goprotobuf: Serialize extensions in a consistent order.
R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/6883047
diff --git a/proto/all_test.go b/proto/all_test.go
index 5024905..9f63d7c 100644
--- a/proto/all_test.go
+++ b/proto/all_test.go
@@ -1457,6 +1457,35 @@
}
}
+func TestExtensionMarshalOrder(t *testing.T) {
+ m := &MyMessage{Count: Int32(123)}
+ if err := SetExtension(m, E_Ext_More, &Ext{Data: String("alpha")}); err != nil {
+ t.Fatalf("SetExtension: %v", err)
+ }
+ if err := SetExtension(m, E_Ext_Text, String("aleph")); err != nil {
+ t.Fatalf("SetExtension: %v", err)
+ }
+ if err := SetExtension(m, E_Ext_Number, Int32(1)); err != nil {
+ t.Fatalf("SetExtension: %v", err)
+ }
+
+ // Serialize m several times, and check we get the same bytes each time.
+ var orig []byte
+ for i := 0; i < 10; i++ {
+ b, err := Marshal(m)
+ if err != nil {
+ t.Fatalf("Marshal: %v", err)
+ }
+ if i == 0 {
+ orig = b
+ continue
+ }
+ if !bytes.Equal(b, orig) {
+ t.Errorf("Bytes differ on attempt #%d", i)
+ }
+ }
+}
+
func fuzzUnmarshal(t *testing.T, data []byte) {
defer func() {
if e := recover(); e != nil {
diff --git a/proto/encode.go b/proto/encode.go
index 288fb9c..8ba3935 100644
--- a/proto/encode.go
+++ b/proto/encode.go
@@ -38,6 +38,7 @@
import (
"errors"
"reflect"
+ "sort"
)
// ErrRequiredNotSet is the error returned if Marshal is called with
@@ -545,8 +546,23 @@
if err := encodeExtensionMap(v); err != nil {
return err
}
- for _, e := range v {
- o.buf = append(o.buf, e.enc...)
+ // Fast-path for common cases: zero or one extensions.
+ if len(v) <= 1 {
+ for _, e := range v {
+ o.buf = append(o.buf, e.enc...)
+ }
+ return nil
+ }
+
+ // Sort keys to provide a deterministic encoding.
+ keys := make([]int, 0, len(v))
+ for k := range v {
+ keys = append(keys, int(k))
+ }
+ sort.Ints(keys)
+
+ for _, k := range keys {
+ o.buf = append(o.buf, v[int32(k)].enc...)
}
return nil
}