AMiRo-OS

/'

µRtWare is a lightweight publish/subscribe middleware for real-time

applications. It was developed as part of the software habitat for the

Autonomous Mini Robot [1] (AMiRo) but can be used for other purposes as well.

Copyright (C) 2018..2018  Thomas Schöpping et al.

This program is free software: you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation, either version 3 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program.  If not, see <http://www.gnu.org/licenses/>.

'/

@startuml

title **µRtWare**\nOverview\n

package "primitives" {

  /' Temporal delay in microseconds. '/

  class urt_delay_t <<(T,lightblue)>> {

    .. either ..

    uint32_t

    .. or ..

    uint64_t

  }

  /' Well defined error codes. '/

  enum urt_status_t {

    URT_STATUS_OK = 0

    URT_STATUS_WARNING = 1

    URT_STATUS_ERROR = -1

  }

  /' Topic ID type. '/

  class urt_topicid_t <<(T,lightblue)>> {

    'configurable

    uin8_t

    .. or ..

    uint16_t

    .. or ..

    uint32_t

    .. or ..

    uint64_t

  }

  /' Just a function for debugging. '/

  class urt_debug <<(F,white)>> {

      'Checks the condition in debug mode.

    + urtDebugAssert(condition : bool) : void

  }

  /' Node synchronization type. '/

  class urt_nodesync_t <<T,lightblue>> {

    'configurable

    uin8_t

    .. or ..

    int8_t

    .. or ..

    uint16_t

    .. or ..

    int16_t

    .. or ..

    uint32_t

    .. or ..

    int32_t

    .. or ..

    uint64_t

    .. or ..

    int64_t

  }

} /' package "primitives" '/

package "interfaces" {

  /' Not a type but a set of configuration macros. '/

  class urt_config <<(C,grey)>> {

      'Selection to en-/disable debug checks.

    + URT_CONFIG_DEBUG : bool

  }

  /' OS time type with arbitrary resolution. '/

  class urt_osTime_t <<(T,lightblue)>> {

      'Converts an OS time to 64 bit microsecond precise value.

    + urtTime2Us (t : urt_osTime_t*) : uint64_t

      'Retrieves the current time.

    + urtTimeNow (void) : urt_osTime_t

  }

  /' OS mutex lock interface. '/

  class urt_osMutex_t <<(T,lightblue)>> {

      'Initializes a urt_osMutex_t object.

    + urtMutexInit (mutex : urt_osmutex_t*) : void

      'Block the thread until the mutex could be locked.

    + urtMutexLock (mutex : urt_osmutex_t*) : void

      'Tries to lock the mutex, but does not block but immediately returns an indicator.

    + urtMutexTryLock (mutex : urt_osmutex_t*) : bool

      'Unlocks a previously locked mutex.

    + urtMutexUnlock (mutex : urt_osmutex_t*) : void

  }

  package "condition variable" {

    /' Return type for the wait function on condition variables. '/

    enum urt_condvarStatus_t {

        'The condition variable has been signaled.

      + URT_CONDVAR_STATUS_SIGNAL = 0

        'The condition variable has been broadcasted.

      + URT_CONDVAR_STATUS_BROADCAST = 1

        'The wait function timed out.

      + URT_CONDVAR_STATUS_TIMEOUT = 2

    }

    /' Condition variable interface. '/

    class urt_osCondvar_t <<(T,lightblue)>> {

        'Initializes a urt_osCondvar_t object.

      + urtCondvarInit (condvar : urt_osCondvar_t*) : void

        'Signals one thread that is waiting for the condition variable.

      + urtConvarSignal (condvar : urt_osCondvar_t*) : void

        'Signals all threads that are waiting for the condition variable.

      + urtCondvarBroadcast (condvar : urt_osCondvar_t*) : void

        'Waits for the condition variable.

