5. DDS Options for Protocol Buffers

5.1. Message Options

Table 5.1 Message Options (.omg.dds.type)

Option	Description	Value	IDL4 Output
.name	Specifies a custom name that will be used to identify the type when used on a DDS topic.	"MyCustomName" (non-empty string literal)	@type_name("MyCustomName")
.extensibility	Controls the extensibility annotation of the corresponding IDL4 struct.	MUTABLE	@mutable
		FINAL	@final
		APPENDABLE	@appendable
.default_id	Specifies the default policy used to control the default @id annotation emitted for each member of an IDL4 struct.	PROTOBUF_DEFAULT_ID	@id(N) (on members)
		DDS_DEFAULT_ID	N/A (use default DDS id for each member)
.auto_id	Controls the @autoid annotation for the IDL4 struct.	NO_AUTO_ID	N/A (no annotation)
		SEQUENTIAL	@autoid(sequential)
		HASH	@autoid(hash)

5.2. Field Options

Table 5.2 Field Options (.omg.dds.member)

Option	Description	Value	IDL4 Output
.key	Specifies whether the corresponding member is part of the DDS key.	true	@key
		false (default)	N/A (no annotation)
.optional	Controls whether the corresponding member should be annotated as @optional. If specified, this option will take precedence over the default annotionation derived from the field’s “presence”.	true	@optional
		false	N/A (no annotation)
.default_id	Controls the default @id annotation emitted for the corresponding member. If specified, this option will take precedence over the default policy set at the message level via option .omg.dds.type.default_id.	See .omg.dds.type.default_id.
.id	Explicitly set and emit a specific @id annotation for the corresponding member.	N (32-bit unsigned integer)	@id(N)
.hash_id	Generates the @hashid annotation for the corresponding member with the specified source string.	"My String" (non-empty string literal)	@hashid("My String")

5.3. omg/dds/descriptor.proto

Listing 5.1 omg/dds/descriptor.proto

syntax = "proto2";
import "google/protobuf/descriptor.proto";

package omg.dds;

enum ExtensibilityKind {
  MUTABLE = 0; // "Mutable" extensibility, members can be reordered,  added, or removed.
  APPENDABLE = 1; // "Appendable" extensibility, members can be added or removed from the end.
  FINAL = 2; // "Final" extensibility, member cannot be added, removed or reordered.
}

enum DefaultIdKind {
  PROTOBUF_DEFAULT_ID = 0; // Derive an @id annotation for each DDS member from the corresponding protobuf field number.
  DDS_DEFAULT_ID = 1; // Do not emit @id annotations, unless explicitly provided through the "omg.dds.member.id" option.
}

enum AutoIdKind {
  NO_AUTO_ID = 0; // Do not emit an @autoid annotation
  SEQUENTIAL = 1; // Emit @autoid(sequential) to use sequential IDs starting from 0
  HASH = 2; // Emit @autoid(hash), to use a hash of the field name to generate IDs
}

message TypeAnnotation {
  optional string name = 1;
  optional ExtensibilityKind extensibility = 2;
  optional DefaultIdKind default_id = 3;
  optional AutoIdKind auto_id = 4;
}

extend google.protobuf.MessageOptions {
  optional TypeAnnotation type = 7400;
}

message MemberAnnotation {
  optional bool key = 1;
  optional bool filterable = 2;
  optional bool optional = 3;
  optional DefaultIdKind default_id = 4;
  optional uint32 id = 5;
  optional string hash_id = 6;
}

extend google.protobuf.FieldOptions {
  optional MemberAnnotation member = 7400;
}