Mojo C++ bindings: make String16 and gfx::Size available in Blink

third_party/WebKit/Source/platform/mojo/CommonCustomTypesStructTraits.cpp

+// 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 "platform/mojo/CommonCustomTypesStructTraits.h"
+
+#include "mojo/public/cpp/bindings/array_traits_wtf_vector.h"
+#include <cstring>
+
+namespace mojo {
+
+// static
+mojo::ConstCArray<uint16_t>
+StructTraits<mojo::common::mojom::String16DataView, ::WTF::String>::data(
+    const ::WTF::String& str) {
+  DCHECK(!str.isNull())
+      << "mojo::common::mojom::String16 only accepts non-null blink::WebString";
+  DCHECK(!str.is8Bit());

[esprehn, 2016/10/05 17:38:52]

What makes sure the string is 16bit here? I think you need to convert here,
ideally mojo would support writing directly into the output buffer without the
extra malloc and upconvert, but hopefully this is rare

[Ken Rockot(use gerrit already), 2016/10/05 17:47:55]

What do you mean by writing directly into the output buffer? The wire format of
this type is fixed. It's a 16-bit string on the wire, always.

+
+  return mojo::ConstCArray<uint16_t>(
+      str.length(), reinterpret_cast<const uint16_t*>(str.characters16()));
+}
+
+// static
+bool StructTraits<mojo::common::mojom::String16DataView, ::WTF::String>::Read(
+    mojo::common::mojom::String16DataView data,
+    ::WTF::String* out) {
+  mojo::ArrayDataView<uint16_t> view;
+  data.GetDataDataView(&view);
+  if (view.is_null())
+    return false;
+  *out =
+      ::WTF::String(reinterpret_cast<const UChar*>(view.data()), view.size());
+  // WTF::String is constructed as 8-bit if the string is empty.
+  out->ensure16Bit();
+  return true;
+}
+
+}  // namespace mojo