mojo/public/tools/bindings/generators/cpp_templates/union_declaration.tmpl

{%- set class_name = union.name ~ "_Data" -%}
{%- set enum_name = union.name ~ "_Tag" -%}
{%- set union_name = union.name ~ "_Union" -%}

class {{class_name}} {
 public:
  static {{class_name}}* New(mojo::internal::Buffer* buf);

  static bool Validate(const void* data,
                       mojo::internal::BoundsChecker* bounds_checker);

  enum class {{enum_name}} : uint64_t {
{%  for field in union.fields %}
    {{field.name|upper}},
{%- endfor %}
  };

  union MOJO_ALIGNAS(8) {{union_name}} {
{%  for field in union.fields %}
    {{field.kind|cpp_field_type}} {{field.name}};
{%- endfor %}
  };

  {{enum_name}} tag;
  {{union_name}} data;

  void EncodePointersAndHandles(std::vector<mojo::Handle>* handles);
  void DecodePointersAndHandles(std::vector<mojo::Handle>* handles);
 
 private:
  {{class_name}}();
  ~{{class_name}}() = delete;
};
static_assert(sizeof({{class_name}}) == 16,
              "Bad sizeof({{class_name}})");