Merge v1.2.1-master

Signed-off-by: Emile Vauge <emile@vauge.com>

vendor/github.com/prometheus/common/expfmt/text_create.go

@@ -14,7 +14,6 @@
 package expfmt
 
 import (
-	"bytes"
 	"fmt"
 	"io"
 	"math"
@@ -26,9 +25,12 @@ import (
 
 // MetricFamilyToText converts a MetricFamily proto message into text format and
 // writes the resulting lines to 'out'. It returns the number of bytes written
-// and any error encountered.  This function does not perform checks on the
-// content of the metric and label names, i.e. invalid metric or label names
+// and any error encountered. The output will have the same order as the input,
+// no further sorting is performed. Furthermore, this function assumes the input
+// is already sanitized and does not perform any sanity checks. If the input
+// contains duplicate metrics or invalid metric or label names, the conversion
 // will result in invalid text format output.
+//
 // This method fulfills the type 'prometheus.encoder'.
 func MetricFamilyToText(out io.Writer, in *dto.MetricFamily) (int, error) {
 	var written int
@@ -285,21 +287,17 @@ func labelPairsToText(
 	return written, nil
 }
 
+var (
+	escape                = strings.NewReplacer("\\", `\\`, "\n", `\n`)
+	escapeWithDoubleQuote = strings.NewReplacer("\\", `\\`, "\n", `\n`, "\"", `\"`)
+)
+
 // escapeString replaces '\' by '\\', new line character by '\n', and - if
 // includeDoubleQuote is true - '"' by '\"'.
 func escapeString(v string, includeDoubleQuote bool) string {
-	result := bytes.NewBuffer(make([]byte, 0, len(v)))
-	for _, c := range v {
-		switch {
-		case c == '\\':
-			result.WriteString(`\\`)
-		case includeDoubleQuote && c == '"':
-			result.WriteString(`\"`)
-		case c == '\n':
-			result.WriteString(`\n`)
-		default:
-			result.WriteRune(c)
-		}
+	if includeDoubleQuote {
+		return escapeWithDoubleQuote.Replace(v)
 	}
-	return result.String()
+
+	return escape.Replace(v)
 }