Add vendoring

vendor/github.com/VictoriaMetrics/metrics/validator.go

@@ -0,0 +1,94 @@
+package metrics
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+// ValidateMetric validates provided string
+// to be valid Prometheus-compatible metric with possible labels.
+// For instance,
+//
+//   - foo
+//   - foo{bar="baz"}
+//   - foo{bar="baz",aaa="b"}
+func ValidateMetric(s string) error {
+	if len(s) == 0 {
+		return fmt.Errorf("metric cannot be empty")
+	}
+	if strings.IndexByte(s, '\n') >= 0 {
+		return fmt.Errorf("metric cannot contain line breaks")
+	}
+	n := strings.IndexByte(s, '{')
+	if n < 0 {
+		return validateIdent(s)
+	}
+	ident := s[:n]
+	s = s[n+1:]
+	if err := validateIdent(ident); err != nil {
+		return err
+	}
+	if len(s) == 0 || s[len(s)-1] != '}' {
+		return fmt.Errorf("missing closing curly brace at the end of %q", ident)
+	}
+	return validateTags(s[:len(s)-1])
+}
+
+func validateTags(s string) error {
+	if len(s) == 0 {
+		return nil
+	}
+	for {
+		n := strings.IndexByte(s, '=')
+		if n < 0 {
+			return fmt.Errorf("missing `=` after %q", s)
+		}
+		ident := s[:n]
+		s = s[n+1:]
+		if err := validateIdent(ident); err != nil {
+			return err
+		}
+		if len(s) == 0 || s[0] != '"' {
+			return fmt.Errorf("missing starting `\"` for %q value; tail=%q", ident, s)
+		}
+		s = s[1:]
+	again:
+		n = strings.IndexByte(s, '"')
+		if n < 0 {
+			return fmt.Errorf("missing trailing `\"` for %q value; tail=%q", ident, s)
+		}
+		m := n
+		for m > 0 && s[m-1] == '\\' {
+			m--
+		}
+		if (n-m)%2 == 1 {
+			s = s[n+1:]
+			goto again
+		}
+		s = s[n+1:]
+		if len(s) == 0 {
+			return nil
+		}
+		if !strings.HasPrefix(s, ",") {
+			return fmt.Errorf("missing `,` after %q value; tail=%q", ident, s)
+		}
+		s = skipSpace(s[1:])
+	}
+}
+
+func skipSpace(s string) string {
+	for len(s) > 0 && s[0] == ' ' {
+		s = s[1:]
+	}
+	return s
+}
+
+func validateIdent(s string) error {
+	if !identRegexp.MatchString(s) {
+		return fmt.Errorf("invalid identifier %q", s)
+	}
+	return nil
+}
+
+var identRegexp = regexp.MustCompile("^[a-zA-Z_:.][a-zA-Z0-9_:.]*$")