Plugin Model and SDK

A "Schema Parser Plugin" is a plugin that allow us to parse messages that have a schema, such as

• ROS1 and ROS2 messages
• Protobuf

Or schemaless messages such as JSON, BSON ,etc.

The parsing step consists in taking the message and "decompose it into a vector of "key/value" pairs.

Example

Consider the ROS message geometry_msgs/Pose. We have the following schema:

'''' MSG: geometry_msgs/Pose

geometry_msgs/Point position geometry_msgs/Quaternion orientation

################## MSG: geometry_msgs/Point float64 x float64 y float64 z

##################

MSG: geometry_msgs/Quaternion float64 x float64 y float64 z float64 w ''''

The input of the parser will be the serialized message, that in this case will be exactly (7*8 = 56 bytes).

The output of the parser will be a vector of 7 key/value pairs, where:

• the key is an index (int32_t). This index will point to a table of strings.
• the value is a VarNumber, i.e. a data structure that can contain any arithmetic type (integer, boolean, floating point).

Specifically, this will be the table of strings that the key will point to:

1. "position/x"
2. "position/y"
3. "position/z"
4. "orientation/x"
5. "orientation/y"
6. "orientation/z"
7. "orientation/w"