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..2020  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/>.

'/

/'### INTRO ##################################################################'/

@startuml

title **µRtWare**\nurtNrtSubscriberFetchLatestMessage()\n

!include ../functions.iuml

/'### PARAMETERS & RETURN ####################################################'/

note

  -- **subscriber** : urt_nrtsubscriber_t* --

  The NRT subscriber that shall fetch the message.

  Must not be ""NULL"".

  -- **payload** : void* --

  Pointer where to copy the payload to.

  May be ""NULL"" for messages without payload.

  -- **bytes** : size_t --

  Payload size in bytes.

  -- **latency** : urt_delay_t* --

  The latency can be returned by reference.

  May be ""NULL"".

  ====

  -- **return** : urt_status_t --

  Returns ""URT_STATUS_OK"" on success.

  Returns ""URT_STATUS_FETCH_NOTOPIC"" if the subscriber is not associated to a topic.

  Retruns ""URT_STATUS_FETCH_NOMESSAGE"" if there is no new message to fetch.

endnote

/'### PROCEDURE ##############################################################'/

start

if (Associated to a topic?) then (yes)

  :lock topic;

  $find_latest_message()

  if (Timestamp equals local copy?) then (yes)

    :unlock topic;

    stop

    note

      Returns ""URT_STATUS_FETCH_NOMESSAGE"".

    endnote

  else (no)

    fork

      $fetch_message()

    fork again

      :calculate message latency;

      note

        Can be optimized in case all flags are disabled.

      endnote

      fork

        #EEEEEE:..//URT_CFG_PUBSUB_PROFILING == true//..\naccumulate ""sumLatencies"" value;

      fork again

        partition "//URT_CFG_PUBSUB_PROFILING == true//" #EEEEEE {

          if (Latency is lower than ""minLatency""?) then (yes)

            #EEEEEE:update ""minLatency"" value;

          elseif (Latency is greater than ""maxLatency""?) then (yes)

            #EEEEEE:update ""maxLatency"" value;

          else (no)

          endif

        }

      fork again

        if (Optional ""latency"" output argument given?) then (yes)

          :set ""latency"" value;

        else (no)

        endif

      fork again

      endfork

    endfork

    :unlock topic;

    stop

    note

      Returns ""URT_STATUS_OK"".

    endnote

  endif

else (no)

  stop

  note

    Returns ""URT_STATUS_FETCH_NOTOPIC"".

  endnote

endif

/'### OUTRO ##################################################################'/

@enduml