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urtware / doc / statediagrams / subscriber / urtSubscriberFetchMessage.uml @ e98c61a8

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/'
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µRtWare is a lightweight publish/subscribe middleware for real-time
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applications. It was developed as part of the software habitat for the
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Autonomous Mini Robot [1] (AMiRo) but can be used for other purposes as well.
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Copyright (C) 2018..2018  Thomas Schöpping et al.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program.  If not, see <http://www.gnu.org/licenses/>.
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'/
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@startuml
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title **µRtWare**\nurtSubscriberFetchMessage()\n
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start
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note
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  event received
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endnote
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:lock topic;
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note
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  The message list is part of the topic and must be locked.
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endnote
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if (Is HRT subscriber?) then (yes)
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  :lock next message;
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  if (Fetch next or latest message?) then (next)
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  else (latest)
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    partition "iterate to latest" {
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      :lock next message;
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      note
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        locked two messaged ahead
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      endnote
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      while (Timestamp of next message is younger than current?) is (yes)
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        fork
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          fork
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            :decremenet HRT counter of current message;
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          fork again
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            :update QoS delay timer (@subscriber);
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            note
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              no lock required since this timer is only accessed when the topic is locked
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            endnote
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          endfork
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          :unlock current message;
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        fork again
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          :lock next message;
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        endfork
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      endwhile (no)
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      :unlock next message;
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      note
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        one message ahead still locked
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        but HRT counter not yet decremented
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      endnote
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    }
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  endif
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  fork
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    :decrement HRT counter of current message;
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  fork again
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    :update QoS delay timer (@subscriber);
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    note
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      no lock required since this timer is only accessed when the topic is locked
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    endnote
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  endfork
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else (no)
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  :lock last read message;
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  if (Timestamp equals local copy?) then (yes)
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  else (no)
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    partition "find oldest valid message" {
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      :lock next message;
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      while (Timestamp of next is younger then of current?) is (yes)
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        fork
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          :unlock current mesage;
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        fork again
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          :lock one message further ahaead;
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        endfork
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      endwhile (no)
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      :unlock next message;
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    }
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  endif
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  if (Fetch next or latest message?) then (next)
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  else (latest)
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    partition "iterate to latest" {
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      :lock next message;
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      while (Timestamp of next message is younger then current?) is (yes)
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        fork
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          :unlock current message;
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        fork again
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          :lock next message;
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        endfork
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      endwhile (no)
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      :unlock next message;
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      note
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        one message ahead still locked
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      endnote
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    }
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  endif
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endif
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fork
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  :set last fetched message pointer to locked message;
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fork again
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  :copy timestamp of message;
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fork again
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  if (Copy of payload requested?) then (yes)
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    :copy message payload;
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  else (no)
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  endif
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endfork
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:unlock message;
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:unlock topic;
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stop
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@enduml