Mojo C++ bindings: provide data view for all object types.

mojo/public/cpp/bindings/map_data_view.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_MAP_DATA_VIEW_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_MAP_DATA_VIEW_H_
+
+#include "base/logging.h"
+#include "mojo/public/cpp/bindings/array.h"
+#include "mojo/public/cpp/bindings/array_data_view.h"
+#include "mojo/public/cpp/bindings/lib/bindings_internal.h"
+#include "mojo/public/cpp/bindings/lib/serialization_context.h"
+#include "mojo/public/cpp/bindings/lib/serialization_forward.h"
+#include "mojo/public/cpp/bindings/map.h"
+
+namespace mojo {
+
+template <typename K, typename V>
+class MapDataView {
+ public:
+  using Data_ = typename internal::MojomTypeTraits<
+      Map<typename internal::DataViewTraits<K>::MojomType,
+          typename internal::DataViewTraits<V>::MojomType>>::Data;
+
+  MapDataView() {}
+
+  MapDataView(Data_* data, internal::SerializationContext* context)
+      : keys_(data ? data->keys.Get() : nullptr, context),
+        values_(data ? data->values.Get() : nullptr, context) {}
+
+  bool is_null() const {
+    DCHECK_EQ(keys_.is_null(), values_.is_null());
+    return keys_.is_null();
+  }
+
+  size_t size() const {
+    DCHECK_EQ(keys_.size(), values_.size());
+    return keys_.size();
+  }
+
+  ArrayDataView<K>& keys() { return keys_; }
+  const ArrayDataView<K>& keys() const { return keys_; }
+
+  template <typename U>
+  bool ReadKeys(U* output) {
+    return internal::Deserialize<
+        Array<typename internal::DataViewTraits<K>::MojomType>>(
+        keys_.data_, output, keys_.context_);
+  }
+
+  ArrayDataView<V>& values() { return values_; }
+  const ArrayDataView<V>& values() const { return values_; }
+
+  template <typename U>
+  bool ReadValues(U* output) {
+    return internal::Deserialize<
+        Array<typename internal::DataViewTraits<V>::MojomType>>(
+        values_.data_, output, values_.context_);
+  }
+
+ private:
+  ArrayDataView<K> keys_;
+  ArrayDataView<V> values_;
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_MAP_DATA_VIEW_H_