urtware / doc / statediagrams / subscriber / urtSubscriberFetchMessage.uml @ 35c9457f
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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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|
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Copyright (C) 2018..2018 Thomas Schöpping et al. |
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|
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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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|
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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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|
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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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@startuml |
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|
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title **µRtWare**\nurtSubscriberFetchMessage()\n |
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|
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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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endfork |
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:unlock message; |
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:unlock topic; |
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stop |
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@enduml |