public void AycockHorspoolAlgorithmShouldAcceptVulnerableGrammar()
{
var a = new TerminalLexerRule(
new CharacterTerminal('a'),
new TokenType("a"));
ProductionExpression
SPrime = "S'",
S = "S",
A = "A",
E = "E";
SPrime.Rule = S;
S.Rule = (Expr)S | A + A + A + A;
A.Rule = (Expr)"a" | E;
var expression = new GrammarExpression(
SPrime,
new[] { SPrime, S, A, E });
var grammar = expression.ToGrammar();
var parseEngine = new ParseEngine(grammar);
parseEngine.Pulse(new Token("a", 0, a.TokenType));
var privateObject = new PrivateObject(parseEngine);
var chart = privateObject.GetField("_chart") as Chart;
Assert.IsNotNull(chart);
Assert.AreEqual(2, chart.Count);
Assert.IsTrue(parseEngine.IsAccepted());
}
private bool TryParseExistingToken()
{
var anyLexemes = this.tokenLexemes.Count > 0;
if (!anyLexemes)
{
return(false);
}
var i = 0;
var size = this.tokenLexemes.Count;
while (i < size)
{
var lexeme = this.tokenLexemes[i];
if (lexeme.IsAccepted())
{
i++;
}
else
{
if (i < size - 1)
{
this.tokenLexemes[i] = this.tokenLexemes[size - 1];
this.tokenLexemes[size - 1] = lexeme;
}
size--;
}
}
var anyMatches = size > 0;
if (!anyMatches)
{
return(false);
}
i = this.tokenLexemes.Count - 1;
while (i >= size)
{
this.tokenLexemes.RemoveAt(i);
i--;
}
if (!ParseEngine.Pulse(this.tokenLexemes))
{
return(false);
}
for (i = 0; i < this.triviaAccumulator.Count; i++)
{
foreach (var tokenLexeme in this.tokenLexemes)
{
tokenLexeme.AddLeadingTrivia(this.triviaAccumulator[i]);
}
}
this.triviaAccumulator.Clear();
this.previousTokenLexemes.Clear();
this.previousTokenLexemes.AddRange(this.tokenLexemes);
this.tokenLexemes.Clear();
return(true);
}
