Implement unions as members of structs.

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

 {#  TODO(yzshen): Consider merging the template code for user-defined and
     parameter data structs. That way we can eliminate validate(), fields(),
     encodes() and decodes(). #}
 
 {#  Validates the specified struct field, which is supposed to be an object
     (struct/array/string/map/union).
     This macro is expanded by the validate() macro. #}
 {%- macro _validate_object(struct, packed_field) %}
 {%-   set name = packed_field.field.name %}
 {%-   set kind = packed_field.field.kind %}
 {%-   set wrapper_type = kind|cpp_wrapper_type %}
 {%-   if not kind|is_nullable_kind %}
+{%-     if kind|is_union_kind %}
+  if (object->{{name}}.is_null()) {
+{%-     else %}
   if (!object->{{name}}.offset) {
+{%-     endif %}
     ReportValidationError(
         mojo::internal::VALIDATION_ERROR_UNEXPECTED_NULL_POINTER,
         "null {{name}} field in {{struct.name}} struct");
     return false;
   }
 {%-   endif %}
+{%-   if not kind|is_union_kind %}
   if (!mojo::internal::ValidateEncodedPointer(&object->{{name}}.offset)) {
     ReportValidationError(mojo::internal::VALIDATION_ERROR_ILLEGAL_POINTER);
     return false;
   }
+{%-   endif %}
 {%-   if kind|is_array_kind or kind|is_string_kind %}
   if (!{{wrapper_type}}::Data_::Validate<
           {{kind|get_array_validate_params|indent(10)}}>(
               mojo::internal::DecodePointerRaw(&object->{{name}}.offset),
               bounds_checker)) {
 {%-   elif kind|is_map_kind %}
   if (!{{wrapper_type}}::Data_::Validate<
           {{kind.value_kind|get_map_validate_params|indent(10)}}>(
               mojo::internal::DecodePointerRaw(&object->{{name}}.offset),
               bounds_checker)) {
 {%-   elif kind|is_struct_kind %}
   if (!{{kind|get_name_for_kind}}::Data_::Validate(
           mojo::internal::DecodePointerRaw(&object->{{name}}.offset),
           bounds_checker)) {
+{%-   elif kind|is_union_kind %}
+  // We already claimed the union's memory as part of the struct, so we don't
+  // try to claim the union's memory when validating the union.
+  if (!{{kind.name}}::Data_::Validate(&object->{{name}}, bounds_checker, true)) {
 {%-   else %}
   if (!{{wrapper_type}}::Data_::Validate(
           mojo::internal::DecodePointerRaw(&object->{{name}}.offset),
           bounds_checker)) {
 {%-   endif %}
     return false;
   }
 {%- endmacro %}
 
 {# Validates the specified struct field, which is supposed to be a handle.
@@ skipping 112 matching lines @@
   uint8_t padfinal_[{{pad}}];
 {%-     endif %}
 {%-   endif %}
 {%- endmacro %}
 
 {#  Encodes the specified struct.
     Expands as the body of {{struct.name}}_Data::EncodePointersAndHandles(). #}
 {%- macro encodes(struct) -%}
   MOJO_CHECK(header_.version == {{struct.versions[-1].version}});
 {%-   for pf in struct.packed.packed_fields_in_ordinal_order %}
-{%-     if pf.field.kind|is_object_kind %}
+{%-     if pf.field.kind|is_union_kind %}

[yzshen1, 2015/02/25 21:07:00]

Could you please move the "is_union_kind" part into the "is_object_kind" part?

[azani, 2015/03/03 00:44:16]

Done.

+// TODO(azani): Encode pointers and handles.
+{%-     elif pf.field.kind|is_object_kind %}
   mojo::internal::Encode(&{{pf.field.name}}, handles);
 {%-     elif pf.field.kind|is_any_handle_kind %}
   mojo::internal::EncodeHandle(&{{pf.field.name}}, handles);
 {%-     endif %}
 {%-   endfor %}
 {%- endmacro -%}
 
 {#  Decodes the specified struct.
     This macro is expanded as the body of
     {{struct.name}}_Data:DecodePointersAndHandles(). #}
 {%- macro decodes(struct) -%}
   // NOTE: The memory backing |this| may has be smaller than |sizeof(*this)|, if
   // the message comes from an older version.
 {#-   Before decoding fields introduced at a certain version, we need to add
       a version check, which makes sure we skip further decoding if |this|
       is from an earlier version. |last_checked_version| records the last
       version that we have added such version check. #}
 {%-   set last_checked_version = 0 %}
 {%-   for pf in struct.packed.packed_fields_in_ordinal_order %}
 {%-     set name = pf.field.name %}
 {%-     set kind = pf.field.kind %}
 {%-     if kind|is_object_kind or kind|is_any_handle_kind %}
 {%-       if pf.min_version > last_checked_version %}
 {%-         set last_checked_version = pf.min_version %}
   if (header_.version < {{pf.min_version}})
     return;
 {%-       endif %}
-{%-       if kind|is_object_kind %}
+{%-       if kind|is_union_kind %}

[yzshen1, 2015/02/25 21:07:00]

ditto

[azani, 2015/03/03 00:44:16]

Done.

