module BinData::BasePrimitive::AssertedValuePlugin

def _value
  reading? ? @value : eval_parameter(:asserted_value)
end

def assert!
  assert_value(snapshot)
end

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

def assign(val)
  assert_value(val)
  super(val)
end

def do_read(io) #:nodoc:
  super(io)
  assert!
end