ssl/NPN: factor out encoding of the protocol list

    ffi::SSL_TLSEXT_ERR_OK

}

/// Convert a set of byte slices into a series of byte strings encoded for SSL. Encoding is a byte

/// containing the length followed by the string.

#[cfg(feature = "npn")]

fn ssl_encode_byte_strings(strings: &[&[u8]]) -> Vec<u8>

{

    let mut enc = Vec::new();

    for string in strings {

        let len = string.len() as u8;

        if len as usize != string.len() {

            // If the item does not fit, discard it

            continue;

        }

        enc.push(len);

        enc.extend(string[..len as usize].to_vec());

    }

    enc

}

/// The signature of functions that can be used to manually verify certificates

pub type VerifyCallback = fn(preverify_ok: bool,

                             x509_ctx: &X509StoreContext) -> bool;

    pub fn set_npn_protocols(&mut self, protocols: &[&[u8]]) {

        // Firstly, convert the list of protocols to a byte-array that can be passed to OpenSSL

        // APIs -- a list of length-prefixed strings.

        let mut npn_protocols = Vec::new();

        for protocol in protocols {

            let len = protocol.len() as u8;

            npn_protocols.push(len);

            // If the length is greater than the max `u8`, this truncates the protocol name.

            npn_protocols.extend(protocol[..len as usize].to_vec());

        }

        let protocols: Box<Vec<u8>> = Box::new(npn_protocols);

        let protocols: Box<Vec<u8>> = Box::new(ssl_encode_byte_strings(protocols));

        unsafe {

            // Attach the protocol list to the OpenSSL context structure,