      + urtCondvarWait (condvar : urt_osCondvar_t*, mutex : urt_osMutex_t*, timeout : urt_delay_t) : urt_condvarStatus_t

    }

    urt_osCondvar_t ..> urt_osMutex_t

    urt_osCondvar_t ..> urt_delay_t

    urt_osCondvar_t ..> urt_condvarStatus_t

  } /' package "condition variable" '/

  package "timer" {

    /' Timer callback definition. '/

    class urt_osTimerCallback_t <<(T,lightblue)>> {

      urt_osTimerCallback_t (parameter : void*) : void

    }

    /' OS timer interface. '/

    class urt_osTimer_t <<(T,lightblue)>> {

        'Initializes an urt_osTimer_t object.

      + urtTimerInit (timer : urt_osTimer_t*) : void

        'Sets the timer to a specified delay with specified callback and arguments.

      + urtTimerSet (timer : urt_osTimer_t*, delay : urt_delay_t, callback : urt_osTimerCallback_t*, parameter : void*) : urt_status_t

        'Resets the timer.

      + urtTimerReset (timer : urt_osTimer_t*) : urt_status_t

        'Check whether the timer is already armed.

      + urtTimerIsArmed (timer : urt_timer_t*) : bool

    }

    urt_osTimer_t ..> urt_delay_t

    urt_osTimer_t ..> urt_status_t

    urt_osTimer_t ..> urt_osTimerCallback_t

  } /' package "timer" '/

  package "thread" {

    /' Thread priority type. '/

    class urt_osThreadPrio_t <<(T,lightblue)>>

    /' Thread main function type. '/

    class urt_osThreadFunction_t <<(T,lightblue)>> {

      urt_osThreadFunction_t (arg : void*) : void

    }

    /' Thread terminate signals. '/

    enum urt_osThreadTerminateSignal_t {

      'Signal to request termination asap.

      URT_THREAD_TERMINATE_REQUEST = 15

      'Signal to kill a thread immediately.

      URT_THREAD_TERMINATE_KILL = 9

    }

    /' Thread execution states. '/

    enum urt_osThreadState_t {

      'Thread is currently being executed.

      URT_THREAD_STATE_RUNNING = 0

      'Thread is ready but waiting to be scheduled.

      URT_THREAD_STATE_READY = 1

      'Thread is actively sleeping.

      URT_THREAD_STATE_SLEEPING = 2

      'Thread has ben suspended explicitely.

      URT_THREAD_STATE_SUSPENDED = 3

      'Thread is waiting for something (e.g. Mutex, event, etc.).

      URT_THREAD_STATE_WAITING = 4

      'Thread has terminated.

      URT_THREAD_STATE_TERMINATED = 5

    }

    /' OS thread interface. '/

    class urt_osThread_t <<(T,lightblue)>> {

        'Minimum priority for low priority threads.

      + URT_THREAD_PRIO_LOW_MIN : urt_osThreadPrio_t

        'Maximum priority for low priority threads.

      + URT_THREAD_PRIO_LOW_MAX : urt_osThreadPrio_t

        'Minimum priority for normal priority threads.

      + URT_THREAD_PRIO_NORMAL_MIN : urt_osThreadPrio_t

        'Maximum priority for normal priority threads.

      + URT_THREAD_PRIO_NORMAL_MAX : urt_osThreadPrio_t

        'Minimum priority for high priority threads.

      + URT_THREAD_PRIO_HIGH_MIN : urt_osThreadPrio_t

        'Maximum priority for high priority threads.

      + URT_THREAD_PRIO_HIGH_MAX : urt_osThreadPrio_t

        'Minimum priority for real-time threads.

      + URT_THREAD_PRIO_RT_MIN : urt_osThreadPrio_t

        'Maximum priority for real-time threads.

      + URT_THREAD_PRIO_RT_MAX : urt_osThreadPrio_t

      ..

        'Maximum sleep interval in seconds (as float).

      + URT_THREAD_MAX_SLEEP : float

        'Maximum sleep interval in seconds.

      + URT_THREAD_MAX_SSLEP : unsigned int

        'Maximum sleep interval in milliseconds.

