Function nghttp2_check_method 

pub unsafe extern "C" fn nghttp2_check_method(
    value: *const u8,
    len: usize,
) -> c_int

@function

Returns nonzero if the |value| which is supposed to be the value of the :method header field is valid according to https://datatracker.ietf.org/doc/html/rfc7231#section-4 and https://datatracker.ietf.org/doc/html/rfc7230#section-3.2.6