1 files changed, 24 insertions, 0 deletions
diff --git a/src/google/protobuf/io/zero_copy_stream_impl_lite.h b/src/google/protobuf/io/zero_copy_stream_impl_lite.h
index a598ef2e..1c397dea 100644
--- a/src/google/protobuf/io/zero_copy_stream_impl_lite.h
+++ b/src/google/protobuf/io/zero_copy_stream_impl_lite.h
@@ -148,6 +148,9 @@ class LIBPROTOBUF_EXPORT StringOutputStream : public ZeroCopyOutputStream {
   void BackUp(int count);
   int64 ByteCount() const;
 
+ protected:
+  void SetString(string* target);
+
  private:
   static const int kMinimumSize = 16;
 
@@ -156,6 +159,27 @@ class LIBPROTOBUF_EXPORT StringOutputStream : public ZeroCopyOutputStream {
   GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StringOutputStream);
 };
 
+// LazyStringOutputStream is a StringOutputStream with lazy acquisition of
+// the output string from a callback. The string is owned externally, and not
+// deleted in the stream destructor.
+class LIBPROTOBUF_EXPORT LazyStringOutputStream : public StringOutputStream {
+ public:
+  // Callback should be permanent (non-self-deleting). Ownership is transferred
+  // to the LazyStringOutputStream.
+  explicit LazyStringOutputStream(ResultCallback<string*>* callback);
+  ~LazyStringOutputStream();
+
+  // implements ZeroCopyOutputStream, overriding StringOutputStream -----------
+  bool Next(void** data, int* size);
+  int64 ByteCount() const;
+
+ private:
+  const scoped_ptr<ResultCallback<string*> > callback_;
+  bool string_is_set_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(LazyStringOutputStream);
+};
+
 // Note:  There is no StringInputStream.  Instead, just create an
 // ArrayInputStream as follows:
 //   ArrayInputStream input(str.data(), str.size());