      + URT_THREAD_MAX_MSLEEP : unsigned int

        'Maximum sleep interval in microseconds.

      + URT_THREAD_MAX_USLEEP : unsigned int

      __

        'Macro to setup working area as static variable (handles alignment if required).

      + URT_THREAD_WORKING_AREA (varname, stacksize)

      ..

        'Initializes an urt_osThread_t object.

      + urtThreadInit (wa : void*, wasize : size_t, func : urt_osThreadFunction_t*, arg : void*) : urt_osThread_t*

        'Starts a thread.

      + urtThreadStart (thread : urt_osThread_t*, prio : urt_osThreadPrio_t, arg : void*) : void

        'The calling threads yields.

      + urtThreadYield (void) : void

        'Retrieves the priority of a thread.

      + urtThreadGetPriority (thread : urt_osThread_t*) : urt_osThreadPrio_t

        'Sets the priority of a thread.

      + urtThreadSetPriority (thread : urt_osThread_t*, prio : urt_osThreadPrio_t) : void

        'Retrieves the first thread in the list of children.

      + urtThreadSuspend (void) : void

        'Wakes a suspended thread.

      + urtThreadResume (thread : urt_osThread_t*) : urt_status_t

        'Suspends the calling thread for the specified time.

      + urtThreadSleep (seconds : float) : void

        'Suspends the calling thread for the specified time.

      + urtThreadSSleep (seconds : usnigned int) : void

        'Suspends the calling thread for the specified time.

      + urtThreadMSleep (milliseconds : unsigned int) : void

        'Suspends the calling thread for the specified time.

      + urtThreadUSleep (microseconds : unsigned int) : void

        'Suspends the calling thread until the specified time.

      + urtThreadSleepUntil (time : urt_osTime_t) : void

        'The calling thread exits execution (terminates).

      + urtThreadExit (void) : void

        'Terminates a specified thread.

      + urtThreadTerminate (thread : urt_osThread_t*, sig : urt_osThreadTerminateSignal_t) : void

        'Waits until the specified thread terminates.

      + urtThreadJoin (thread : urt_osThread_t*) : void

        'Retrieves the execution state of the specified thread.

      + urtThreadGetState (thread : urt_osThread_t*) : urt_osThreadState_t

        'Retrieves the first child of a thread (or ""NULL"").

      + urtThreadGetChildren (thread : urt_osThread_t*) : urt_osThread_t*

        'Retrieves a sibling (next child in a list) of the thread or ""NULL"".

      + urtThreadGetSibling (thread : urt_osThread_t*) : urt_psThread_t*

    }

    urt_osThread_t ..> urt_osThreadPrio_t

    urt_osThread_t ..> urt_osThreadFunction_t

    urt_osThread_t ..> urt_osTime_t

    urt_osThread_t ..> urt_osThreadTerminateSignal_t

    urt_osThread_t ..> urt_osThreadState_t

  } /' package "thread" '/

  package "events" {

    /' OS event mask type. '/

    class urt_osEventMask_t <<(T,lightblue)>> {

        'The event mask, which will be handled with maximum priority by the event system.

      + URT_EVENTMASK_MAXPRIO : urt_osEventMask_t

    }

    /' OS event flag type. '/

    class urt_osEventFlags_t <<(T,lightblue)>>

    enum urt_osEventWaitType_t {

      URT_EVENT_WAIT_ONE = 0

      URT_EVENT_WAIT_ANY = 1

      URT_EVENT_WAIT_ALL = 2

    }

    /' OS event listener interface. '/

    class urt_osEventListener_t <<(T,lightblue)>> {

        'Initializes an urt_osEventListener_t object.

      + urtEventListenerInit (listener : urt_osEventListener_t*) : void

        'Retrieves the flags of the event listener.

      + urtEventListenerGetFlags (listener : urt_osEventListener_t*) : urt_osEventFlags_t

        'Retrieves and clears the flags of the event listener.

