Function peek_input_until_verdict_growing 

pub async fn peek_input_until_verdict_growing<R, O, P>(
    reader: &mut R,
    buffer: &mut Vec<u8>,
    max_len: usize,
    read_chunk: NonZero<usize>,
    timeout: Option<Duration>,
    predicate: P,
) -> Option<O>
where
    R: AsyncRead + Unpin,
    P: Fn(&[u8]) -> PeekVerdict<O>,

Available on crate feature std only.

Fail-fast peek that grows its buffer on demand up to max_len, instead of reading into a fixed caller-provided slice like peek_input_until_verdict_with_options.

Use this for a variable-length prefix (e.g. a TLS ClientHello) so the buffer tracks the bytes actually received rather than being pre-sized to a length the peer declared: memory stays proportional to real input, while max_len still bounds a very large — or lying — peer. Once the buffer reaches max_len without a verdict, peeking stops with no match.

buffer is caller-owned and may already hold an earlier peek (e.g. a record header); a non-empty existing prefix is classified first and preserved for replay. The predicate is never called with an empty slice. The buffer grows in read_chunk-sized steps. Returns the matched value, or None on reject / EOF / timeout / reaching max_len without a match; either way buffer is left holding exactly the peeked bytes.