Mojo: more idiomatic C++ bindings

mojo/public/cpp/bindings/lib/array_serialization.h

+// Copyright 2014 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.
+
+#ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_ARRAY_SERIALIZATION_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_LIB_ARRAY_SERIALIZATION_H_
+
+#include <string>
+
+#include "mojo/public/cpp/bindings/lib/array_internal.h"
+#include "mojo/public/cpp/bindings/lib/string_serialization.h"
+
+namespace mojo {
+
+template <typename E>
+inline size_t GetSerializedSize_(const Array<E>& input);
+
+template <typename E, typename F>
+inline void Serialize_(Array<E> input, internal::Buffer* buf,
+                       internal::Array_Data<F>** output);
+template <typename E, typename F>
+inline void Deserialize_(internal::Array_Data<F>* data, Array<E>* output);
+
+namespace internal {
+
+template <typename E, typename F, bool move_only = IsMoveOnlyType<E>::value>
+struct ArraySerializer;
+
+template <typename E, typename F> struct ArraySerializer<E, F, false> {
+  MOJO_COMPILE_ASSERT(sizeof(E) == sizeof(F), wrong_array_serializer);
+  static size_t GetSerializedSize(const Array<E>& input) {
+    return sizeof(Array_Data<F>) + Align(input.size() * sizeof(E));
+  }
+  static void SerializeElements(
+      Array<E> input, Buffer* buf, Array_Data<F>* output) {
+    memcpy(output->storage(), &input.storage()[0], input.size() * sizeof(E));
+  }
+  static void DeserializeElements(
+      Array_Data<F>* input, Array<E>* output) {
+    std::vector<E> result(input->size());
+    memcpy(&result[0], input->storage(), input->size() * sizeof(E));
+    output->Swap(&result);
+  }
+};
+
+template <> struct ArraySerializer<bool, bool, false> {
+  static size_t GetSerializedSize(const Array<bool>& input) {
+    return sizeof(Array_Data<bool>) + Align((input.size() + 7) / 8);
+  }
+  static void SerializeElements(
+      Array<bool> input, Buffer* buf, Array_Data<bool>* output) {
+    // TODO(darin): Can this be a memcpy somehow instead of a bit-by-bit copy?
+    for (size_t i = 0; i < input.size(); ++i)
+      output->at(i) = input[i];
+  }
+  static void DeserializeElements(
+      Array_Data<bool>* input, Array<bool>* output) {
+    Array<bool> result(input->size());
+    // TODO(darin): Can this be a memcpy somehow instead of a bit-by-bit copy?
+    for (size_t i = 0; i < input->size(); ++i)
+      result.at(i) = input->at(i);
+    output->Swap(&result);
+  }
+};
+
+template <typename H> struct ArraySerializer<ScopedHandleBase<H>, H, true> {
+  static size_t GetSerializedSize(const Array<ScopedHandleBase<H> >& input) {
+    return sizeof(Array_Data<H>) + Align(input.size() * sizeof(H));
+  }
+  static void SerializeElements(
+      Array<ScopedHandleBase<H> > input,
+      Buffer* buf,
+      Array_Data<H>* output) {
+    for (size_t i = 0; i < input.size(); ++i)
+      output->at(i) = input[i].release();  // Transfer ownership of the handle.
+  }
+  static void DeserializeElements(
+      Array_Data<H>* input, Array<ScopedHandleBase<H> >* output) {
+    Array<ScopedHandleBase<H> > result(input->size());
+    for (size_t i = 0; i < input->size(); ++i)
+      result.at(i) = MakeScopedHandle(FetchAndReset(&input->at(i)));
+    output->Swap(&result);
+  }
+};
+
+template <typename S> struct ArraySerializer<S, typename S::Data_*, true> {
+  static size_t GetSerializedSize(const Array<S>& input) {
+    size_t size = sizeof(Array_Data<typename S::Data_*>) +
+        input.size() * sizeof(internal::StructPointer<typename S::Data_>);
+    for (size_t i = 0; i < input.size(); ++i)
+      size += GetSerializedSize_(input[i]);
+    return size;
+  }
+  static void SerializeElements(
+      Array<S> input,
+      Buffer* buf,
+      Array_Data<typename S::Data_*>* output) {
+    for (size_t i = 0; i < input.size(); ++i) {
+      typename S::Data_* element;
+      Serialize_(input[i].Pass(), buf, &element);
+      output->at(i) = element;
+    }
+  }
+  static void DeserializeElements(
+      Array_Data<typename S::Data_*>* input, Array<S>* output) {
+    Array<S> result(input->size());
+    for (size_t i = 0; i < input->size(); ++i) {
+      S element;
+      Deserialize_(input->at(i), &element);
+      result[i] = element.Pass();
+    }
+    output->Swap(&result);
+  }
+};
+
+template <> struct ArraySerializer<String, String_Data*, false> {
+  static size_t GetSerializedSize(const Array<String>& input) {
+    size_t size = sizeof(Array_Data<String_Data*>) +
+        input.size() * sizeof(internal::StringPointer);
+    for (size_t i = 0; i < input.size(); ++i)
+      size += GetSerializedSize_(input[i]);
+    return size;
+  }
+  static void SerializeElements(
+      Array<String> input,
+      Buffer* buf,
+      Array_Data<String_Data*>* output) {
+    for (size_t i = 0; i < input.size(); ++i) {
+      String_Data* element;
+      Serialize_(input[i], buf, &element);
+      output->at(i) = element;
+    }
+  }
+  static void DeserializeElements(
+      Array_Data<String_Data*>* input, Array<String>* output) {
+    Array<String> result(input->size());
+    for (size_t i = 0; i < input->size(); ++i) {
+      String element;
+      Deserialize_(input->at(i), &element);

[yzshen1, 2014/05/27 22:16:59]

nit: I think we could directly pass in &result[i].

+      result[i].Swap(&element);
+    }
+    output->Swap(&result);
+  }
+};
+
+}  // namespace internal
+
+template <typename E>
+inline size_t GetSerializedSize_(const Array<E>& input) {
+  typedef typename internal::WrapperTraits<E>::DataType F;
+  return internal::ArraySerializer<E, F>::GetSerializedSize(input);
+}
+
+template <typename E, typename F>
+inline void Serialize_(Array<E> input, internal::Buffer* buf,
+                       internal::Array_Data<F>** output) {
+  internal::Array_Data<F>* result =
+      internal::Array_Data<F>::New(input.size(), buf);
+  internal::ArraySerializer<E, F>::SerializeElements(
+      internal::Forward(input), buf, result);
+  *output = result;
+}
+
+template <typename E, typename F>
+inline void Deserialize_(internal::Array_Data<F>* input,
+                         Array<E>* output) {

[yzshen1, 2014/05/27 22:16:59]

Maybe we could consider checking whether |input| is NULL in this function.

I can see that in some places we check NULL pointer before passing it into
Deserialize_(), however, we don't do that in some other places such as
DeserializeElements() above. Maybe we should make it consistent and move the
NULL check into Deserialize_() (for array/struct/string).

(And we could do similar thing for Serialize_(). Currently we don't consistently
check is_null() before calling Serialize_() either.)

+  internal::ArraySerializer<E, F>::DeserializeElements(input, output);
+}
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_ARRAY_SERIALIZATION_H_