      + urtEventListenerClearFlags (listener : urt_osEventListener_t*) : urt_osEventFlags_t

    }

    urt_osEventListener_t ..> urt_osEventFlags_t

    /' OS event source interface. '/

    class urt_osEventSource_t <<(T,lightblue)>> {

        'Initializes an urt_osEventSource_t object.

      + urtEventSourceInit (source : urt_osEventSource_t*) : void

        'Emits an event.

      + urtEventSourceBroadcast (source : urt_osEventSource_t*, flags : urt_osEventFlags_t) : void

    }

    urt_osEventSource_t ..> urt_osEventFlags_t

    /' Not a class/type but a set of static event-related functions. '/

    class urt_events <<(F,white)>> {

        'Registers a lister to a source.

      + urtEventRegister (source : urt_osEventSource_t*, listener : urt_osEventListener_t*, mask : urt_osEventMask_t) : urt_status_t

        'Unregisters a listener from a source.

      + urtEventUnregister (source _ urt_osEventSource_t*, listener : urt_osEventListener_t*) : urt_status_t

        'Blocks the thread until any event occurs or the timeout expires.

      + urtEventWait (type : urt_osEventWaitType_t, timeout : urt_delay_t) : urt_osEventMask_t

    }

    urt_events ..> urt_osEventSource_t

    urt_events ..> urt_osEventListener_t

    urt_events ..> urt_osEventMask_t

    urt_events ..> urt_status_t

    urt_events ..> urt_osEventWaitType_t

    urt_events ..> urt_delay_t

  } /' package "events" '/

  /' Not a class/type but a set of output-related functions. '/

    class urt_streams <<(F,white)>> {

        'Prints a formatted string to the standard output stream (stdout).

      + urtPrintf(fmt : char*, ... ) : int

        'Prints a formatted string to the standard error stream (stderr).

      + urtErrPrintf(fmt : char*, ... ) : int

    }

} /' package "interfaces" '/

package "middleware" {

  package "real-time class" {

    /' The top level RT class structure. '/

    class urt_rtclass_t <<(S,lightgrey)>> {

        'The actual RT class.

      + class : urt_rtclasstype_t

        'Parameters of the RT class.

      + params : urt_rtclassparams_t

    }

    urt_rtclass_t "1" *-- "1" urt_rtclasstype_t

    urt_rtclass_t "1" *-- "1" urt_rtclassparams_t

    /' Descriptor to distinguish the four RT classes. '/

    enum urt_rtclasstype_t {

      'Hard real-time.

      URT_RTCLASS_HARD = 0

      'Firm real-time.

      URT_RTCLASS_FIRM = 1

      'Soft real-time.

      URT_RTCLASS_SOFT = 2

      'No real-time at all.

      URT_RTCLASS_NONE = 3

    }

    /' Union structure, holding RT class parameters. '/

    class urt_rtclassparams_t <<(U,lightgreen)>> {

        'Parameters for hard real-time.

      + hrt : urt_hrtparams_t

        'Parameters for firm real-time.

      + frt : urt_frtparams_t

        'Parameters for soft real-time.

      + srt : urt_srtparans_t

        'Parameters for non-real-time.

      + nrt : urt_nrtparams_t

    }

    urt_rtclassparams_t "1" *-- "0..1" urt_hrtparams_t

    urt_rtclassparams_t "1" *-- "0..1" urt_frtparams_t

    urt_rtclassparams_t "1" *-- "0..1" urt_srtparams_t

    urt_rtclassparams_t "1" *-- "0..1" urt_nrtparams_t

    /' Parameters for hard real-time. '/

    class urt_hrtparams_t <<(S,lightgrey)>> {

        'Maximum temporal offset between creation and consumption of messages.

      + deadlineOffset : urt_delay_t

        'Expected rate at which data is published.

      + expectedRate : urt_delay_t

        'QoS timer to detected missed deadlines.

