tls/status -- make stubs add warning and status randomly

helpers.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"math/rand"
 	"net"
 	"net/http"
 	"os"
@@ -235,6 +236,34 @@ func checkPacketPortAvailable(host string, port int) error {
 	return err
 }
 
+// ------------------------
+// random string generation
+// ------------------------
+const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+const (
+	letterIdxBits = 6                    // 6 bits to represent a letter index
+	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
+	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
+)
+
+func RandStringBytesMaskImpr(n int) string {
+	b := make([]byte, n)
+	// A rand.Int63() generates 63 random bits, enough for letterIdxMax letters!
+	for i, cache, remain := n-1, rand.Int63(), letterIdxMax; i >= 0; {
+		if remain == 0 {
+			cache, remain = rand.Int63(), letterIdxMax
+		}
+		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
+			b[i] = letterBytes[idx]
+			i--
+		}
+		cache >>= letterIdxBits
+		remain--
+	}
+
+	return string(b)
+}
+
 // ---------------------
 // debug logging helpers
 // ---------------------