Improved submatch tracking by storing all group indices as a part of the state, which is viewed as a 'thread'

matching.go

@@ -62,15 +62,21 @@ func (g Group) isValid() bool {
 // the second ret val is true.
 // The third ret val is a list of all the group numbers of all the opening parentheses we crossed,
 // and the fourth is a list of all the closing parentheses we passed
-func takeZeroState(states []*State) (rtv []*State, isZero bool, openParenGroups []int, closeParenGroups []int) {
+func takeZeroState(states []*State, numGroups int, idx int) (rtv []*State, isZero bool) {
 	for _, state := range states {
 		if len(state.transitions[EPSILON]) > 0 {
 			for _, s := range state.transitions[EPSILON] {
+				if s.threadGroups == nil {
+					s.threadGroups = newMatch(numGroups + 1)
+				}
+				copy(s.threadGroups, state.threadGroups)
 				if s.groupBegin {
-					openParenGroups = append(openParenGroups, s.groupNum)
+					s.threadGroups[s.groupNum].startIdx = idx
+					//					openParenGroups = append(openParenGroups, s.groupNum)
 				}
 				if s.groupEnd {
-					closeParenGroups = append(closeParenGroups, s.groupNum)
+					s.threadGroups[s.groupNum].endIdx = idx
+					//					closeParenGroups = append(closeParenGroups, s.groupNum)
 				}
 			}
 			rtv = append(rtv, state.transitions[EPSILON]...)
@@ -78,10 +84,10 @@ func takeZeroState(states []*State) (rtv []*State, isZero bool, openParenGroups
 	}
 	for _, state := range rtv {
 		if len(state.transitions[EPSILON]) > 0 {
-			return rtv, true, openParenGroups, closeParenGroups
+			return rtv, true
 		}
 	}
-	return rtv, false, openParenGroups, closeParenGroups
+	return rtv, false
 }
 
 // zeroMatchPossible returns true if a zero-length match is possible
@@ -90,20 +96,16 @@ func takeZeroState(states []*State) (rtv []*State, isZero bool, openParenGroups
 // so I should probably put it in a function.
 // It also returns all the capturing groups that both begin and end at the current index.
 // This is because, by definition, zero-states don't move forward in the string.
-func zeroMatchPossible(str []rune, idx int, states ...*State) (bool, []int, []int) {
+func zeroMatchPossible(str []rune, idx int, numGroups int, states ...*State) (bool, []int, []int) {
 	allOpenParenGroups := make([]int, 0)
 	allCloseParenGroups := make([]int, 0)
-	zeroStates, isZero, openParenGroups, closeParenGroups := takeZeroState(states)
+	zeroStates, isZero := takeZeroState(states, numGroups, idx)
-	allOpenParenGroups = append(allOpenParenGroups, openParenGroups...)
-	allCloseParenGroups = append(allCloseParenGroups, closeParenGroups...)
 	tempstates := make([]*State, 0, len(zeroStates)+len(states))
 	tempstates = append(tempstates, states...)
 	tempstates = append(tempstates, zeroStates...)
 	num_appended := 0 // number of unique states addded to tempstates
 	for isZero == true {
-		zeroStates, isZero, openParenGroups, closeParenGroups = takeZeroState(tempstates)
+		zeroStates, isZero = takeZeroState(tempstates, numGroups, idx)
-		allOpenParenGroups = append(allOpenParenGroups, openParenGroups...)
-		allCloseParenGroups = append(allCloseParenGroups, closeParenGroups...)
 		tempstates, num_appended = unique_append(tempstates, zeroStates...)
 		if num_appended == 0 { // break if we haven't appended any more unique values
 			break
@@ -180,7 +182,7 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 			if start.groupBegin {
 				to_return[start.groupNum].startIdx = offset
 			}
-			if ok, openGrps, closeGrps := zeroMatchPossible(str, offset, start); ok {
+			if ok, openGrps, closeGrps := zeroMatchPossible(str, offset, numGroups, start); ok {
 				for _, gIdx := range openGrps {
 					to_return[gIdx].startIdx = offset
 				}
@@ -227,9 +229,11 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 		i++ // Advance to next character (if we aren't at a 0-state, which doesn't match anything), so that we can check for transitions. If we advance at a 0-state, we will never get a chance to match the first character
 	}
 
+	start.threadGroups = newMatch(numGroups + 1)
 	// Check if the start state begins a group - if so, add the start index to our list
 	if start.groupBegin {
-		tempIndices[start.groupNum].startIdx = i
+		start.threadGroups[start.groupNum].startIdx = i
+		//		tempIndices[start.groupNum].startIdx = i
 	}
 