      + qosTimer : urt_osTimer_t

    }

    urt_hrtparams_t ..> urt_delay_t

    urt_hrtparams_t "1" *-- "1" urt_osTimer_t

    /' Parameters for firm real-time. '/

    class urt_frtparams_t <<(S,lightgrey)>> {

        'Maximum temporal offset between creation and consumption of messages.

      + deadlineOffset : urt_delay_t

        'Expected rate at which data is published.

      + expectedRate : urt_delay_t

        'QoS Timer to detect missed deadlines.

      + qosTimer : urt_osTimer_t

        'Callback function for the QoS timer.

      + callback : urt_osTimerCallback_t

        'Parameters for the callback function.

      + cbparams : void*

    }

    urt_frtparams_t ..> urt_delay_t

    urt_frtparams_t "1" *-- "1" urt_osTimer_t

    urt_frtparams_t "1" *-- "1" urt_osTimerCallback_t

    /' Parameters for soft real-time. '/

    class urt_srtparams_t <<(S,lightgrey)>> {

        'Callback function to calculate usefulness given a dleay.

      + *usefulness (dt : urt_delay_t, params : void*) : float

        'Optional parameters for the callback function.

      + params : void*

    }

    urt_srtparams_t ..> urt_delay_t

    /' Parameters for non-real-time. '/

    class urt_nrtparams_t <<(S,lightgrey)>> {

      'There are nor parameters in this case.

    }

  } /' package "real-time class" '/

  /' Message type. '/

  class urt_message_t <<(S,lightgrey)>> {

      'Pointer to the next message in a list.

    + next : urt_message_t*

      'Pointer to some arbitrary (reusable) payload object.

    + payload : void*

      'Origin time of the message.

    + originTime : urt_osTime_t

      'Mutex lock for exclusive access.

    + lock : urt_osMutex_t

      'Counter of HRT subscribers that did not consume the message yet.

    + numHrtConsumersLeft : unsigned int

      'Condition variable to inform waiting publishers when the message is available again.

    + hrtConsumersLeft : urt_osCondvar_t

    -- evaluation data --

      'Counter of overall subscribers that did not consume the message yet.

    + numConsumersLeft : unsigned int

    __

      'Initializes a urt_message_t object.

    + urtMessageInit (message : urt_message_t*, payload : void*) : urt_status_t

  }

  urt_message_t "1" o-- "0..1" urt_message_t

  urt_message_t "1" *-- "1" urt_osTime_t

  urt_message_t "1" *-- "1" urt_osMutex_t

  urt_message_t "1" *-- "1" urt_osCondvar_t

  /' Subscriber type. '/

  class urt_subscriber_t <<(S,lightgrey)>> {

      'Pointer to the next subscriber in a list.

    + next : urt_subscriber_t*

      'Pointer to the topic, this subscriber subscribed to.

    + topic : urt_topic_t*

      'Event listener to notify the node about new messages.

    + evtListener : urt_osEventListener_t

      'Real-time class descriptor.

    + rtclass : urt_rtclass_t

      'Pointer to the message consumed most recently.

    + lastMessage : urt_message_t*

      'Copy of the origin time of the message consumed most recently.

    + lastMessageTime : urt_osTime_t

    -- evaluation data --

      'Minimum latency ever detected.

    + minLatency : urt_delay_t

      'Maximum latency ever detected.

    + maxLatency : urt_delay_t

      'Sum of all latencies.

    + sumLatencies : uint64_t

      'Number of messages received.

    + numMessagesReceived : unsigned int

    __

      'Initializes a urt_subscriber_t object.

    + urtSubscriberInit (subscriber : urt_subscriber_t*) : urt_status_t

      'Tries to subscribe to a topic and contributes an optional list of messages.

    + urtSubscriberSubscribe (subscriber : urt_subscriber_t*, topic : urt_topic_t*, rtclass : urt_rtclass_t*, messages : urt_messages_t*) : urt_status_t

      'Unsubscribes from a topic.

    + urtSubscriberUnsubscribe (subscriber : urt_subscriber_t*) : urt_status_t

      'Fetches either the next or the latest message.

