示例#1
0
        protected override IEnumerable <ParseStep> ParseSpecific(IRegexEngine engine, State initialState, StringBuilder matchedText)
        {
            // At this point, we know we'll match. Attempt to match everything else, until we hit max, a non-match, or the end of the string.

            // We need to save states as we go, in case we're asked to backtrack.
            var savedStates = new Stack <SavedState>();

            int matchedQuantity = Min;

            for (; Max == null || matchedQuantity < Max; matchedQuantity++)
            {
                // If the last state we saved was at the end of the string, there's no point in going any further...
                if (savedStates.Count > 0 && savedStates.Peek().State.Index >= engine.Input.Length)
                {
                    // Should we ever get here???
                    savedStates.Pop();
                    break;
                }

                if (engine.State.Index < engine.Input.Length)
                {
                    // We're not at the end of the string, so save state before attempting a match - since we're greedy, we leave breadcrumbs before doing anything.
                    savedStates.Push(new SavedState(engine.State, matchedText.ToString()));
                    yield return(ParseStep.StateSaved(this, engine.State, string.Format("Saving state - index {0}", engine.State.Index)));
                }
                else
                {
                    // It looks like we're at the end of the string - which means we're done. Time to report as such.
                    yield return(ParseStep.EndOfString(this, engine.State));

                    yield return(ParseStep.Pass(this, matchedText.ToString(), initialState, engine.State));

                    yield return(ParseStep.Break(this));

                    break;
                }

                var endOfMatch = false;

                // TODO: I think that we're going to need to use an enumerator here so we can initiate backtracking in our child and its descendants.
                foreach (var result in Child.Parse(engine))
                {
                    if (result.Type == ParseStepType.Break && ReferenceEquals(Child, result.Node))
                    {
                        break;
                    }

                    yield return(result);

                    if (ReferenceEquals(Child, result.Node))
                    {
                        if (result.Type == ParseStepType.Pass)
                        {
                            matchedText.Append(result.MatchedText);
                        }
                        else if (result.Type == ParseStepType.Fail)
                        {
                            endOfMatch = true;
                            foreach (var backtrackStep in Backtrack(engine, initialState, savedStates))
                            {
                                yield return(backtrackStep);
                            }
                            break;
                        }
                    }
                }

                if (endOfMatch)
                {
                    break;
                }
            }

            if (matchedQuantity >= Max)
            {
                // We've reached the maximum allowed quantity of repetitions, time to break;
                yield return(ParseStep.Pass(this, matchedText.ToString(), initialState, engine.State));

                yield return(ParseStep.Break(this));
            }

            // If we get here, it means that we're backtracking
            while (savedStates.Count > 0)
            {
                foreach (var backtrackStep in Backtrack(engine, initialState, savedStates))
                {
                    yield return(backtrackStep);
                }
            }

            // If we get here, we ran out of saved states to backtrack to - report failure.
            yield return(ParseStep.Fail(this, initialState, engine.State, "No backtrack is available"));

            if (engine.State.Index != initialState.Index)
            {
                yield return(ParseStep.ResetIndex(this, initialState, engine.State));

                engine.State = initialState;
            }

            yield return(ParseStep.Break(this));
        }
示例#2
0
        internal override IEnumerable <ParseStep> Parse(IRegexEngine engine)
        {
            yield return(ParseStep.BeginParse(this, engine.State));

            var initialState = engine.State;

            var choiceIndex = 0;

            foreach (var choice in Choices)
            {
                var matchedText  = "";
                var choicePassed = false;

                foreach (var result in choice.Parse(engine))
                {
                    if (ReferenceEquals(choice, result.Node) && result.Type == ParseStepType.Break)
                    {
                        break;
                    }

                    yield return(result);

                    if (ReferenceEquals(choice, result.Node))
                    {
                        if (result.Type == ParseStepType.Pass)
                        {
                            matchedText  = result.MatchedText;
                            choicePassed = true;

                            if (choiceIndex < Choices.Count - 1)
                            {
                                // Only save state if we're not the last choice...
                                yield return(ParseStep.StateSaved(this, initialState, string.Format("Saving state - index {0}", engine.State.Index)));
                            }
                        }
                    }
                }

                if (choicePassed)
                {
                    yield return(ParseStep.Pass(this, matchedText, initialState, engine.State));

                    yield return(ParseStep.Break(this)); // TODO: lazy quantifiers might act in a similar manner as alternation here...

                    yield return(ParseStep.Backtrack(this, initialState, engine.State));
                }
                else
                {
                    if (engine.State.Index != initialState.Index)
                    {
                        yield return(ParseStep.ResetIndex(this, initialState, engine.State));

                        engine.State = initialState;
                    }
                }

                choiceIndex++;
            }

            yield return(ParseStep.Fail(this, initialState, engine.State));

            yield return(ParseStep.Break(this));
        }