private static void TestRange(RegexContext context, SequenceBuffer <char> buffer)
{
var backtrackState = new BacktrackState(true, context.CurrentState);
int j = 0;
while (true)
{
if (buffer.IsPastEnd(context.Index))
{
backtrackState.AddZeroConsumed();
context.Push(backtrackState);
context.MoveToNextState();
break;
}
var(matches, consumed) = MatchStateHere(context.CurrentState, buffer, context.Index);
if (!matches || consumed == 0)
{
backtrackState.AddZeroConsumed();
context.Push(backtrackState);
context.MoveToNextState();
break;
}
backtrackState.AddConsumption(consumed);
context.AdvanceIndex(consumed);
j++;
if (j >= context.CurrentState.Maximum)
{
context.MoveToNextState();
break;
}
}
}
private static void TestZeroOrOne(RegexContext context, SequenceBuffer <char> buffer)
{
if (buffer.IsPastEnd(context.Index))
{
context.Push(new BacktrackState(false, context.CurrentState, 0));
context.MoveToNextState();
return;
}
var(matches, consumed) = MatchStateHere(context.CurrentState, buffer, context.Index);
context.Push(new BacktrackState(matches && consumed > 0, context.CurrentState, consumed));
context.AdvanceIndex(consumed);
context.MoveToNextState();
}
private static (bool matches, int length) MatchStateHere(State state, SequenceBuffer <char> context, int i)
{
if (context.IsPastEnd(i))
{
if (state.Type == StateType.EndOfInput)
{
return(true, 0);
}
return(false, 0);
}
if (state.Type == StateType.EndOfInput)
{
return(false, 0);
}
if (state.Type == StateType.MatchValue)
{
var match = state.ValuePredicate?.Invoke(context[i]) ?? false;
return(match, match ? 1 : 0);
}
if (state.Type == StateType.Group)
{
return(Test(state.Group !, context.CopyFrom(i)));
}
if (state.Type == StateType.Alternation)
{
foreach (var substate in state.Alternations !)
{
var(matches, consumed) = Test(substate, context.CopyFrom(i));
if (matches)
{
return(true, consumed);
}
}
return(false, 0);
}
throw new RegexException("Unsupported state type during match");
}