    + urtSubscriberFetchMessage (subscriber : urt_subscriber_t*, latest : bool) : urt_status_t

  }

  urt_subscriber_t "1" o-- "0..1" urt_subscriber_t

  urt_subscriber_t "1" o-- "0..1" urt_topic_t

  urt_subscriber_t "1" *-- "1" urt_osEventListener_t

  urt_subscriber_t "1" *-- "1" urt_rtclass_t

  urt_subscriber_t "1" o-- "0..1" urt_message_t

  urt_subscriber_t "1" *-- "1" urt_osTime_t

  urt_subscriber_t "1" *-- "2" urt_delay_t

  urt_subscriber_t ..> urt_status_t

  urt_subscriber_t ..> urt_topicid_t

  /' Publisher type. '/

  class urt_publisher_t <<(S,lightgrey)>> {

      'Pointer to the topic for publishing.

    + topic : urt_topic_t*

    -- evaluation data --

      'Counter of attempts to publish a message.

    + publishAttempts : unsigned int

      'Counter of failed attempts to publish a message.

    + publishFails : unsigned int

    __

      'Initializes a urt_publisher_t object and contributes an optional list of messages.

    + urtPublisherInit (publisher : urt_publisher_t*, topic : urt_topic_t*, messages : urt_message_t*) : urt_status_t

      'Publishes a message via the associated topic.

    + urtPublisherPublish (publisher : urt_publisher_t*, payload : void*, n : size_t, t : urt_osTime_t, timeout : urt_delay_t) : urt_status_t

  }

  urt_publisher_t "1" o-- "1" urt_topic_t

  urt_publisher_t ..> urt_message_t

  urt_publisher_t ..> urt_osTime_t

  urt_publisher_t ..> urt_delay_t

  urt_publisher_t ..> urt_status_t

  /' Topic type. '/

  class urt_topic_t <<(S,lightgrey)>> {

      'Pointer to the next topic in a list.

    + next : urt_topic_t*

      'Mutex lock for exclusive access.

    + lock : urt_osMutex_t

      'Event source to inform all subscribers when a new message is published.

    + evtSource : urt_osEventSource_t

      'Number of HRT subscribers.

    + numHrtSubscribers : unsigned int

      'List of HRT subscribers, orderd by their expected rate (most critical first).

    + hrtSubscribers : urt_subscriber_t*

      'Timer to check for missed rates.

    + qosTimer : urt_osTimer_t

      'Mandatory message, each Topic holds.

    + mandatoryMessage : urt_message_t

      'Pointer to the latest message.

    + latestMessage : urt_message_t*

      'Identifier of the topic.

    + id : urt_topicid_t

    -- evaluation data --

      'Variable to count how many (non-hrt) subscribers did not fetch a message before it was reused.

    + numDiscardedMessages : unsigned int

      'Number of overall subscribers.

    + numSubscribers : unsigned int

    __

      'Initializes an urt_topic_t object.

    + urtTopicInit (topic : urt_topic_t*, id : urt_topicid_t) : urt_status_t

  }

  urt_topic_t "1" o-- "0..1" urt_topic_t

  urt_topic_t "1" *-- "1" urt_osMutex_t

  urt_topic_t "1" *-- "1" urt_osEventSource_t

  urt_topic_t "1" o-- "0..*" urt_subscriber_t

  urt_topic_t "1" *-- "1" urt_osTimer_t

  urt_topic_t "1" o-- "1..*" urt_message_t

  urt_topic_t "1" *-- "1" urt_message_t

  urt_topic_t "1" *-- "1" urt_topicid_t

  urt_topic_t ..> urt_osTime_t

  urt_topic_t ..> urt_status_t

  /' uRtWare core type. '/

  class urt_core_t <<(S,lightgrey)>> {

      'List of nodes ordered by their (initial) priority.

    - {static} _nodes : urt_node_t*

      'List of topics ordered by their identifiers.

    - {static} _topics : urt_topic_t*

      'Event source for control events.

