Value Types

Overview

Robot Raconteur passes “Value Types” between clients and services by value. The values are “serialized” to a binary format that can be transmitted over a network. The values are then “deserialized” back into the original data type. The serialization and deserialization process is handled transparently by the Robot Raconteur library. Because Robot Raconteur supports multiple programming languages, the value types are defined using Robot Raconteur “Service Definitions,” which provide a common language-independent format for defining data types. The Value Types are carefully designed to support robotics and automation applications.

See also the Robot Raconteur Framework Service Definition Documentation

The following data types are supported by Robot Raconteur:

  • bool - A boolean value that can be either true or false. * Arrays and multidimensional arrays of booleans.

  • Numeric types including uint8, int8, uint16, int16, uint32, int32, uint64, int64, single, double, csingle, and cdouble. * Arrays and multidimensional arrays of numeric types.

  • string - A string of characters.

  • struct - A structure that contains a collection of fields.

  • pod - A “Plain Old Data” structure that contains a collection of fields that are stored in contiguous memory. * Arrays and multidimensional arrays of POD types.

  • namedarray - A structure that contains a collection of fields that are stored as a union between a structure and a numeric array in contiguous memory. * Arrays and multidimensional arrays of namedarray types.

  • Collection types including list, map{int32}, and map{string}. * Any of the above types can be used as the value type in a collection type.

The struct, pod, and namedarray types are defined using the Robot Raconteur “Service Definitions” format.

Object “members” are used to interact with services and pass data between clients and services. The examples on this page use property types to pass data between clients and services. The value types can all be used with all member types.

The example service definition experimental.value_types is used for the examples on this page. The service definition is shown below:


Numeric Types

Robot Raconteur supports numeric types including uint8, int8, uint16, int16, uint32, int32, uint64, int64, single, double, csingle, and cdouble. For the purpose of this section, bool is also considered a numeric type. Scalar numbers are converted to the built-in numeric types in the client programming language. Numeric types can also be stored in arrays and multidimensional arrays.

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for numeric types:

The examples below show how to use the numeric types in Python, MATLAB, LabView, C#, and C++.

String Type

Robot Raconteur uses the built-in string types in the client programming language. Note that strings cannot be stored in arrays since internally strings are already stored as arrays of characters.

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for numeric types:

The examples below show how to use strings in Python, MATLAB, LabView, C#, and C++.

Structure Types

Structures are a collection of fields that can contain any value type, including itself. Structures are defined using the Robot Raconteur “Service Definitions” format. Structures are nullable. The following examples demonstrate using the experimental.value_types.MyStructure structure type:

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for structure types:

The examples below show how to use structures in Python, MATLAB, LabView, C#, and C++.

Pod Types

Pods are a collections of fields that have a fixed memory layout. Pods have a restricted set of allowed field types including numbers, arrays, namedarrays, and other pods. See the Robot Raconteur Framework Service Definition Documentation for more information about the allowed contents of pods. Unlike structures, pods store all their data within the pod itself in contiguous memory, and do not contain pointers to other data. They are guaranteed to have a maximum binary size. The following examples demonstrate using the experimental.value_types.MyPod pod type:

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for pod types:

The examples below show how to use pods in Python, MATLAB, LabView, C#, and C++.

NamedArray Types

Namedarrays represent a union type between a structure and a numeric array. A vector is an example of a type that can be represented either as a structure with three fields, or as a numeric array with three elements. Namedarrays are very efficient compared to the other data types since they can be transmitted or manipulated as a plain array. All fields in the namedarray must have the same numeric type. Other namedarrays and arrays may also be used as fields, but they must have the same underlying numeric type and a fixed size. The following examples demonstrate using the experimental.value_types.MyVector3, experimental.value_types.MyQuaternion, and experimental.value_types.MyPose namedarray types:

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for namedarray types:

The examples below show how to use namedarrays in Python, MATLAB, LabView, C#, and C++.

Container Types

Robot Raconteur containers store a collection of values using lists and maps. The available container types are list, map{int32}, and map{string}. The container types can store any value type, except for other containers. Containers are nullable.

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for container types:

The examples below show how to use containers in Python, MATLAB, LabView, C#, and C++.

varvalue Type

Varvalue is a special type that can store any value type, and is a form of variant. See the language documentation for more details on how the variant is implemented in each language. The varvalue type is nullable.

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for varvalue types:

The examples below show how to use varvalue in Python, MATLAB, LabView, C#, and C++.

Nullable Types

Structures, containers, and varvalues are nullable, meaning they can be set to null. All other value types are not nullable.

The following members from the experimental.value_types.ValueTypesExample object are used in the examples for nullable types:

The examples below show how to use nullable types in Python, MATLAB, LabView, C#, and C++.