//Adds a control character transition
private RegexTrie <T> addSpecialTransition(int controlCode, RegexTrie <T> endNodeOfPreviousComponent)
{
RegexTrie <T> startNodeOfCurrentComponent = new RegexTrie <T>();
//Connect start node to previous end node
endNodeOfPreviousComponent.AddEpsilonTransition(startNodeOfCurrentComponent);
//Use STX control character
return(startNodeOfCurrentComponent.GetOrAddChildNode((char)controlCode, 0));
}
//This adds the transitions required to make a group trie correspond to the correct quantified regex
private RegexTrie <T> joinQuantifiedTrie(MinMaxResult result,
RegexTrie <T> startNodeOfCurrentComponent,
RegexTrie <T> endNodeOfCurrentComponent,
RegexTrie <T> endNodeOfPreviousComponent)
{
//This is the end node which will be reached by epsilon transition in case of zeroed quantifiers
//or quantifiers with a number range of more than one, start node is used for zeroing
RegexTrie <T> epsilonEndNode = new RegexTrie <T>();
RegexTrie <T> epsilonStartNode = new RegexTrie <T>();
//This holds the end node used during the loop
RegexTrie <T> loopEndNode = endNodeOfCurrentComponent;
//Loop from 1 (one occurrence already exists) to max occurrences. If loop index is greater than min,
//add epsilon from iteration trie end to final trie end.
if (result.minOccurs > 1 || result.maxOccurs > 1)
{
//This is used as a model for copying, only needs to be calculated if there's a set number of occurrences
KeyValuePair <RegexTrie <T>, RegexTrie <T> > trieModel = copyTrie(startNodeOfCurrentComponent, endNodeOfCurrentComponent);
//Result of trie copy
KeyValuePair <RegexTrie <T>, RegexTrie <T> > trieCopy;
for (int index = 2; index <= result.maxOccurs; index++)
{
if (index <= result.maxOccurs)
{
//Copy the trie and link it to the end of trie
trieCopy = copyTrie(trieModel);
loopEndNode.AddEpsilonTransition(trieCopy.Key);
//If the index is equal or greater than minoccurs, add epsilon to end node
if (result.minOccurs <= index)
{
trieCopy.Value.AddEpsilonTransition(epsilonEndNode);
}
//Assign the end node of the copy as the end node of the component
loopEndNode = trieCopy.Value;
}
}
}
//If there's less than two occurrences, connect the end of the first span of the trie to the epsilon end trie
//Do this after the copy loop in order to not disturb the copying.
if (result.minOccurs < 2)
{
endNodeOfCurrentComponent.AddEpsilonTransition(epsilonEndNode);
}
//If the quantifier is starred, add epsilon from end to start
if (result.starred)
{
endNodeOfCurrentComponent.AddEpsilonTransition(startNodeOfCurrentComponent);
}
//If the quantifier is zeroed, add an epsilon from epsilon start node
//newCurrentTrie
if (result.zeroInclusive)
{
epsilonStartNode.AddEpsilonTransition(startNodeOfCurrentComponent);
epsilonStartNode.AddEpsilonTransition(epsilonEndNode);
startNodeOfCurrentComponent = epsilonStartNode;
}
//Connect trie to previous trie
endNodeOfPreviousComponent.AddEpsilonTransition(startNodeOfCurrentComponent);
return(epsilonEndNode);
}
//This checks for a quantifier immediately after the character, and joins the current trie to the end of the
//previous trie. Returns a pair of int (to increment string index) and the node to which further tries will be connected
private KeyValuePair <int, RegexTrie <T> > checkForQuantifier(
string sourceTail,
RegexTrie <T> endNodeOfCurrentComponent,
RegexTrie <T> startNodeOfCurrentComponent,
RegexTrie <T> endNodeOfPreviousComponent,
Stack <RegexTrie <T> > commonDestination)
{
char nextChar;
try
{
nextChar = sourceTail[0];
}
catch
{
//assign a non-special character to trigger the default case
nextChar = 'n';
}
switch (nextChar)
{
case '*':
{
return(new KeyValuePair <int, RegexTrie <T> >(1, joinQuantifiedTrie(
new MinMaxResult(1, 1, true, true),
startNodeOfCurrentComponent,
endNodeOfCurrentComponent,
endNodeOfPreviousComponent)));
}
case '+':
{
return(new KeyValuePair <int, RegexTrie <T> >(1, joinQuantifiedTrie(
new MinMaxResult(1, 1, true, false),
