class Argon2::Engine

def self.hash_argon2i(password, salt, t_cost, m_cost, out_len = nil)
  out_len = (out_len || Constants::OUT_LEN).to_i
  raise ArgonHashFail, "Invalid output length" if out_len < 1
  result = ''
  FFI::MemoryPointer.new(:char, out_len) do |buffer|
    ret = Ext.argon2i_hash_raw(t_cost, 1 << m_cost, 1, password,
                               password.length, salt, salt.length,
                               buffer, out_len)
    raise ArgonHashFail, ERRORS[ret.abs] unless ret.zero?
    result = buffer.read_string(out_len)
  end
  result.unpack('H*').join
end