How can you optimize binary pattern matching for parsing variable-length network protocols?

Erlang's bit-syntax lets you decode a protocol header directly in a pattern, including fields whose length depends on an earlier field — a common shape in real network protocols (a length-prefixed payload, for instance).

parse(<<Type:8, Len:16, Payload:Len/binary, Rest/binary>>) ->
    {Type, Payload, Rest}.

A few concrete performance habits matter at scale:

• Match the sub-binary, don't copy it — the Payload:Len/binary pattern above creates a reference into the original binary rather than copying bytes, as long as the binary is large enough to be reference-counted.
• Avoid rebuilding accumulated binaries with <<Acc/binary, New/binary>> in a tight loop — each concatenation can copy the growing accumulator; prefer collecting parts in a list and calling list_to_binary/1 once at the end.
• Use Rest/binary generously to keep unconsumed trailing bytes as a reference rather than slicing them into a new copy prematurely.

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