Function nahpack::nahpack_encode_block

#[no_mangle]
pub extern "C" fn nahpack_encode_block(
    block: *const Header, 
    len: size_t, 
    context: *mut HpackContext, 
    callback: extern "C" fn(_: *mut c_void, _: *const uint8_t, _: size_t), 
    passthrough_ptr: *mut c_void
) -> ssize_t