@@ -11,7 +11,7 @@ import (

 	"time"

 	"github.com/docker/docker/pkg/ioutils"

-	"github.com/docker/docker/pkg/stringutils"

+	"github.com/docker/docker/pkg/stringid"

 )

 // Installer is a standard interface for objects which can "install" themselves

@@ -78,7 +78,7 @@ func (eng *Engine) RegisterCatchall(catchall Handler) {

 func New() *Engine {

 	eng := &Engine{

 		handlers: make(map[string]Handler),

-		id:       stringutils.GenerateRandomString(),

+		id:       stringid.GenerateRandomID(),

 		Stdout:   os.Stdout,

 		Stderr:   os.Stderr,

 		Stdin:    os.Stdin,

@@ -1,23 +1,10 @@

 package stringutils

 import (

-	"crypto/rand"

-	"encoding/hex"

-	"io"

 	mathrand "math/rand"

 	"time"

 )

-// Generate 32 chars random string

-func GenerateRandomString() string {

-	id := make([]byte, 32)

-

-	if _, err := io.ReadFull(rand.Reader, id); err != nil {

-		panic(err) // This shouldn't happen

-	}

-	return hex.EncodeToString(id)

-}

-

 // Generate alpha only random stirng with length n

 func GenerateRandomAlphaOnlyString(n int) string {

 	// make a really long string

@@ -2,18 +2,19 @@ package stringutils

 import "testing"

-func TestRandomString(t *testing.T) {

-	str := GenerateRandomString()

-	if len(str) != 64 {

-		t.Fatalf("Id returned is incorrect: %s", str)

+func testLengthHelper(generator func(int) string, t *testing.T) {

+	expectedLength := 20

+	s := generator(expectedLength)

+	if len(s) != expectedLength {

+		t.Fatalf("Length of %s was %d but expected length %d", s, len(s), expectedLength)

 	}

 }

-func TestRandomStringUniqueness(t *testing.T) {

+func testUniquenessHelper(generator func(int) string, t *testing.T) {

 	repeats := 25

 	set := make(map[string]struct{}, repeats)

 	for i := 0; i < repeats; i = i + 1 {

-		str := GenerateRandomString()

+		str := generator(64)

 		if len(str) != 64 {

 			t.Fatalf("Id returned is incorrect: %s", str)

 		}

@@ -23,3 +24,35 @@ func TestRandomStringUniqueness(t *testing.T) {

 		set[str] = struct{}{}

 	}

 }

+

+func isASCII(s string) bool {

+	for _, c := range s {

+		if c > 127 {

+			return false

+		}

+	}

+	return true

+}

+

+func TestGenerateRandomAlphaOnlyStringLength(t *testing.T) {

+	testLengthHelper(GenerateRandomAlphaOnlyString, t)

+}

+

+func TestGenerateRandomAlphaOnlyStringUniqueness(t *testing.T) {

+	testUniquenessHelper(GenerateRandomAlphaOnlyString, t)

+}

+

+func TestGenerateRandomAsciiStringLength(t *testing.T) {

+	testLengthHelper(GenerateRandomAsciiString, t)

+}

+

+func TestGenerateRandomAsciiStringUniqueness(t *testing.T) {

+	testUniquenessHelper(GenerateRandomAsciiString, t)

+}

+

+func TestGenerateRandomAsciiStringIsAscii(t *testing.T) {

+	str := GenerateRandomAsciiString(64)

+	if !isASCII(str) {

+		t.Fatalf("%s contained non-ascii characters", str)

+	}

+}

@@ -24,7 +24,7 @@ import (

 	"github.com/docker/docker/pkg/fileutils"

 	"github.com/docker/docker/pkg/ioutils"

 	"github.com/docker/docker/pkg/jsonmessage"

-	"github.com/docker/docker/pkg/stringutils"

+	"github.com/docker/docker/pkg/stringid"

 )

 type KeyValuePair struct {

@@ -313,7 +313,7 @@ var globalTestID string

 // new directory.

 func TestDirectory(templateDir string) (dir string, err error) {

 	if globalTestID == "" {

-		globalTestID = stringutils.GenerateRandomString()[:4]

+		globalTestID = stringid.GenerateRandomID()[:4]

 	}

 	prefix := fmt.Sprintf("docker-test%s-%s-", globalTestID, GetCallerName(2))

 	if prefix == "" {