+// TODO(azani): Decode pointers and handles.
+{%-       elif kind|is_object_kind %}
   mojo::internal::Decode(&{{name}}, handles);
 {%-       else %}
   mojo::internal::DecodeHandle(&{{name}}, handles);
 {%-       endif %}
 {%-     endif %}
 {%-   endfor %}
 {%- endmacro -%}
 
 {#  Computes the serialized size for the specified struct.
     |struct| is the struct definition.
@@ skipping 27 matching lines @@
       wrapper class.
     - method parameters/response parameters: the input is a list of
       arguments. #}
 {%- macro serialize(struct, struct_display_name, input_field_pattern, output, buffer) -%}
   internal::{{struct.name}}_Data* {{output}} =
       internal::{{struct.name}}_Data::New({{buffer}});
 {%- for pf in struct.packed.packed_fields_in_ordinal_order %}
 {%-   set input_field = input_field_pattern|format(pf.field.name) %}
 {%-   set name = pf.field.name %}
 {%-   set kind = pf.field.kind %}
-{%-   if kind|is_object_kind %}
+{%-   if kind|is_union_kind %}

[yzshen1, 2015/02/25 21:07:00]

ditto.

[azani, 2015/03/03 00:44:15]

Done.

+  internal::{{pf.field.kind.name}}_Data* {{pf.field.name}}_ptr = &result->{{pf.field.name}};

[yzshen1, 2015/02/25 21:07:00]

Please use {{input_field}}, {{buffer}} and {{output}} instead of "input->xxx",
"buf" and "result".

Besides, {{name}} and {{kind}} instead of {{pf.field.name}} and
{{pf.field.kind}}.

[azani, 2015/03/03 00:44:15]

Done.

+  Serialize_(mojo::internal::Forward(input->{{pf.field.name}}), buf, &{{pf.field.name}}_ptr);
+{%-   elif kind|is_object_kind %}
 {%-     if kind|is_array_kind %}
   mojo::SerializeArray_<{{kind|get_array_validate_params|indent(24)}}>(
       mojo::internal::Forward({{input_field}}), {{buffer}}, &{{output}}->{{name}}.ptr);
 {%-     elif kind|is_map_kind %}
   mojo::SerializeMap_<{{kind.value_kind|get_map_validate_params|indent(24)}}>(
       mojo::internal::Forward({{input_field}}), {{buffer}}, &{{output}}->{{name}}.ptr);
 {%-     else %}
   Serialize_(mojo::internal::Forward({{input_field}}), {{buffer}}, &{{output}}->{{name}}.ptr);
 {%-     endif %}
 {%-     if not kind|is_nullable_kind %}
@@ skipping 42 matching lines @@
 {%-   set last_checked_version = 0 %}
 {%-   for pf in struct.packed.packed_fields_in_ordinal_order %}
 {%-     set output_field = output_field_pattern|format(pf.field.name) %}
 {%-     set name = pf.field.name %}
 {%-     set kind = pf.field.kind %}
 {%-     if pf.min_version > last_checked_version %}
 {%-       set last_checked_version = pf.min_version %}
     if ({{input}}->header_.version < {{pf.min_version}})
       break;
 {%-     endif %}
-{%-     if kind|is_object_kind %}
+{%-     if kind|is_union_kind %}

[yzshen1, 2015/02/25 21:07:00]

Please move this if into the if for "is_object_kind".

[azani, 2015/03/03 00:44:16]

Done.

+    Deserialize_(&input->{{pf.field.name}}, &result->{{pf.field.name}});

[yzshen1, 2015/02/25 21:07:00]

Please use {{output_field}}, {{input}}.

Besides, {{name}} instead of {{pf.field.name}}

[azani, 2015/03/03 00:44:16]

Done.

+{%-     elif kind|is_object_kind %}
     Deserialize_({{input}}->{{name}}.ptr, &{{output_field}});
 {%-     elif kind|is_interface_kind or kind|is_interface_request_kind %}
     {{output_field}}.Bind(mojo::MakeScopedHandle(mojo::internal::FetchAndReset(&{{input}}->{{name}})));
 {%-     elif kind|is_any_handle_kind %}
     {{output_field}}.reset(mojo::internal::FetchAndReset(&{{input}}->{{name}}));
 {%-     elif kind|is_enum_kind %}
     {{output_field}} = static_cast<{{kind|cpp_wrapper_type}}>({{input}}->{{name}});
 {%-     else %}
     {{output_field}} = {{input}}->{{name}};
 {%-     endif %}
 {%-   endfor %}
   } while (false);
 {%- endmacro %}