mirror of
https://github.com/VictoriaMetrics/VictoriaMetrics.git
synced 2024-12-18 22:52:11 +01:00
352 lines
8.6 KiB
Go
352 lines
8.6 KiB
Go
package regexutil
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import (
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"fmt"
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"regexp/syntax"
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"sort"
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"strings"
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)
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// RemoveStartEndAnchors removes '^' at the start of expr and '$' at the end of the expr.
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func RemoveStartEndAnchors(expr string) string {
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for strings.HasPrefix(expr, "^") {
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expr = expr[1:]
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}
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for strings.HasSuffix(expr, "$") && !strings.HasSuffix(expr, "\\$") {
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expr = expr[:len(expr)-1]
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}
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return expr
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}
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// GetOrValuesRegex returns "or" values from the given regexp expr.
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//
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// It returns ["foo", "bar"] for "foo|bar" regexp.
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// It returns ["foo"] for "foo" regexp.
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// It returns [""] for "" regexp.
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// It returns an empty list if it is impossible to extract "or" values from the regexp.
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func GetOrValuesRegex(expr string) []string {
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return getOrValuesRegex(expr, true)
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}
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// GetOrValuesPromRegex returns "or" values from the given Prometheus-like regexp expr.
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//
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// It ignores start and end anchors ('^') and ('$') at the start and the end of expr.
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// It returns ["foo", "bar"] for "foo|bar" regexp.
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// It returns ["foo"] for "foo" regexp.
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// It returns [""] for "" regexp.
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// It returns an empty list if it is impossible to extract "or" values from the regexp.
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func GetOrValuesPromRegex(expr string) []string {
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expr = RemoveStartEndAnchors(expr)
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return getOrValuesRegex(expr, false)
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}
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func getOrValuesRegex(expr string, keepAnchors bool) []string {
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prefix, tailExpr := simplifyRegex(expr, keepAnchors)
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if tailExpr == "" {
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return []string{prefix}
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}
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sre, err := parseRegexp(tailExpr)
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if err != nil {
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return nil
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}
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orValues := getOrValues(sre)
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// Sort orValues for faster index seek later
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sort.Strings(orValues)
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if len(prefix) > 0 {
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// Add prefix to orValues
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for i, orValue := range orValues {
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orValues[i] = prefix + orValue
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}
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}
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return orValues
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}
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func getOrValues(sre *syntax.Regexp) []string {
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switch sre.Op {
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case syntax.OpCapture:
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return getOrValues(sre.Sub[0])
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case syntax.OpLiteral:
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v, ok := getLiteral(sre)
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if !ok {
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return nil
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}
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return []string{v}
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case syntax.OpEmptyMatch:
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return []string{""}
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case syntax.OpAlternate:
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a := make([]string, 0, len(sre.Sub))
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for _, reSub := range sre.Sub {
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ca := getOrValues(reSub)
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if len(ca) == 0 {
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return nil
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}
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a = append(a, ca...)
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if len(a) > maxOrValues {
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// It is cheaper to use regexp here.
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return nil
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}
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}
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return a
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case syntax.OpCharClass:
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a := make([]string, 0, len(sre.Rune)/2)
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for i := 0; i < len(sre.Rune); i += 2 {
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start := sre.Rune[i]
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end := sre.Rune[i+1]
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for start <= end {
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a = append(a, string(start))
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start++
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if len(a) > maxOrValues {
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// It is cheaper to use regexp here.
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return nil
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}
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}
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}
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return a
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case syntax.OpConcat:
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if len(sre.Sub) < 1 {
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return []string{""}
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}
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prefixes := getOrValues(sre.Sub[0])
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if len(prefixes) == 0 {
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return nil
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}
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if len(sre.Sub) == 1 {
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return prefixes
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}
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sre.Sub = sre.Sub[1:]
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suffixes := getOrValues(sre)
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if len(suffixes) == 0 {
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return nil
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}
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if len(prefixes)*len(suffixes) > maxOrValues {
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// It is cheaper to use regexp here.
