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Added support for non-capturing groups

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This commit is contained in:
Aadhavan Srinivasan
2024-12-18 15:22:43 -05:00
parent 8d6e1a41a5
commit 98f4c9e418
2 changed files with 27 additions and 11 deletions
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35
main.go
View File

@@ -51,6 +51,9 @@ func shuntingYard(re string) []postfixNode {
// Eventually, I might be able to add it into the main parsing loop, to reduce the time
// complexity.
// A numeric range has the syntax: <num1-num2>. Ir matches all numbers in this range.
//
// Also check for non-capturing groups. The LPAREN of a non-capturing group looks like this: '(?:'
// I take this out, and put in a special character - NONCAPLPAREN_CHAR.
for i := 0; i < len(re_runes_orig); i++ {
c := re_runes_orig[i]
if c == '<' && (i == 0 || (re_runes_orig[i-1] != '\\' && re_runes_orig[i-1] != '?')) {
@@ -82,7 +85,9 @@ func shuntingYard(re string) []postfixNode {
fmt.Sscanf(tmpStr, "%d-%d", &rangeStart, &rangeEnd)
regex := range2regex(rangeStart, rangeEnd)
re_runes = append(re_runes, []rune(regex)...)
} else if c == '(' && i < len(re_runes_orig)-2 && re_runes_orig[i+1] == '?' && re_runes_orig[i+2] == ':' {
re_runes = append(re_runes, NONCAPLPAREN_CHAR)
i += 2
} else {
re_runes = append(re_runes, c)
}
@@ -148,7 +153,11 @@ func shuntingYard(re string) []postfixNode {
}
re_postfix = append(re_postfix, re_runes[i]) // Append closing brace
}
if i < len(re_runes) && re_runes[i] == '(' && (i == 0 || re_runes[i-1] != '\\') && (i < len(re_runes)-1 && re_runes[i+1] == '?') { // Unescaped open parentheses followed by question mark = lokaround. Don't mess with it.
if i < len(re_runes)-3 && string(re_runes[i+1:i+4]) == "(?:" { // Non-capturing lparen
re_postfix = append(re_postfix, NONCAPLPAREN_CHAR)
i += 3
}
if i < len(re_runes) && re_runes[i] == '(' && (i == 0 || re_runes[i-1] != '\\') && (i < len(re_runes)-2 && re_runes[i+1] == '?' && slices.Contains([]rune{'=', '!', '<'}, re_runes[i+2])) { // Unescaped open parentheses followed by question mark then '<', '!' or '=' => lokaround. Don't mess with it.
i++ // Step inside
if i == len(re_runes)-1 || (re_runes[i+1] != '=' && re_runes[i+1] != '!' && re_runes[i+1] != '<') {
panic("Invalid regex. Lookaround intended?")
@@ -174,7 +183,7 @@ func shuntingYard(re string) []postfixNode {
}
continue
}
if i < len(re_runes) && (re_runes[i] != '(' && re_runes[i] != '|' && re_runes[i] != '\\') || (i > 0 && re_runes[i-1] == '\\') { // Every character should be concatenated if it is escaped
if i < len(re_runes) && (re_runes[i] != '(' && re_runes[i] != NONCAPLPAREN_CHAR && re_runes[i] != '|' && re_runes[i] != '\\') || (i > 0 && re_runes[i-1] == '\\') { // Every character should be concatenated if it is escaped
if i < len(re_runes)-1 {
if re_runes[i+1] != '|' && re_runes[i+1] != '*' && re_runes[i+1] != '+' && re_runes[i+1] != '?' && re_runes[i+1] != ')' && re_runes[i+1] != '{' {
re_postfix = append(re_postfix, CONCAT)
@@ -197,7 +206,7 @@ func shuntingYard(re string) []postfixNode {
b. If not, keep popping from opStack (and appending to outQueue) until:
i. opStack is empty, OR
ii. current character has greater priority than top of opStack
3. If current character is '(', push to opStack
3. If current character is '(' or NONCAPLPAREN_CHAR, push to opStack
4. If current character is ')', pop from opStack (and append to outQueue) until '(' is found. Discard parantheses.
5. If current character is '[', find all the characters until ']', then create a postfixNode containing all these contents. Add this node to outQueue.
6. If current character is '{', find the appropriate numeric specifier (range start, range end). Apply the range to the postfixNode at the end of outQueue.
@@ -389,22 +398,28 @@ func shuntingYard(re string) []postfixNode {
outQueue[idx].startReps = startRangeNum
outQueue[idx].endReps = endRangeNum
}
if c == '(' {
if c == '(' || c == NONCAPLPAREN_CHAR {
opStack = append(opStack, c)
outQueue = append(outQueue, newPostfixNode(c))
if c == '(' { // We only push _capturing_ group parentheses to outQueue
outQueue = append(outQueue, newPostfixNode(c))
}
numOpenParens++
}
if c == ')' {
// Keep popping from opStack until we encounter an opening parantheses. Panic if we reach the end of the stack.
for val, err := peek(opStack); val != '('; val, err = peek(opStack) {
// Keep popping from opStack until we encounter an opening parantheses or a NONCAPLPAREN_CHAR. Panic if we reach the end of the stack.
var val rune
var err error
for val, err = peek(opStack); val != '(' && val != NONCAPLPAREN_CHAR; val, err = peek(opStack) {
if err != nil {
panic("ERROR: Imbalanced parantheses.")
}
to_append := mustPop(&opStack)
outQueue = append(outQueue, newPostfixNode(to_append))
}
_ = mustPop(&opStack) // Get rid of opening parentheses
outQueue = append(outQueue, newPostfixNode(')')) // Add closing parentheses
_ = mustPop(&opStack) // Get rid of opening parentheses
if val == '(' { // Whatever was inside the parentheses was a _capturing_ group, so we append the closing parentheses as well
outQueue = append(outQueue, newPostfixNode(')')) // Add closing parentheses
}
numOpenParens--
}
}

3
misc.go
View File

@@ -13,6 +13,7 @@ var RBRACKET rune = 0xF0001
var ANY_CHAR rune = 0xF0002 // Represents any character - used for states where the allChars flag is on.
var LPAREN_CHAR rune = 0xF0003 // Parentheses in regex are concatenated with this - it acts as a pseudio-parentheses
var RPAREN_CHAR rune = 0xF0004
var NONCAPLPAREN_CHAR rune = 0xF0005 // Represents a non-capturing group's LPAREN
// Returns true if str[idx] and str[idx-1] are separated by a word boundary.
func isWordBoundary(str []rune, idx int) bool {
@@ -26,7 +27,7 @@ func isWordBoundary(str []rune, idx int) bool {
func isNormalChar(c rune) bool {
specialChars := []rune(`?*\^${}()+|[].~<>`)
specialChars = append(specialChars, LBRACKET, RBRACKET)
specialChars = append(specialChars, LBRACKET, RBRACKET, NONCAPLPAREN_CHAR)
return !slices.Contains(specialChars, c)
}