    - {static} _evtSource : urt_osEventSource_t

      'Mutex used for synchronization.

    - {static} _lock : urt_osMutex_t

    __

      'Initializes the urt_core_t object.

    + urtCoreInit (void) : urt_status_t

      'Starts all node threads (nodes will block before the loop).

    + urtCoreStartNodes (void) : urt_status_t

      'Nodes can use this function to synchronize globally.

    + urtCoreSynchronizeNodes (node : urt_node_t*, stage : urt_nodesync_t) : urt_status_t

      'Stops all nodes.

    + urtCoreStopNodes (void) : urt_status_t

      'Retrieves a topic given an identifier.

    + urtCoreRetrieveTopic (id : urt_topicid_t) : urt_topic_t*

  }

  urt_core_t "1" o-- "0..*" urt_topic_t

  urt_core_t "1" o-- "0..*" urt_node_t

  urt_core_t "1" *-- "1" urt_osEventSource_t

  urt_core_t "1" *-- "1" urt_osMutex_t

  urt_core_t ..> urt_status_t

  urt_core_t --> urt_nodesync_t

  urt_core_t ..> urt_topicid_t

  package "node" {

    /' Function type to be called during setup phase of node threads. '/

    class urt_nodeSetupCallback_t <<(T,lightblue)>> {

      'Takes the node and optional parameters as arguments and returns a event mask for the next iteration.

      urt_nodeSetupCallback_t (node : urt_node_t*, arg : void*) : urt_osEventMask_t

    }

    urt_nodeSetupCallback_t ..> urt_node_t

    urt_nodeSetupCallback_t ..> urt_status_t

    /' Function type to be called during loop phase of node threads. '/

    class urt_nodeLoopCallback_t <<(T,lightblue)>> {

      'Takes the node, a mask of occurred events and optional parameters as arguments and returns a event mask for the next iteration.

      urt_nodeLoopCallback_t (node : urt_node_t*, events : urt_osEventMask_t, arg : void*) : urt_osEventMask_t

    }

    urt_nodeLoopCallback_t ..> urt_node_t

    urt_nodeLoopCallback_t ..> urt_osEventMask_t

    urt_nodeLoopCallback_t ..> urt_status_t

    /' Node type. '/

    class urt_node_t <<(S,lightgrey)>> {

        'Pointer to the next node in a list.

      + next : urt_node_t*

        'Pointer to the nore thread.

      + thread : urt_osThread_t*

        'Callback function to be called during the setup phase.

      + setupcallback : urt_nodeSetupCallback_t*

        'Optional parameters for the setup callback function.

      + setupparams : void*

        'Callback function to be called in each loop iteration.

      + loopcallback : urt_nodeLoopCallback_t*

        'Optional parameters for the loop callback function.

      + loopparams : void*

        'Execution stage of the node.

      + stage : urt_nodesync_t

        'Event listener for middleware-wide control events.

      + listener : urt_osEventListener_t

      __

      'The main() function of the node thread.

      - {static} _main : urt_osThreadFunction_t

        'Initializes an urt_node_t object.

      + urtNodeInit (node : urt_node_t*, stacksize : size_t, setupcallback : urt_nodeSetupCallback_t*, setupparams : void*, loopcallback : urt_nodeLoopCallback_t*, loopparams : void*) : urt_status_t

    }

    urt_node_t "1" o-- "0..1" urt_node_t

    urt_node_t "1" o-- "1" urt_osThread_t

    urt_node_t "1" o-- "1" urt_nodeSetupCallback_t

    urt_node_t "1" o-- "1" urt_nodeLoopCallback_t

    urt_node_t "1" *-- "1" urt_nodesync_t

    urt_node_t "1" *-- "1" urt_osEventMask_t

    urt_node_t "1" *-- "1" urt_osEventWaitType_t

    urt_node_t "1" *-- "1" urt_osEventListener_t

    urt_node_t ..> urt_osThreadTerminateSignal_t

  } /' package "node" '/

} /' package "middleware" '/

@enduml