read buffer got filled with data, but no complete hdlc frame was present, the library would get stuck. This is because the buffer is only ever erased from in the good case scenario. As a very simple workaround, albeit not a great one, just drop the entire buffer if it is not possible to deframe the data it contains _and_ it doesn't have room left for more data. Ideally, the recovery mechanism would only drop bytes until a start byte is spotted to make it more graceful on a buffer containing a partial frame. This is, however, already an edge case (otherwise users of the library should be experiencing these lockups at the moment), and thus it seems reasonable to just go for a harsh but simple workaround.
Emil-Juhl
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hansbinderup
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May 3, 2024
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Tl;dr if one is to fill the entire read-buffer with data, which doesn't contain an entire valid hdlc frame, the library would get completely stuck. Rather than only erasing from the read-buffer upon successful decoding, clear the buffer entirely if it is full and decoding fails.