urtware / doc / activitydiagrams / subscriber / urtSubscriberFetchNextMessage.uml @ c22d21ad
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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..2020 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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|
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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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'/ |
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/'### INTRO ##################################################################'/ |
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@startuml |
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title **µRtWare**\nurtSubscriberFetchNextMessage()\n |
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!include ../../functions.iuml |
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/'### PARAMETERS & START #####################################################'/ |
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start |
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note |
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-- ""**subscriber** : urt_subscriber_t*"" -- |
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The subscriber that shall fetch the message. |
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Must not be ""NULL"". |
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-- ""**payload** : void*"" -- |
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Pointer where to copy the payload to. |
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May be ""NULL"" for messages without payload. |
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-- ""**bytes** : size_t"" -- |
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Payload size in bytes. |
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-- ""**latency** : urt_delay_t*"" -- |
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The latency can be returned by reference. |
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May be ""NULL"". |
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end note |
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/'### PROCEDURE ##############################################################'/ |
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:lock topic; |
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if (Is HRT subscriber?) then (yes) |
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:access next message; |
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else (no) |
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if (Has a message been read before?) then (yes) |
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:access last read message; |
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if (Message 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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:access next message; |
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while (Timestamp of next message is younger than of current?) is (yes) |
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:iterate by one message; |
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endwhile (no) |
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} |
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endif |
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else (no) |
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:access message after topic's latest message; |
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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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fork |
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:copy timestamp of message; |
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fork again |
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if (Optional output argument "latency" given?) then (yes) |
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:set latency value (now - message origin time); |
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else (no) |
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endif |
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endfork |
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fork again |
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:copy message payload; |
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fork again |
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if (Is HRT subscriber?) then (yes) |
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fork |
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:decrement HRT counter of current message; |
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if (HRT counter became 0?) then (yes) |
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:signal topic's condition variable; |
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else (no) |
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endif |
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fork again |
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:update QoS delay timer (@subscriber); |
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endfork |
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else (no) |
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endif |
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endfork |
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:unlock topic; |
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/'### STOP & RETURN ##########################################################'/ |
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stop |
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note |
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-- **return** ""urt_status_t"" -- |
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Returns ""URT_STATUS_OK"". |
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end note |
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/'### OUTRO ##################################################################'/ |
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@enduml |