Adding search and replace regexp utils

utils/coreutils.go

@@ -225,3 +225,26 @@ func ParseZeroRatingSubject(rateSubj string) (time.Duration, error) {
 	durStr := rateSubj[len(ZERO_RATING_SUBJECT_PREFIX):]
 	return time.ParseDuration(durStr)
 }
+
+// Used to parse extra fields definition into regexp rules
+func ParseSearchReplaceRegexp(strRule string) (*regexp.Regexp, string, error) {
+	// String rule expected in the form ~hdr_name:s/match_rule/replace_rule/
+	getRuleRgxp := regexp.MustCompile(`:s\/(.+[^\\])\/(.+[^\\])\/`) // Make sure the separator / is not escaped in the rule
+	allMatches := getRuleRgxp.FindStringSubmatch(strRule)
+	if len(allMatches) != 3 { // Second and third groups are of interest to us
+		return nil, "", errors.New("Invalid Search&Replace rule.")
+	}
+	searchRegexp, err := regexp.Compile(allMatches[1])
+	if err != nil {
+		return nil, "", err
+	}
+	return searchRegexp, allMatches[2], nil
+}
+
+// Used to expand string sources, eg: extra fields
+func RegexpSearchReplace(src string, searchRl *regexp.Regexp, replaceTpl string) string {
+	res := []byte{}
+	match := searchRl.FindStringSubmatchIndex(src)
+	res = searchRl.ExpandString(res, replaceTpl, src, match)
+	return string(res)
+}