Mojo bindings: Add string support to StructTraits

This CL enables string-typed fields in structs to be
serialized and deserialized via StructTraits using
base::StringPiece as an intermediate interface between
the native type and the message buffer.

BUG=577686
R=yzshen@chromium.org

Review URL: https://codereview.chromium.org/1719183002

Cr-Commit-Position: refs/heads/master@{#376952}

3 files changed, 70 insertions, 7 deletions

diff --git a/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
index 2691e772..fa7dd15 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/module.h.tmpl
@@ -18,6 +18,7 @@
 #include <stdint.h>
 #include <ostream>
 
+#include "base/strings/string_piece.h"
 #include "mojo/public/cpp/bindings/array.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr.h"
 #include "mojo/public/cpp/bindings/associated_interface_ptr_info.h"
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_declaration.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_declaration.tmpl
index a2cee64..d0ef30a4 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_declaration.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_declaration.tmpl
@@ -53,8 +53,13 @@ class {{struct.name}}_Reader {
 {%-   for pf in struct.packed.packed_fields_in_ordinal_order %}
 {%-     set kind = pf.field.kind -%}
 {%-     set name = pf.field.name -%}
+{%-     if kind|is_nullable_kind %}
+  bool has_{{name}}() const;
+{%-     endif %}
 {%-     if kind|is_struct_kind and not kind|is_native_only_kind %}
   {{kind|get_name_for_kind}}::Reader {{name}}() const;
+{%-     elif kind|is_string_kind %}
+  base::StringPiece {{name}}() const;
 {%-     elif kind|is_union_kind %}
   // TODO(rockot): Support reading unions. ({{name}}() omitted)
 {%-     elif kind|is_object_kind %}
@@ -86,10 +91,21 @@ struct {{struct.name}}_SerializerTraits_ {
   static size_t GetSize(const NativeType& input) {
     size_t size = sizeof(internal::{{struct.name}}_Data);
 {%- for pf in struct.packed.packed_fields_in_ordinal_order %}
-{%-   if pf.field.kind|is_object_kind %}
-    NOTREACHED() << "Mojom struct traits only support POD fields at this time. "
-        << "Cannot determine the size of field {{pf.field.name}}";
+    do {
+{%-   if pf.field.kind|is_nullable_kind %}
+      if (!mojo::StructTraits<{{struct.name}}, NativeType>
+              ::has_{{pf.field.name}}(input))
+        break;
+{%-   endif %}
+{%-   if pf.field.kind|is_string_kind %}
+      size += mojo::internal::String_Data::Traits::GetStorageSize(
+          static_cast<uint32_t>(mojo::StructTraits<{{struct.name}}, NativeType>
+              ::{{pf.field.name}}(input).size()));
+{%-   elif pf.field.kind|is_object_kind %}
+      NOTREACHED() << "Unsupported field type for StructTraits: "
+                   << "{{pf.field.name}}";
 {%-   endif %}
+    } while (false);
 {%- endfor %}
     return size;
   }
@@ -99,11 +115,30 @@ struct {{struct.name}}_SerializerTraits_ {
                         internal::{{struct.name}}_Data** output) {
     internal::{{struct.name}}_Data* result =
         internal::{{struct.name}}_Data::New(buffer);
-{%- for pf in struct.packed.packed_fields_in_ordinal_order %}
+{%- for pf in struct.packed.packed_fields_in_ordinal_order -%}
 {%-   set name = pf.field.name -%}
 {%-   set kind = pf.field.kind %}
-    result->{{name}} = mojo::StructTraits<{{struct.name}}, NativeType>
-        ::{{name}}(input);
+    do {
+{%-   if kind|is_nullable_kind %}
+      if (!mojo::StructTraits<{{struct.name}}, NativeType>
+              ::has_{{name}}(input))
+        break;
+{%-   endif %}
+{%-   if kind|is_string_kind %}
+      base::StringPiece input_{{name}} =
+          mojo::StructTraits<{{struct.name}}, NativeType>::{{name}}(input);
+      result->{{name}}.ptr =
+          mojo::internal::String_Data::New(input_{{name}}.size(), buffer);
+      memcpy(result->{{name}}.ptr->storage(), input_{{name}}.data(),
+             input_{{name}}.size());
+{%-   elif kind|is_object_kind %}
+      NOTREACHED() << "Unsupported field type for StructTraits: "
+                   << "{{pf.field.name}}";
+{%-   else %}
+      result->{{name}} = mojo::StructTraits<{{struct.name}}, NativeType>
+          ::{{name}}(input);
+{%-   endif %}
+    } while (false);
 {%- endfor %}
     *output = result;
   }
diff --git a/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_definition.tmpl b/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_definition.tmpl
index e6577b9..485a8ec 100644
--- a/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_definition.tmpl
+++ b/mojo/public/tools/bindings/generators/cpp_templates/struct_serialization_definition.tmpl
@@ -39,11 +39,38 @@ bool Deserialize_(internal::{{struct.name}}_Data* input,
 
 {%- for pf in struct.packed.packed_fields_in_ordinal_order %}
 {%-   set name = pf.field.name -%}
-{%-   set kind = pf.field.kind -%}
+{%-   set kind = pf.field.kind %}
+{%-   if kind|is_nullable_kind %}
+bool {{struct.name}}_Reader::has_{{name}}() const {
+{%-  if kind|is_union_kind %}
+  return !data_->{{name}}.is_null();
+{%-  elif kind|is_object_kind %}
+  return data_->{{name}}.ptr != nullptr;
+{%-  elif kind|is_interface_kind %}
+  return data_->{{name}}.handle.is_valid();
+{%-  elif kind|is_interface_request_kind %}
+  return data_->{{name}}.is_valid();
+{%-  elif kind|is_associated_interface_kind %}
+  return data_->{{name}}.interface_id == mojo::internal::kInvalidInterfaceId;
+{%-  elif kind|is_associated_interface_request_kind %}
+  return data_->{{name}} == mojo::internal::kInvalidInterfaceId;
+{%-  elif kind|is_any_handle_kind %}
+  return data_->{{name}}.is_valid();
+{%-  else %}
+  return !!data_->{{name}};
+{%-   endif %}
+}
+{%-   endif %}
 {%-   if kind|is_struct_kind and not kind|is_native_only_kind %}
 {{kind|get_name_for_kind}}_Reader {{struct.name}}_Reader::{{name}}() const {
   return {{kind|get_name_for_kind}}_Reader(data_->{{name}}.ptr, context_);
 }
+{%-   elif kind|is_string_kind %}
+base::StringPiece {{struct.name}}_Reader::{{name}}() const {
+  DCHECK(data_->{{name}}.ptr);
+  return base::StringPiece(data_->{{name}}.ptr->storage(),
+                           data_->{{name}}.ptr->size());
+}
 {%-   endif %}
 {%- endfor %}