pub fn peek_message_type<MessageType: TryFrom<u8>>(
bytes: &[u8],
) -> Result<(MessageType, bool), ParseError>Expand description
Peek at an IGMP header to see what message type is present.
Since IgmpPacket is statically typed with the message type expected, this
type must be known ahead of time before calling parse. If multiple
different types are valid in a given parsing context, and so the caller
cannot know ahead of time which type to use, peek_message_type can be used
to peek at the header first to figure out which static type should be used
in a subsequent call to parse.
Because IGMP reuses the message type field for different semantic
meanings between IGMP v2 and v3, peek_message_type also returns a boolean
indicating if it’s a “long message”, which should direct parsers into parsing
an IGMP v3 message.
Note that peek_message_type only inspects certain fields in the header,
and so peek_message_type succeeding does not guarantee that a subsequent
call to parse will also succeed.