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return nil
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}
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a := make([]string, 0, len(prefixes)*len(suffixes))
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for _, prefix := range prefixes {
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for _, suffix := range suffixes {
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s := prefix + suffix
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a = append(a, s)
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}
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}
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return a
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default:
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return nil
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}
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}
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func getLiteral(sre *syntax.Regexp) (string, bool) {
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if sre.Op == syntax.OpCapture {
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return getLiteral(sre.Sub[0])
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}
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if sre.Op == syntax.OpLiteral && sre.Flags&syntax.FoldCase == 0 {
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return string(sre.Rune), true
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}
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return "", false
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}
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const maxOrValues = 100
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// SimplifyRegex simplifies the given regexp expr.
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//
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// It returns plaintext pefix and the remaining regular expression
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// without capturing parens.
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func SimplifyRegex(expr string) (string, string) {
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prefix, suffix := simplifyRegex(expr, true)
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sre := mustParseRegexp(suffix)
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if isDotOp(sre, syntax.OpStar) {
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return prefix, ""
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}
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if sre.Op == syntax.OpConcat {
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subs := sre.Sub
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if prefix == "" {
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// Drop .* at the start
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for len(subs) > 0 && isDotOp(subs[0], syntax.OpStar) {
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subs = subs[1:]
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}
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}
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// Drop .* at the end.
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for len(subs) > 0 && isDotOp(subs[len(subs)-1], syntax.OpStar) {
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subs = subs[:len(subs)-1]
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}
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sre.Sub = subs
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if len(subs) == 0 {
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return prefix, ""
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}
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suffix = sre.String()
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}
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return prefix, suffix
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}
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// SimplifyPromRegex simplifies the given Prometheus-like expr.
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//
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// It returns plaintext prefix and the remaining regular expression
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// with dropped '^' and '$' anchors at the beginning and at the end
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// of the regular expression.
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//
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// The function removes capturing parens from the expr,
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// so it cannot be used when capturing parens are necessary.
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func SimplifyPromRegex(expr string) (string, string) {
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return simplifyRegex(expr, false)
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}
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func simplifyRegex(expr string, keepAnchors bool) (string, string) {
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sre, err := parseRegexp(expr)
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if err != nil {
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// Cannot parse the regexp. Return it all as prefix.
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return expr, ""
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}
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sre = simplifyRegexp(sre, keepAnchors, keepAnchors)
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if sre == emptyRegexp {
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return "", ""
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}
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v, ok := getLiteral(sre)
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if ok {
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return v, ""
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}
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var prefix string
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if sre.Op == syntax.OpConcat {
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prefix, ok = getLiteral(sre.Sub[0])
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if ok {
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sre.Sub = sre.Sub[1:]
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if len(sre.Sub) == 0 {
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return prefix, ""
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}
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sre = simplifyRegexp(sre, true, keepAnchors)
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}
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}
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if _, err := syntax.Compile(sre); err != nil {
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// Cannot compile the regexp. Return it all as prefix.
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return expr, ""
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}
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s := sre.String()
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s = strings.ReplaceAll(s, "(?:)", "")
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s = strings.ReplaceAll(s, "(?s:.)", ".")
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s = strings.ReplaceAll(s, "(?m:$)", "$")
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return prefix, s
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}
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func simplifyRegexp(sre *syntax.Regexp, keepBeginOp, keepEndOp bool) *syntax.Regexp {
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s := sre.String()
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for {
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sre = simplifyRegexpExt(sre, keepBeginOp, keepEndOp)
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sre = sre.Simplify()
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if !keepBeginOp && sre.Op == syntax.OpBeginText {
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sre = emptyRegexp
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} else if !keepEndOp && sre.Op == syntax.OpEndText {
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sre = emptyRegexp
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}
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sNew := sre.String()
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if sNew == s {
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return sre
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}
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sre = mustParseRegexp(sNew)
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s = sNew
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}
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}
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func simplifyRegexpExt(sre *syntax.Regexp, keepBeginOp, keepEndOp bool) *syntax.Regexp {
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switch sre.Op {
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case syntax.OpCapture:
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// Substitute all the capture regexps with non-capture regexps.