 	currentStates = append(currentStates, start)
@@ -241,23 +245,11 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 		zeroStates := make([]*State, 0)
 		// Keep taking zero-states, until there are no more left to take
 		// Objective: If any of our current states have transitions to 0-states, replace them with the 0-state. Do this until there are no more transitions to 0-states, or there are no more unique 0-states to take.
-		zeroStates, isZero, openParenGroups, closeParenGroups := takeZeroState(currentStates)
+		zeroStates, isZero := takeZeroState(currentStates, numGroups, i)
-		for _, val := range openParenGroups {
-			tempIndices[val].startIdx = i
-		}
-		for _, val := range closeParenGroups {
-			tempIndices[val].endIdx = i
-		}
 		tempStates = append(tempStates, zeroStates...)
 		num_appended := 0
 		for isZero == true {
-			zeroStates, isZero, openParenGroups, closeParenGroups = takeZeroState(tempStates)
+			zeroStates, isZero = takeZeroState(tempStates, numGroups, i)
-			for _, val := range openParenGroups {
-				tempIndices[val].startIdx = i
-			}
-			for _, val := range closeParenGroups {
-				tempIndices[val].endIdx = i
-			}
 			tempStates, num_appended = unique_append(tempStates, zeroStates...)
 			if num_appended == 0 { // Break if we haven't appended any more unique values
 				break
@@ -271,6 +263,7 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 		numStatesMatched := 0         // The number of states which had at least 1 match for this round
 		assertionFailed := false      // Whether or not an assertion failed for this round
 		lastStateInList := false      // Whether or not a last state was in our list of states
+		var lastStatePtr *State = nil // Pointer to the last-state, if it was found
 		lastLookaroundInList := false // Whether or not a last state (that is a lookaround) was in our list of states
 		for _, state := range currentStates {
 			matches, numMatches := state.matchesFor(str, i)
@@ -278,6 +271,12 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 				numStatesMatched++
 				tempStates = append(tempStates, matches...)
 				foundPath = true
+				for _, m := range matches {
+					if m.threadGroups == nil {
+						m.threadGroups = newMatch(numGroups + 1)
+					}
+					copy(m.threadGroups, state.threadGroups)
+				}
 			}
 			if numMatches < 0 {
 				assertionFailed = true
@@ -287,6 +286,7 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 					lastLookaroundInList = true
 				}
 				lastStateInList = true
+				lastStatePtr = state
 			}
 		}
 
@@ -309,14 +309,27 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 				return false, []Group{}, i
 			}
 		}
+		// Check if we can find a state in our list that is:
+		// 	a. A last-state
+		// 	b. Empty
+		// 	c. Doesn't assert anything
+		for _, s := range currentStates {
+			if s.isLast && s.isEmpty && s.assert == NONE {
+				lastStatePtr = s
+				lastStateInList = true
+			}
+		}
 		if lastStateInList { // A last-state was in the list of states. add the matchIndex to our MatchIndex list
+			for j := 1; j < numGroups+1; j++ {
+				tempIndices[j] = lastStatePtr.threadGroups[j]
+			}
 			endIdx = i
 			tempIndices[0] = Group{startIdx, endIdx}
 		}
 
 		// Check if we can find a zero-length match
 		if foundPath == false {
-			if ok, _, _ := zeroMatchPossible(str, i, currentStates...); ok {
+			if ok, _, _ := zeroMatchPossible(str, i, numGroups, currentStates...); ok {
 				if tempIndices[0].isValid() == false {
 					tempIndices[0] = Group{startIdx, startIdx}
 				}
@@ -345,23 +358,11 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 
 	// End-of-string reached. Go to any 0-states, until there are no more 0-states to go to. Then check if any of our states are in the end position.
 	// This is the exact same algorithm used inside the loop, so I should probably put it in a function.
-	zeroStates, isZero, openParenGroups, closeParenGroups := takeZeroState(currentStates)
+	zeroStates, isZero := takeZeroState(currentStates, numGroups, i)
-	for _, val := range openParenGroups {
-		tempIndices[val].startIdx = i
-	}
-	for _, val := range closeParenGroups {
-		tempIndices[val].endIdx = i
-	}
 	tempStates = append(tempStates, zeroStates...)
 	num_appended := 0 // Number of unique states addded to tempStates
 	for isZero == true {
-		zeroStates, isZero, openParenGroups, closeParenGroups = takeZeroState(tempStates)
+		zeroStates, isZero = takeZeroState(tempStates, numGroups, i)
-		for _, val := range openParenGroups {
-			tempIndices[val].startIdx = i
-		}
-		for _, val := range closeParenGroups {
-			tempIndices[val].endIdx = i
-		}
 		tempStates, num_appended = unique_append(tempStates, zeroStates...)
 		if num_appended == 0 { // Break if we haven't appended any more unique values
 			break
@@ -376,6 +377,9 @@ func findAllMatchesHelper(start *State, str []rune, offset int, numGroups int) (
 		// make sure the assertion checks out.
 		if state.isLast && startIdx < len(str) {
 			if state.assert == NONE || state.checkAssertion(str, i) {
+				for j := 1; j < numGroups+1; j++ {
+					tempIndices[j] = state.threadGroups[j]
+				}
 				endIdx = i
 				tempIndices[0] = Group{startIdx, endIdx}
 			}

nfa.go

@@ -33,10 +33,11 @@ type State struct {
 	except                     []rune           // Only valid if allChars is true - match all characters _except_ the ones in this block. Useful for inverting character classes.
 	lookaroundRegex            string           // Only for lookaround states - Contents of the regex that the lookaround state holds
 	lookaroundNFA              *State           // Holds the NFA of the lookaroundRegex - if it exists
-	lookaroundNumCaptureGroups int              // Number of capturing groups if current node is a lookaround
+	lookaroundNumCaptureGroups int              // Number of capturing groups in lookaround regex if current node is a lookaround
 	groupBegin                 bool             // Whether or not the node starts a capturing group
 	groupEnd                   bool             // Whether or not the node ends a capturing group
 	groupNum                   int              // Which capturing group the node starts / ends
+	threadGroups               []Group          // Assuming that a state is part of a 'thread' in the matching process, this array stores the indices of capturing groups in the current thread. As matches are found for this state, its groups will be copied over.
 }
 
 // Clones the NFA starting from the given state.