Add ArrayTraits<CArray<T>> utility template

mojo/public/cpp/bindings/array_traits_carray.h

Index: mojo/public/cpp/bindings/array_traits_carray.h
diff --git a/mojo/public/cpp/bindings/array_traits_carray.h b/mojo/public/cpp/bindings/array_traits_carray.h
new file mode 100644
index 0000000000000000000000000000000000000000..9efa88bb648e7170e06610af5ccaf271b37081ca
--- /dev/null
+++ b/mojo/public/cpp/bindings/array_traits_carray.h
@@ -0,0 +1,53 @@
+// 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_CARRAY_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_CARRAY_H_
+
+#include <vector>

[yzshen1, 2016/06/07 22:29:29]

No need to have this include.

[Fady Samuel, 2016/06/08 00:50:06]

Done.

+
+#include "mojo/public/cpp/bindings/array_traits.h"
+
+namespace mojo {
+
+template <typename T>
+struct CArray {
+  CArray() : size(0), max_size(0), data(nullptr) {}
+  explicit CArray(size_t max_size)
+      : size(0), max_size(max_size), data(nullptr) {}
+  CArray(size_t size, size_t max_size, T* data)
+      : size(size), max_size(max_size), data(data) {}
+  size_t size;
+  size_t max_size;

[yzshen1, 2016/06/07 22:29:29]

Does it make sense to:
- either making this const
- or removing it and making |size| an in/out kind of member?

[Fady Samuel, 2016/06/08 00:50:06]

Made it const. I'd prefer not to have it in and out because I worry that it's
confusing and if Resize is called more than once, might fail.

+  T* data;
+};
+
+template <typename T>
+struct ArrayTraits<CArray<T>> {
+  using Element = T;
+
+  static size_t GetSize(const CArray<T>& input) { return input.size; }
+
+  static T* GetData(CArray<T>& input) { return input.data; }
+
+  static const T* GetData(const CArray<T>& input) { return input.data; }
+
+  static T& GetAt(CArray<T>& input, size_t index) { return input.data[index]; }
+
+  static const T& GetAt(const CArray<T>& input, size_t index) {
+    return input.data[index];
+  }
+
+  static bool Resize(CArray<T>& input, size_t size) {
+    if (size > input.max_size)
+      return false;
+
+    input.size = size;
+    return true;
+  }
+};
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_CARRAY_H_