Add support for decoding a stream of JSON objects.

Signed-off-by: David Symonds <dsymonds@golang.org>

jsonpb/jsonpb.go

diff --git a/jsonpb/jsonpb.go b/jsonpb/jsonpb.go
index 768564e..a9e778c 100644
--- a/jsonpb/jsonpb.go
+++ b/jsonpb/jsonpb.go
@@ -428,15 +428,23 @@
 	return out.err
 }
 
+// UnmarshalNext unmarshals the next protocol buffer from a JSON object stream.
+// This function is lenient and will decode any options permutations of the
+// related Marshaler.
+func UnmarshalNext(dec *json.Decoder, pb proto.Message) error {
+	inputValue := json.RawMessage{}
+	if err := dec.Decode(&inputValue); err != nil {
+		return err
+	}
+	return unmarshalValue(reflect.ValueOf(pb).Elem(), inputValue)
+}
+
 // Unmarshal unmarshals a JSON object stream into a protocol
 // buffer. This function is lenient and will decode any options
 // permutations of the related Marshaler.
 func Unmarshal(r io.Reader, pb proto.Message) error {
-	inputValue := json.RawMessage{}
-	if err := json.NewDecoder(r).Decode(&inputValue); err != nil {
-		return err
-	}
-	return unmarshalValue(reflect.ValueOf(pb).Elem(), inputValue)
+	dec := json.NewDecoder(r)
+	return UnmarshalNext(dec, pb)
 }
 
 // UnmarshalString will populate the fields of a protocol buffer based

jsonpb/jsonpb_test.go

diff --git a/jsonpb/jsonpb_test.go b/jsonpb/jsonpb_test.go
index 3d70b87..c04da85 100644
--- a/jsonpb/jsonpb_test.go
+++ b/jsonpb/jsonpb_test.go
@@ -32,6 +32,9 @@
 package jsonpb
 
 import (
+	"bytes"
+	"encoding/json"
+	"io"
 	"reflect"
 	"testing"
 
@@ -415,6 +418,39 @@
 	}
 }
 
+func TestUnmarshalNext(t *testing.T) {
+	// Create a buffer with many concatenated JSON objects.
+	var b bytes.Buffer
+	for _, tt := range unmarshalingTests {
+		b.WriteString(tt.json)
+	}
+
+	dec := json.NewDecoder(&b)
+	for _, tt := range unmarshalingTests {
+		// Make a new instance of the type of our expected object.
+		p := reflect.New(reflect.TypeOf(tt.pb).Elem()).Interface().(proto.Message)
+
+		err := UnmarshalNext(dec, p)
+		if err != nil {
+			t.Errorf("%s: %v", tt.desc, err)
+			continue
+		}
+
+		// For easier diffs, compare text strings of the protos.
+		exp := proto.MarshalTextString(tt.pb)
+		act := proto.MarshalTextString(p)
+		if string(exp) != string(act) {
+			t.Errorf("%s: got [%s] want [%s]", tt.desc, act, exp)
+		}
+	}
+
+	p := &pb.Simple{}
+	err := UnmarshalNext(dec, p)
+	if err != io.EOF {
+		t.Errorf("eof: got %v, expected io.EOF", err)
+	}
+}
+
 var unmarshalingShouldError = []struct {
 	desc string
 	in   string