Mojo C++ bindings: add StringTraits and ArrayTraits for STL types.

mojo/public/cpp/bindings/array_traits_stl.h

+// 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.
+
+#ifndef MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_STL_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_STL_H_
+
+#include <vector>
+
+#include "mojo/public/cpp/bindings/array_traits.h"
+
+namespace mojo {
+
+template <typename T>
+struct ArrayTraits<std::vector<T>> {
+  using Element = T;
+
+  static bool IsNull(const std::vector<T>& input) {
+    // std::vector<> is always converted to non-null mojom array.
+    return false;
+  }
+
+  static void SetToNull(std::vector<T>* output) {
+    // std::vector<> doesn't support null state. Set it to empty instead.
+    output->clear();
+  }
+
+  static size_t GetSize(const std::vector<T>& input) { return input.size(); }
+
+  static T* GetData(std::vector<T>& input) { return input.data(); }
+
+  static const T* GetData(const std::vector<T>& input) { return input.data(); }
+
+  static typename std::vector<T>::reference GetAt(std::vector<T>& input,
+                                                  size_t index) {
+    return input[index];
+  }
+
+  static typename std::vector<T>::const_reference GetAt(
+      const std::vector<T>& input,
+      size_t index) {
+    return input[index];
+  }
+
+  static void Resize(std::vector<T>& input, size_t size) { input.resize(size); }
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_STL_H_