Patch internal change 111557819.

Defer calls to mutable_unknown_fields() until it is actually required to
save memory for C++ lite runtime.

Change-Id: Ica9c1fd276cdb164942d1e7b6e098c83ee3ffdc5

4 files changed, 74 insertions, 0 deletions

diff --git a/src/google/protobuf/io/coded_stream.cc b/src/google/protobuf/io/coded_stream.cc
index 4bcd354f..e3a34d0a 100644
--- a/src/google/protobuf/io/coded_stream.cc
+++ b/src/google/protobuf/io/coded_stream.cc
@@ -629,6 +629,24 @@ CodedOutputStream::CodedOutputStream(ZeroCopyOutputStream* output)
   had_error_ = false;
 }
 
+CodedOutputStream::CodedOutputStream(ZeroCopyOutputStream* output,
+                                     bool do_eager_refresh)
+  : output_(output),
+    buffer_(NULL),
+    buffer_size_(0),
+    total_bytes_(0),
+    had_error_(false),
+    aliasing_enabled_(false) {
+  if (do_eager_refresh) {
+    // Eagerly Refresh() so buffer space is immediately available.
+    Refresh();
+    // The Refresh() may have failed. If the client doesn't write any data,
+    // though, don't consider this an error. If the client does write data, then
+    // another Refresh() will be attempted and it will set the error once again.
+    had_error_ = false;
+  }
+}
+
 CodedOutputStream::~CodedOutputStream() {
   Trim();
 }
diff --git a/src/google/protobuf/io/coded_stream.h b/src/google/protobuf/io/coded_stream.h
index 2da096c5..020f20c7 100644
--- a/src/google/protobuf/io/coded_stream.h
+++ b/src/google/protobuf/io/coded_stream.h
@@ -666,6 +666,7 @@ class LIBPROTOBUF_EXPORT CodedOutputStream {
  public:
   // Create an CodedOutputStream that writes to the given ZeroCopyOutputStream.
   explicit CodedOutputStream(ZeroCopyOutputStream* output);
+  CodedOutputStream(ZeroCopyOutputStream* output, bool do_eager_refresh);
 
   // Destroy the CodedOutputStream and position the underlying
   // ZeroCopyOutputStream immediately after the last byte written.
diff --git a/src/google/protobuf/io/zero_copy_stream_impl_lite.cc b/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
index 686e63f2..083beca4 100644
--- a/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
+++ b/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
@@ -157,6 +157,7 @@ StringOutputStream::~StringOutputStream() {
 }
 
 bool StringOutputStream::Next(void** data, int* size) {
+  GOOGLE_CHECK_NE(NULL, target_);
   int old_size = target_->size();
 
   // Grow the string.
@@ -188,14 +189,44 @@ bool StringOutputStream::Next(void** data, int* size) {
 
 void StringOutputStream::BackUp(int count) {
   GOOGLE_CHECK_GE(count, 0);
+  GOOGLE_CHECK_NE(NULL, target_);
   GOOGLE_CHECK_LE(count, target_->size());
   target_->resize(target_->size() - count);
 }
 
 int64 StringOutputStream::ByteCount() const {
+  GOOGLE_CHECK_NE(NULL, target_);
   return target_->size();
 }
 
+void StringOutputStream::SetString(string* target) {
+  target_ = target;
+}
+
+// ===================================================================
+
+LazyStringOutputStream::LazyStringOutputStream(
+    ResultCallback<string*>* callback)
+    : StringOutputStream(NULL),
+      callback_(GOOGLE_CHECK_NOTNULL(callback)),
+      string_is_set_(false) {
+}
+
+LazyStringOutputStream::~LazyStringOutputStream() {
+}
+
+bool LazyStringOutputStream::Next(void** data, int* size) {
+  if (!string_is_set_) {
+    SetString(callback_->Run());
+    string_is_set_ = true;
+  }
+  return StringOutputStream::Next(data, size);
+}
+
+int64 LazyStringOutputStream::ByteCount() const {
+  return string_is_set_ ? StringOutputStream::ByteCount() : 0;
+}
+
 // ===================================================================
 
 CopyingInputStream::~CopyingInputStream() {}
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());