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sre.Op = syntax.OpAlternate
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sre.Sub[0] = simplifyRegexpExt(sre.Sub[0], keepBeginOp, keepEndOp)
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if sre.Sub[0] == emptyRegexp {
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return emptyRegexp
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}
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return sre
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case syntax.OpStar, syntax.OpPlus, syntax.OpQuest, syntax.OpRepeat:
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sre.Sub[0] = simplifyRegexpExt(sre.Sub[0], keepBeginOp, keepEndOp)
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if sre.Sub[0] == emptyRegexp {
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return emptyRegexp
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}
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return sre
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case syntax.OpAlternate:
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// Do not remove empty captures from OpAlternate, since this may break regexp.
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for i, sub := range sre.Sub {
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sre.Sub[i] = simplifyRegexpExt(sub, keepBeginOp, keepEndOp)
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}
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return sre
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case syntax.OpConcat:
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subs := sre.Sub[:0]
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for i, sub := range sre.Sub {
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sub = simplifyRegexpExt(sub, keepBeginOp || len(subs) > 0, keepEndOp || i+1 < len(sre.Sub))
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if sub != emptyRegexp {
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subs = append(subs, sub)
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}
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}
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sre.Sub = subs
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// Remove anchros from the beginning and the end of regexp, since they
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// will be added later.
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if !keepBeginOp {
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for len(sre.Sub) > 0 && sre.Sub[0].Op == syntax.OpBeginText {
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sre.Sub = sre.Sub[1:]
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}
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}
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if !keepEndOp {
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for len(sre.Sub) > 0 && sre.Sub[len(sre.Sub)-1].Op == syntax.OpEndText {
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sre.Sub = sre.Sub[:len(sre.Sub)-1]
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}
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}
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if len(sre.Sub) == 0 {
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return emptyRegexp
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}
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if len(sre.Sub) == 1 {
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return sre.Sub[0]
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}
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return sre
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case syntax.OpEmptyMatch:
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return emptyRegexp
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default:
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return sre
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}
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}
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// getSubstringLiteral returns regex part from sre surrounded by .+ or .* depending on the prefixSuffixOp.
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//
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// For example, if sre=".+foo.+" and prefixSuffix=syntax.OpPlus, then the function returns "foo".
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//
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// An empty string is returned if sre doesn't contain the given prefixSuffixOp prefix and suffix.
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func getSubstringLiteral(sre *syntax.Regexp, prefixSuffixOp syntax.Op) string {
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if sre.Op != syntax.OpConcat || len(sre.Sub) != 3 {
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return ""
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}
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if !isDotOp(sre.Sub[0], prefixSuffixOp) || !isDotOp(sre.Sub[2], prefixSuffixOp) {
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return ""
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}
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v, ok := getLiteral(sre.Sub[1])
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if !ok {
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return ""
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}
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return v
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}
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func isDotOp(sre *syntax.Regexp, op syntax.Op) bool {
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if sre.Op != op {
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return false
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}
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return sre.Sub[0].Op == syntax.OpAnyChar
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}
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var emptyRegexp = &syntax.Regexp{
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Op: syntax.OpEmptyMatch,
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}
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func parseRegexp(expr string) (*syntax.Regexp, error) {
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return syntax.Parse(expr, syntax.Perl|syntax.DotNL)
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}
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func mustParseRegexp(expr string) *syntax.Regexp {
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sre, err := parseRegexp(expr)
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if err != nil {
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panic(fmt.Errorf("BUG: cannot parse already verified regexp %q: %w", expr, err))
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}
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return sre
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}
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