Function parse_client_hello_message_prefix 

pub fn parse_client_hello_message_prefix(i: &[u8]) -> ClientHelloHandshakePrefix

Available on crate feature tls only.

Incrementally classify a (possibly partial) bare TLS ClientHello handshake message: the handshake header and body with no TLS record layer in front, as QUIC carries in its CRYPTO stream (RFC 9001 §4.1).

The record-framed counterpart is parse_client_hello_handshake_prefix; this one skips the record header a QUIC CRYPTO stream never has. Same incompleteness contract: Incomplete while the buffered bytes are a valid but unfinished prefix, Invalid when they can never complete.