Add LwwRegister CRDT

blimp/helium/syncable_primitive_serializer.cc

Index: blimp/helium/syncable_primitive_serializer.cc
diff --git a/blimp/helium/syncable_primitive_serializer.cc b/blimp/helium/syncable_primitive_serializer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..4840d41e19b549d5a0b92fa4344fb9620c45b7da
--- /dev/null
+++ b/blimp/helium/syncable_primitive_serializer.cc
@@ -0,0 +1,55 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "blimp/helium/syncable_primitive_serializer.h"
+
+#include <stdint.h>
+
+#include <string>
+
+#include "third_party/protobuf/src/google/protobuf/io/coded_stream.h"
+
+namespace blimp {
+namespace helium {
+namespace {
+constexpr uint32_t kMaxStringLength = (10 << 20);  // 10MB

[scf, 2016/10/19 17:23:03]

move this to common? i will probably need something similar in USet

+}
+
+// -----------------------------
+// int32_t serialization methods
+
+void SyncablePrimitiveSerializer::Serialize(
+    const int32_t& value,
+    google::protobuf::io::CodedOutputStream* output_stream) {
+  output_stream->WriteVarint32(static_cast<uint32_t>(value));
+}
+
+bool SyncablePrimitiveSerializer::Deserialize(
+    google::protobuf::io::CodedInputStream* input_stream,
+    int32_t* value) {
+  return input_stream->ReadVarint32(reinterpret_cast<uint32_t*>(value));
+}
+
+// ---------------------------------
+// std::string serialization methods
+
+void SyncablePrimitiveSerializer::Serialize(
+    const std::string& value,
+    google::protobuf::io::CodedOutputStream* output_stream) {
+  output_stream->WriteVarint32(value.length());
+  output_stream->WriteString(value);
+}
+
+bool SyncablePrimitiveSerializer::Deserialize(
+    google::protobuf::io::CodedInputStream* input_stream,
+    std::string* value) {
+  uint32_t length;
+  if (input_stream->ReadVarint32(&length) && length < kMaxStringLength) {

[scf, 2016/10/19 17:23:03]

ideally the kMaxStringLength case would be detected at the serializer side. and
probably failing serialization. here in the deserialization you already sent the
data across the wire and are leaving the stream cursor in a invalid state.

[steimel, 2016/10/19 17:37:54]

I agree, although in my mind this is more of a sanity check that the data isn't
corrupt. One doubt I have about failing on Serialization is that AFAIK we were
assuming serialization couldn't fail (I could be wrong on this). I'm sure Kevin
has some thoughts on this.

[Kevin M, 2016/10/19 17:49:11]

Yup! This is more about validating the payload contents than the payload size
itself.
You are correct that serialization shouldn't fail, but this code is failing on
deserialization. 

[scf, 2016/10/19 18:08:26]

I think the size limit should rarely happen, and in case it happens most likely
something is corrupt, which I think we should fail during serialization. 

+    return input_stream->ReadString(value, length);
+  }
+  return false;
+}
+
+}  // namespace helium
+}  // namespace blimp