startNodeOfCurrentComponent,
endNodeOfCurrentComponent,
endNodeOfPreviousComponent)));
}
case '?':
{
return(new KeyValuePair <int, RegexTrie <T> >(1, joinQuantifiedTrie(
new MinMaxResult(1, 1, false, true),
startNodeOfCurrentComponent,
endNodeOfCurrentComponent,
endNodeOfPreviousComponent)));
}
case '{':
{
int closeBraceIndex = sourceTail.IndexOf('}');
string quantString = sourceTail.Substring(1, closeBraceIndex - 1);
MinMaxResult minMax = findMinMax(quantString);
return(new KeyValuePair <int, RegexTrie <T> >(closeBraceIndex + 1, joinQuantifiedTrie(
minMax,
startNodeOfCurrentComponent,
endNodeOfCurrentComponent,
endNodeOfPreviousComponent)));
}
default:
{
endNodeOfPreviousComponent.AddEpsilonTransition(startNodeOfCurrentComponent);
return(new KeyValuePair <int, RegexTrie <T> >(0, endNodeOfCurrentComponent));
}
}
}
//This has to keep track of four nodes: end of the previous component, start of the current component,
//end of the current component and the node that is connected to the end of the current component with
//an epsilon transition (which will become the end of the previous component for the next component).
public void AddToRegexTrie
(RegexTrie <T> trie,
string source,
T matchobject,
Stack <RegexTrie <T> > endStack,
Stack <RegexTrie <T> > startStack,
Stack <RegexTrie <T> > commonDestination)
{
RegexTrie <T> newTrie = new RegexTrie <T>();
//Current trie being added to
RegexTrie <T> endNodeOfCurrentComponent = trie;
//End of previous trie, to which the current trie is joined
RegexTrie <T> endNodeOfPreviousComponent = trie;
//End of previous trie, to which the current trie is joined
RegexTrie <T> startNodeOfCurrentComponent = trie;
//Push trie on the start stack
startStack.Push(trie);
//Push a null on the commonStart and commonDestination stacks
commonDestination.Push(null);
//Matching group counter.
byte groupCount = 1;
//True if previous character was an escape char
Boolean escapedCharacter = false;
//Variable for the character at the loop index
char currentChar;
//Holds the result of the quantifier check
KeyValuePair <int, RegexTrie <T> > quantifierCheckResult;
for (int stringIndex = 0; stringIndex < source.Length; stringIndex++)
{
currentChar = source[stringIndex];
//Check for escape character
if (currentChar == '\\')
{
escapedCharacter = true;
continue;
}
//If the character is escaped, just make it into a trie
if (escapedCharacter)
{
//Special char handling
if (currentChar == 't')
{
currentChar = '\t';
}
startNodeOfCurrentComponent = new RegexTrie <T>();
endNodeOfCurrentComponent = startNodeOfCurrentComponent.GetOrAddChildNode(currentChar, 0);
quantifierCheckResult = checkForQuantifier(
source.Substring(stringIndex + 1),
endNodeOfCurrentComponent,
startNodeOfCurrentComponent,
endNodeOfPreviousComponent,
commonDestination);
stringIndex += quantifierCheckResult.Key;
endNodeOfPreviousComponent = quantifierCheckResult.Value;
escapedCharacter = false;
continue;
}
//Else check character for special meaning
else
{
switch (currentChar)
{
//Open a new group
case '(':
{
//Push the previous trie to the end stack
endStack.Push(endNodeOfPreviousComponent);
//Create a new trie
endNodeOfPreviousComponent = new RegexTrie <T>();
//Push the newly created trie on the start stack
startStack.Push(endNodeOfPreviousComponent);
//Push a null trie on the common destination and start stacks (to be defined, if pipes are found)
commonDestination.Push(null);
break;
}
//Close a group
case ')':
{
//If common destination exists, add an epsilon transition to it
if (commonDestination.Peek() != null)
{
//Connect the end node and common destination as part of the same epsilon closure
commonDestination.Peek().AddEpsilonTransition(endNodeOfPreviousComponent);
endNodeOfPreviousComponent.AddEpsilonTransition(commonDestination.Peek());
//Move the current trie to common destination, as that's where the building will continue
//Pop the common destination, it won't be needed anymore
