[Feature] Support serialization for smart pointer (dmlc#1291)

* fix script

* t

* fix weird bugs

* fix

* fix

* upload

* fix

* fix

* lint

* fix

include/dgl/runtime/serializer.h

@@ -15,29 +15,29 @@
 namespace dmlc {
 namespace serializer {
 
-template<>
+template <>
 struct Handler<DLDataType> {
-  inline static void Write(Stream *strm, const DLDataType& dtype) {
+  inline static void Write(Stream *strm, const DLDataType &dtype) {
     Handler<uint8_t>::Write(strm, dtype.code);
     Handler<uint8_t>::Write(strm, dtype.bits);
     Handler<uint16_t>::Write(strm, dtype.lanes);
   }
-  inline static bool Read(Stream *strm, DLDataType* dtype) {
+  inline static bool Read(Stream *strm, DLDataType *dtype) {
     if (!Handler<uint8_t>::Read(strm, &(dtype->code))) return false;
     if (!Handler<uint8_t>::Read(strm, &(dtype->bits))) return false;
     if (!Handler<uint16_t>::Read(strm, &(dtype->lanes))) return false;
     return true;
   }
 };
 
-template<>
+template <>
 struct Handler<DLContext> {
-  inline static void Write(Stream *strm, const DLContext& ctx) {
+  inline static void Write(Stream *strm, const DLContext &ctx) {
     int32_t device_type = static_cast<int32_t>(ctx.device_type);
     Handler<int32_t>::Write(strm, device_type);
     Handler<int32_t>::Write(strm, ctx.device_id);
   }
-  inline static bool Read(Stream *strm, DLContext* ctx) {
+  inline static bool Read(Stream *strm, DLContext *ctx) {
     int32_t device_type = 0;
     if (!Handler<int32_t>::Read(strm, &(device_type))) return false;
     ctx->device_type = static_cast<DLDeviceType>(device_type);

include/dgl/runtime/smart_ptr_serializer.h

@@ -0,0 +1,51 @@
+/*!
+ *  Copyright (c) 2017 by Contributors
+ * \file dgl/runtime/serializer.h
+ * \brief Serializer extension to support DGL data types
+ *  Include this file to enable serialization of DLDataType, DLContext
+ */
+#ifndef DGL_RUNTIME_SMART_PTR_SERIALIZER_H_
+#define DGL_RUNTIME_SMART_PTR_SERIALIZER_H_
+
+#include <dmlc/io.h>
+#include <dmlc/serializer.h>
+
+namespace dmlc {
+namespace serializer {
+
+//! \cond Doxygen_Suppress
+template <typename T>
+struct Handler<std::shared_ptr<T>> {
+  inline static void Write(Stream *strm, const std::shared_ptr<T> &data) {
+    Handler<T>::Write(strm, *data.get());
+  }
+  inline static bool Read(Stream *strm, std::shared_ptr<T> *data) {
+    // When read, the default initialization behavior of shared_ptr is
+    // shared_ptr<T>(), which is holding a nullptr. Here we need to manually
+    // reset to a real object for further loading
+    if (!(*data)) {
+      data->reset(new T());
+    }
+    return Handler<T>::Read(strm, data->get());
+  }
+};
+
+template <typename T>
+struct Handler<std::unique_ptr<T>> {
+  inline static void Write(Stream *strm, const std::unique_ptr<T> &data) {
+    Handler<T>::Write(strm, *data.get());
+  }
+  inline static bool Read(Stream *strm, std::unique_ptr<T> *data) {
+    // When read, the default initialization behavior of unique_ptr is
+    // unique_ptr<T>(), which is holding a nullptr. Here we need to manually
+    // reset to a real object for further loading
+    if (!(*data)) {
+      data->reset(new T());
+    }
+    return Handler<T>::Read(strm, data->get());
+  }
+};
+
+}  // namespace serializer
+}  // namespace dmlc
+#endif  // DGL_RUNTIME_SMART_PTR_SERIALIZER_H_

