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**\nurtHrtSubscriberFetchLatestMessage()\n

!include ./functions.iuml

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

note

  -- **subscriber** : urt_hrtsubscriber_t* --

  The HRT 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_ERROR"" if the subscriber is not associated to a topic.

endnote

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

start

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

  :lock topic;

  :access last read message;

  while (Timestamp of next message is younger?) is (yes)

    fork

      :proceed to next message;

    fork again

      :decrement next message's HRT counter;

    endfork

  endwhile (no)

  fork

    $fetch_message()

  fork again

    if (The HRT counter of any message became 0?) then (yes)

      :signal topic's condition variable;

    else (no)

    endif

  fork again

    :reset QoS delay timer;

  endfork

  :unlock topic;

  stop

  note

    Returns ""URT_STATUS_OK"".

  endnote

else (no)

  stop

  note

    Returns ""URT_STATUS_ERROR"".

  endnote

endif

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

@enduml