diff --git a/cartographer/io/in_memory_proto_stream.cc b/cartographer/io/in_memory_proto_stream.cc
new file mode 100644
index 0000000..0773472
--- /dev/null
+++ b/cartographer/io/in_memory_proto_stream.cc
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2018 The Cartographer Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "cartographer/io/in_memory_proto_stream.h"
+
+namespace cartographer {
+namespace io {
+
+bool InMemoryProtoStreamReader::ReadProto(google::protobuf::Message* proto) {
+  if (eof()) return false;
+  proto->CopyFrom(*map_chunks_.front());
+  map_chunks_.pop();
+  return true;
+}
+
+}  // namespace io
+}  // namespace cartographer
diff --git a/cartographer/io/in_memory_proto_stream.h b/cartographer/io/in_memory_proto_stream.h
new file mode 100644
index 0000000..ced89d3
--- /dev/null
+++ b/cartographer/io/in_memory_proto_stream.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright 2018 The Cartographer Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef CARTOGRAPHER_IO_IN_MEMORY_PROTO_STREAM_H_
+#define CARTOGRAPHER_IO_IN_MEMORY_PROTO_STREAM_H_
+
+#include <queue>
+
+#include "cartographer/common/make_unique.h"
+#include "cartographer/common/port.h"
+#include "cartographer/io/proto_stream_interface.h"
+#include "google/protobuf/message.h"
+
+namespace cartographer {
+namespace io {
+
+class InMemoryProtoStreamReader
+    : public cartographer::io::ProtoStreamReaderInterface {
+ public:
+  explicit InMemoryProtoStreamReader(
+      std::queue<std::unique_ptr<google::protobuf::Message>>&& map_chunks)
+      : map_chunks_(std::move(map_chunks)){};
+  InMemoryProtoStreamReader() = default;
+  ~InMemoryProtoStreamReader() = default;
+
+  InMemoryProtoStreamReader(const InMemoryProtoStreamReader&) = delete;
+  InMemoryProtoStreamReader& operator=(const InMemoryProtoStreamReader&) =
+      delete;
+
+  template <typename MessageType>
+  void AddProto(const MessageType& proto) {
+    map_chunks_.push(common::make_unique<MessageType>(proto));
+  }
+
+  bool ReadProto(google::protobuf::Message* proto) override;
+  bool eof() const override { return map_chunks_.empty(); }
+
+ private:
+  std::queue<std::unique_ptr<google::protobuf::Message>> map_chunks_;
+};
+
+}  // namespace io
+}  // namespace cartographer
+
+#endif  // CARTOGRAPHER_IO_IN_MEMORY_PROTO_STREAM_H_
diff --git a/cartographer/io/in_memory_proto_stream_test.cc b/cartographer/io/in_memory_proto_stream_test.cc
new file mode 100644
index 0000000..f2ef8dc
--- /dev/null
+++ b/cartographer/io/in_memory_proto_stream_test.cc
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2018 The Cartographer Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "cartographer/io/in_memory_proto_stream.h"
+#include "cartographer/mapping/proto/pose_graph.pb.h"
+#include "cartographer/mapping/proto/serialization.pb.h"
+
+#include "gtest/gtest.h"
+
+namespace cartographer {
+namespace io {
+namespace {
+
+using common::make_unique;
+using google::protobuf::Message;
+using mapping::proto::PoseGraph;
+using mapping::proto::SerializedData;
+
+class InMemoryProtoStreamTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    pose_graph_.add_trajectory()->set_trajectory_id(1);
+    serialized_data_.mutable_odometry_data()->set_trajectory_id(2);
+  }
+
+  PoseGraph pose_graph_;
+  SerializedData serialized_data_;
+};
+
+TEST_F(InMemoryProtoStreamTest, ReadStreamInitializedFromQueue) {
+  std::queue<std::unique_ptr<Message>> proto_queue;
+  proto_queue.push(make_unique<PoseGraph>(pose_graph_));
+  proto_queue.push(make_unique<SerializedData>(serialized_data_));
+
+  InMemoryProtoStreamReader reader(std::move(proto_queue));
+
+  PoseGraph actual_pose_graph;
+  EXPECT_FALSE(reader.eof());
+  EXPECT_TRUE(reader.ReadProto(&actual_pose_graph));
+  EXPECT_EQ(1, actual_pose_graph.trajectory(0).trajectory_id());
+
+  SerializedData actual_serialized_data;
+  EXPECT_FALSE(reader.eof());
+  EXPECT_TRUE(reader.ReadProto(&actual_serialized_data));
+  EXPECT_EQ(2, actual_serialized_data.odometry_data().trajectory_id());
+
+  EXPECT_TRUE(reader.eof());
+}
+
+TEST_F(InMemoryProtoStreamTest, ReadStreamInitializedIncrementally) {
+  InMemoryProtoStreamReader reader;
+  reader.AddProto(pose_graph_);
+  reader.AddProto(serialized_data_);
+
+  PoseGraph actual_pose_graph;
+  EXPECT_FALSE(reader.eof());
+  EXPECT_TRUE(reader.ReadProto(&actual_pose_graph));
+  EXPECT_EQ(1, actual_pose_graph.trajectory(0).trajectory_id());
+
+  SerializedData actual_serialized_data;
+  EXPECT_FALSE(reader.eof());
+  EXPECT_TRUE(reader.ReadProto(&actual_serialized_data));
+  EXPECT_EQ(2, actual_serialized_data.odometry_data().trajectory_id());
+
+  EXPECT_TRUE(reader.eof());
+}
+
+}  // namespace
+}  // namespace io
+}  // namespace cartographer