stastd_exporter speed up

x.diff

diff --git a/exporter.go b/exporter.go
index 15c01b7..c225fcf 100644
--- a/exporter.go
+++ b/exporter.go
@@ -21,7 +21,6 @@ import (
        "hash/fnv"
        "io"
        "net"
-       "regexp"
        "sort"
        "strconv"
        "strings"
@@ -44,8 +43,6 @@ const (
 )

 var (
-       illegalCharsRE = regexp.MustCompile(`[^a-zA-Z0-9_]`)
-
        hash   = fnv.New64a()
        strBuf bytes.Buffer // Used for hashing.
        intBuf = make([]byte, 8)
@@ -284,9 +281,21 @@ func escapeMetricName(metricName string) string {
                metricName = "_" + metricName
        }

-       // Replace all illegal metric chars with underscores.
-       metricName = illegalCharsRE.ReplaceAllString(metricName, "_")
-       return metricName
+       out := make([]byte, len(metricName))
+       j := 0
+       for _, c := range metricName {
+               if (c >= 'a' && c <= 'z') ||
+                       (c >= 'A' && c <= 'Z') ||
+                       (c >= '0' && c <= '9') {
+                       out[j] = byte(c)
+               } else {
+                       out[j] = byte('_')
+               }
+               j++
+       }
+
+       return string(out[:j])
+
 }

 // Listen handles all events sent to the given channel sequentially. It