int writeDirectByteBuffer(long sourceAddress, int sourceLength) throws IOException {
        lock.readLock().lock();
        try {
            return NativeCrypto.ENGINE_SSL_write_direct(
                    ssl, this, sourceAddress, sourceLength, handshakeCallbacks);
        } finally {
            lock.readLock().unlock();
        }
    }
A utility wrapper that abstracts operations on the underlying native SSL instance.
common/src/main/java/org/conscrypt/NativeSsl.java