endNodeOfCurrentComponent = commonDestination.Pop();
}
else
{
endNodeOfCurrentComponent = endNodeOfPreviousComponent;
//Pop the null destination
commonDestination.Pop();
}
startNodeOfCurrentComponent = startStack.Pop();
endNodeOfPreviousComponent = endStack.Pop();
quantifierCheckResult = checkForQuantifier(
source.Substring(stringIndex + 1),
endNodeOfCurrentComponent,
startNodeOfCurrentComponent,
endNodeOfPreviousComponent,
commonDestination);
stringIndex += quantifierCheckResult.Key;
endNodeOfPreviousComponent = quantifierCheckResult.Value;
try
{
endStack.Peek();
}
//If we're at the top, add group number to each node of the trie
catch
{
addGroupNumbers(startNodeOfCurrentComponent, groupCount);
groupCount++;
}
break;
}
//Handle square bracket set
case '[':
{
startNodeOfCurrentComponent = new RegexTrie <T>();
endNodeOfCurrentComponent = new RegexTrie <T>();
//This skips over the closing square bracket, so there's no need for closing square bracket handling
stringIndex += handleSquareBracketGroup(startNodeOfCurrentComponent, endNodeOfCurrentComponent, source.Substring(stringIndex + 1));
quantifierCheckResult = checkForQuantifier(
source.Substring(stringIndex + 1),
endNodeOfCurrentComponent,
startNodeOfCurrentComponent,
endNodeOfPreviousComponent,
commonDestination);
stringIndex += quantifierCheckResult.Key;
endNodeOfPreviousComponent = quantifierCheckResult.Value;
break;
}
//Caret at the start: add a transition with a control character that won't exist in text.
//Feed the control character when finding matches.
case '^':
{
endNodeOfPreviousComponent = addSpecialTransition(2, endNodeOfPreviousComponent);
break;
}
//Dollar at end: add a transition with a control character that won't exist in text.
//Feed the control character when finding matches.
case '$':
{
endNodeOfPreviousComponent = addSpecialTransition(3, endNodeOfPreviousComponent);
break;
}
//Period handling
case '.':
{
startNodeOfCurrentComponent = new RegexTrie <T>();
endNodeOfCurrentComponent = new RegexTrie <T>();
//Add complement of null character
startNodeOfCurrentComponent.complementTransitions.Add(
new ComplementTransition <T>(
0,
endNodeOfCurrentComponent,
new List <char>(),
new List <KeyValuePair <char, char> >()
{
new KeyValuePair <char, char>((char)0, (char)0)
}));
quantifierCheckResult = checkForQuantifier(
source.Substring(stringIndex + 1),
endNodeOfCurrentComponent,
startNodeOfCurrentComponent,
endNodeOfPreviousComponent,
commonDestination);
stringIndex += quantifierCheckResult.Key;
endNodeOfPreviousComponent = quantifierCheckResult.Value;
break;
}
//Change previous end to common destination and move end node to common start
case '|':
{
if (commonDestination.Peek() == null)
{
commonDestination.Pop();
commonDestination.Push(endNodeOfPreviousComponent);
}
else
{
//Connect the end node and common destination as part of the same epsilon closure
commonDestination.Peek().AddEpsilonTransition(endNodeOfPreviousComponent);
endNodeOfPreviousComponent.AddEpsilonTransition(commonDestination.Peek());
}
endNodeOfPreviousComponent = startStack.Peek();
break;
}
default:
{
startNodeOfCurrentComponent = new RegexTrie <T>();
endNodeOfCurrentComponent = startNodeOfCurrentComponent.GetOrAddChildNode(currentChar, 0);
quantifierCheckResult = checkForQuantifier(
source.Substring(stringIndex + 1),
endNodeOfCurrentComponent,
startNodeOfCurrentComponent,
endNodeOfPreviousComponent,
commonDestination);
stringIndex += quantifierCheckResult.Key;
endNodeOfPreviousComponent = quantifierCheckResult.Value;
break;
}
}
}
}
//Link end node to common destination and start node to common start if they exist
if (commonDestination.Peek() != null)
{
endNodeOfPreviousComponent.AddEpsilonTransition(commonDestination.Peek());
endNodeOfPreviousComponent = commonDestination.Pop();
}
//Add translation and replace fields to the current trie
endNodeOfPreviousComponent.matches = new List <T> {
matchobject
};
}
