module BinData::BasePrimitive::AssertedValuePlugin

def assert_value(current_value)
  expected = eval_parameter(:asserted_value, :value => current_value)
  if not expected
    raise ValidityError,
          "value '#{current_value}' not as expected for #{debug_name}"
  elsif current_value != expected and expected != true
    raise ValidityError,
          "value is '#{current_value}' but " +
          "expected '#{expected}' for #{debug_name}"
  end
end