tests/cpp/test_smart_ptr_serialize.cc

@@ -0,0 +1,103 @@
+#include <dgl/runtime/serializer.h>
+#include <dgl/runtime/smart_ptr_serializer.h>
+#include <dmlc/io.h>
+#include <dmlc/logging.h>
+#include <dmlc/memory_io.h>
+#include <dmlc/parameter.h>
+#include <gtest/gtest.h>
+#include <cstring>
+#include <iostream>
+#include <sstream>
+#include <unordered_map>
+
+using namespace std;
+
+class MyClass {
+ public:
+  MyClass() {}
+  MyClass(std::string data) : data_(data) {}
+  inline void Save(dmlc::Stream *strm) const { strm->Write(this->data_); }
+  inline bool Load(dmlc::Stream *strm) { return strm->Read(&data_); }
+  inline bool operator==(const MyClass &other) const {
+    return data_ == other.data_;
+  }
+
+ public:
+  std::string data_;
+};
+// need to declare the traits property of my class to dmlc
+namespace dmlc {
+DMLC_DECLARE_TRAITS(has_saveload, MyClass, true);
+}
+
+template <typename T>
+class SmartPtrTest : public ::testing::Test {
+ public:
+  typedef T SmartPtr;
+};
+
+using SmartPtrTypes =
+    ::testing::Types<std::shared_ptr<MyClass>, std::unique_ptr<MyClass>>;
+TYPED_TEST_SUITE(SmartPtrTest, SmartPtrTypes);
+
+TYPED_TEST(SmartPtrTest, Obj_Test) {
+  std::string blob;
+  dmlc::MemoryStringStream fs(&blob);
+  using SmartPtr = typename TestFixture::SmartPtr;
+  auto myc = SmartPtr(new MyClass("1111"));
+  { static_cast<dmlc::Stream *>(&fs)->Write(myc); }
+  fs.Seek(0);
+  auto copy_data = SmartPtr(new MyClass());
+  CHECK(static_cast<dmlc::Stream *>(&fs)->Read(&copy_data));
+
+  EXPECT_EQ(myc->data_, copy_data->data_);
+}
+
+TYPED_TEST(SmartPtrTest, Vector_Test1) {
+  std::string blob;
+  dmlc::MemoryStringStream fs(&blob);
+  using SmartPtr = typename TestFixture::SmartPtr;
+  typedef std::pair<std::string, SmartPtr> Pair;
+  auto my1 = SmartPtr(new MyClass("@A@"));
+  auto my2 = SmartPtr(new MyClass("2222"));
+
+  std::vector<Pair> myclasses;
+  myclasses.emplace_back("a", SmartPtr(new MyClass("@A@B")));
+  myclasses.emplace_back("b", SmartPtr(new MyClass("2222")));
+  static_cast<dmlc::Stream *>(&fs)->Write<std::vector<Pair>>(myclasses);
+
+  dmlc::MemoryStringStream ofs(&blob);
+  std::vector<Pair> copy_myclasses;
+  static_cast<dmlc::Stream *>(&ofs)->Read<std::vector<Pair>>(&copy_myclasses);
+
+  EXPECT_TRUE(std::equal(myclasses.begin(), myclasses.end(),
+                         copy_myclasses.begin(),
+                         [](const Pair &left, const Pair &right) {
+                           return (left.second->data_ == right.second->data_) &&
+                                  (left.first == right.first);
+                         }));
+}
+
+TYPED_TEST(SmartPtrTest, Vector_Test2) {
+  std::string blob;
+  dmlc::MemoryStringStream fs(&blob);
+  using SmartPtr = typename TestFixture::SmartPtr;
+  auto my1 = SmartPtr(new MyClass("@A@"));
+  auto my2 = SmartPtr(new MyClass("2222"));
+
+  std::vector<SmartPtr> myclasses;
+  myclasses.emplace_back(new MyClass("@A@"));
+  myclasses.emplace_back(new MyClass("2222"));
+  static_cast<dmlc::Stream *>(&fs)->Write<std::vector<SmartPtr>>(myclasses);
+
+  dmlc::MemoryStringStream ofs(&blob);
+  std::vector<SmartPtr> copy_myclasses;
+  static_cast<dmlc::Stream *>(&ofs)->Read<std::vector<SmartPtr>>(
+      &copy_myclasses);
+
+  EXPECT_TRUE(std::equal(myclasses.begin(), myclasses.end(),
+                         copy_myclasses.begin(),
+                         [](const SmartPtr &left, const SmartPtr &right) {
+                           return left->data_ == right->data_;
+                         }));
+}