cx_protobuf_plugin

This package offers the `cx::ProtobufPlugin’ plugin that allows to communicate via protobuf through protobuf_comm.

Usage

Register this plugin with the plugin manager. It’s configuration parameters are depicted in this example setup below.

clips_manager:
  ros__parameters:
    environments: ["main"]
    main:
      plugins: ["protobuf"]

    protobuf:
      plugin: "cx::ProtobufPlugin"
      # When specifying relative paths, look at the share directories of the listed packages to resolve them.
      # Attempts to resolve the relative paths in order of the listed packages
      # Defaults to an empty list
      pkg_share_dirs: ["cx_bringup"]
      # Specify directories to look for protobuf messages.
      # Supports absolute paths or relative paths using the share directories specified above.
      # Defaults to an empty list
      proto_paths: ["proto"]

This automatically makes all proto files in the given paths available for serialization and deserialization and is the recommended use for this plugin.

It is also possible to instead register types explicitly by looking them up from a linked library. However, this requires to build a shared library from proto files and then link it together with the cx_protobuf_plugin.

In order to accomplish this, this plugin offers two cmake macros:

# Generates a new plugin called NEW_PLUGIN_NAME (should be a name in CamelCase, e.g., CustomProtobufPlugin) given a list of protobuf message definitions PROTO_FILES.
cx_generate_linked_protobuf_plugin_from_proto(NEW_PLUGIN_NAME PROTO_FILES)
# Generates a new plugin called NEW_PLUGIN_NAME (should be a name in CamelCase, e.g., CustomProtobufPlugin) given a shared library that is linked against via target_link_libraries().
cx_generate_linked_protobuf_plugin_from_lib(NEW_PLUGIN_NAME SHARED_LIBRARY_TARGET)

CLIPS Features

This plugin defines deftemplates, rules and user-defined functions that are described below.

It allows two differnet way of communication. Either via broadcast peers or via client server connection.

Deftemplates

; Asserted by the create-subscription function.
; Retracted by the destroy-subscription function.
(deftemplate protobuf-msg
  (slot type (type STRING))            ; (package + "." +) message-name
  (slot comp-id (type INTEGER))
  (slot msg-type (type INTEGER))
  (slot rcvd-via (type SYMBOL)
    (allowed-values STREAM BROADCAST)
  )
  (multislot rcvd-from                 ; address and port
    (cardinality 2 2)
  )
  (slot rcvd-at (type FLOAT))          ; ros timestamp in seconds
  (slot client-type (type SYMBOL)
    (allowed-values SERVER CLIENT PEER)
  )
  (slot client-id (type INTEGER))
  (slot ptr (type EXTERNAL-ADDRESS))
)

(deftemplate protobuf-receive-failed
  (slot comp-id (type INTEGER))
  (slot msg-type (type INTEGER))
  (slot rcvd-via (type SYMBOL)
    (allowed-values STREAM BROADCAST)
  )
  (multislot rcvd-from (cardinality 2 2))
  (slot client-id (type INTEGER))
  (slot message (type STRING))
)

(deftemplate protobuf-server-receive-failed
  (slot comp-id (type INTEGER))
  (slot msg-type (type INTEGER))
  (slot rcvd-via (type SYMBOL)
    (allowed-values STREAM BROADCAST)
  )
  (multislot rcvd-from (cardinality 2 2))
  (slot client-id (type INTEGER))
  (slot message (type STRING))
)

Defrules

It defines defrules and a defglobal to clean up the fact once the end of the agenda is reached:

```lisp (defglobal ?PRIORITY-PROTOBUF-RETRACT = -10000 )

(defrule protobuf-cleanup-receive-failed (declare (salience ?PRIORITY-PROTOBUF-RETRACT)) ?f <- (protobuf-receive-failed (comp-id ?cid) (msg-type ?mt) (rcvd-from ?host ?port) (message ?msg)) => (retract ?f) (printout t “Protobuf rcv fail for “ ?cid “:” ?mt “ from “ ?host “:” ?port “: “ ?msg crlf)

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