When I transmit a Protobuf message optionally compressed with gzip, can I trust that if the message begins with the gzip magic number (0x1f8b) it is the compressed version?
In other words, is it possible that a Protobuf message will begin with 0x1f8b, so my detection method would fail, therefore I would have to prepend a marker flag to explicitly indicate the compression?
Can a Protobuf message begin with a gzip magic number?
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1 Answers
Hex 1f is binary 11111 which, in protobuf varint/field-header terms, is a single byte integer. The lowest 3 bits of a field-header is the wire type, so this would be wire type 7. But, THERE IS NO WIRE TYPE 7. So: hex 1f is not a valid field header and therefore cannot be the first byte of a valid protobuf message.
So: if you see the gzip magic number, it is definitely not a protobuf message that looks similar.
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