private static void AssignIdsToStates(FiniteAutomata automata)
{
var idProvider = new IDProvider();
var states = automata.GetStates();
foreach (var state in states)
{
state.Id = idProvider.GetNext();
}
}
// TODO: Think about:
// - Whether it's needed or not to remove all transitions from dfa2 accepting state (i.e. mCrossState[dfa1State][dfa2State.IsAccepting].RemoveAllransitions
// - What to do with trap states
internal void Construct(FiniteAutomata dfa1, FiniteAutomata dfa2)
{
var dfa1TrapState = AddTrapState(dfa1);
var dfa2TrapState = AddTrapState(dfa2);
var dfa1States = dfa1.GetStates();
var dfa2States = dfa2.GetStates();
BuildCrossStates(dfa1States, dfa2States);
StartState = mCrossStates[dfa1.StartState][dfa2.StartState];
//Terminator = new State("cross-terminator");
foreach (var dfa1SourceState in dfa1States)
{
foreach (var dfa2SourceState in dfa2States)
{
for (int i = 0; i <= Byte.MaxValue; i++)
{
var inputChar = InputChar.For((byte)i);
var dfa1DestinationState = dfa1SourceState.Transitions[inputChar][0];
var dfa2DestinationState = dfa2SourceState.Transitions[inputChar][0];
// Source state in cross-automata
var sourceState = mCrossStates[dfa1SourceState][dfa2SourceState];
sourceState.IsAccepting = dfa2SourceState.IsAccepting;
// This checks if we need to add this transition at all
if ((dfa2DestinationState == dfa2TrapState && dfa1DestinationState == dfa1TrapState) || dfa2SourceState.IsAccepting)
continue;
if (dfa1DestinationState.IsAccepting)
{
// In case we reach accepting state of the repeated automata, go to start
dfa1DestinationState = dfa1.StartState;
}
if (dfa2DestinationState == dfa2TrapState && dfa1DestinationState != dfa1TrapState)
{
// In case there is no transition in suffix automata, but there is one in repeated
// automata, go to start in suffix automata
dfa2DestinationState = dfa2.StartState;
}
var destinationState = mCrossStates[dfa1DestinationState][dfa2DestinationState];
sourceState.AddTransitionTo(destinationState, inputChar);
}
}
}
}
private State AddTrapState(FiniteAutomata dfa)
{
var trapState = new State("trap") {Id = int.MaxValue};
for (int i = 0; i <= Byte.MaxValue; i++)
{
trapState.AddTransitionTo(trapState, InputChar.For((byte) i));
}
var states = dfa.GetStates();
foreach (var state in states)
{
bool[] usedTransitions = new bool[Byte.MaxValue + 1]; // All nulls
foreach (var transition in state.Transitions)
{
usedTransitions[transition.Key.Value] = true; // mark used symbol
}
for (int i = 0; i <= Byte.MaxValue; i++)
{
if (!usedTransitions[i])
{
state.AddTransitionTo(trapState, InputChar.For((byte)i));
}
}
}
return trapState;
}
