public BacktrackPoint(BacktrackPoint previous,
StackFrame callStack,
Result<char, int> partialResult)
{
Previous = previous;
CallStack = callStack;
PartialResult = partialResult;
}
protected override Result<char, Match2> Parse(ArrayConsList<char> consList, int afterLastMatchIndex)
{
BacktrackPoint lastBacktrackPoint = null;
StackFrame callStack = new GroupStackFrame(null, Pattern);
var partialResult = new Result<char, int>(0, consList);
while (callStack != null)
{
if (callStack is QuantifierStackFrame)
{
QuantifierStackFrame quantStackFrame = (QuantifierStackFrame)callStack;
if (quantStackFrame.IsPositionChanged(partialResult.Tree))
{
lastBacktrackPoint = new BacktrackPoint(lastBacktrackPoint,
quantStackFrame.SecondAlternative(partialResult.Tree),
partialResult);
callStack = quantStackFrame.FirstAlternative(partialResult.Tree);
}
else
callStack = quantStackFrame.Parent;
}
else
{
BasePattern currentPattern = callStack.RemainingChildren.Head;
if (currentPattern.MinCharLength > partialResult.Rest.Length)
partialResult = null;
else
{
callStack = ((GroupStackFrame)callStack).MoveToNextChild();
switch (currentPattern.Type)
{
case PatternType.Group:
callStack = new GroupStackFrame(callStack, ((GroupPattern)currentPattern).Patterns);
break;
case PatternType.Quantifier:
var quant = (QuantifierPattern)currentPattern;
quant.AssertCanonicalForm();
if (quant.MinOccurrences == quant.MaxOccurrences)
callStack = new GroupStackFrame(callStack,
new RepeaterConsList<BasePattern>(quant.ChildPattern,
quant.MinOccurrences));
else
callStack = new QuantifierStackFrame(callStack, quant);
break;
case PatternType.Alternation:
var alternatives = ((AlternationPattern)currentPattern).Alternatives;
foreach (var alt in alternatives.Skip(1).Reverse())
lastBacktrackPoint = new BacktrackPoint(lastBacktrackPoint,
new GroupStackFrame(callStack, alt),
partialResult);
callStack = new GroupStackFrame(callStack, alternatives.First());
break;
case PatternType.Anchor:
if (!doesAnchorMatch(((AnchorPattern)currentPattern).AnchorType,
(ArrayConsList<char>)partialResult.Rest,
afterLastMatchIndex))
partialResult = null;
break;
case PatternType.Char:
partialResult = parseChar(partialResult, ((CharPattern)currentPattern).IsMatch);
break;
default:
throw new ApplicationException(
string.Format("BacktrackingMatcher: unrecognized pattern type ({0}).",
currentPattern.GetType().Name));
}
}
if (partialResult == null)
{
if (lastBacktrackPoint != null)
{
callStack = lastBacktrackPoint.CallStack;
partialResult = lastBacktrackPoint.PartialResult;
lastBacktrackPoint = lastBacktrackPoint.Previous;
}
else
return new Result<char, Match2>(Match2.Empty, consList);
}
}
callStack = unwindEmptyFrames(callStack);
}
return new Result<char, Match2>(
new Match2(consList.ArrayIndex,
partialResult.Tree,
consList.AsEnumerable().Take(partialResult.Tree).AsString()),
partialResult.Rest);
}