Function emit 

pub unsafe extern "C" fn emit(
    write_ptr: u32,
    write_len: u32,
    read_ptr: u32,
    read_len: u32,
) -> i64

Emit a transaction from this hook. @param read_ptr Memory location of a buffer containing the fully formed binary transaction to emit. @param read_len The length of the transaction. @return A negative integer if the emission failed.