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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 | <html><!-- #BeginTemplate "/Templates/tmpl.dwt" --><!-- DW6 --><head><!-- #BeginEditable "doctitle" --><title>PTypes: multithreading: jobqueue</title><!-- #EndEditable --><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link rel="stylesheet" href="styles.css"></head><body bgcolor="#FFFFFF" leftmargin="40" marginwidth="40"><p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a> <hr size="1" noshade><!-- #BeginEditable "body" --><p class="hpath"><a href="index.html">Top</a>: <a href="async.html">Multithreading</a>: jobqueue</p><blockquote> <pre class="lang">#include <pasync.h>class jobqueue { jobqueue(int limit = DEF_QUEUE_LIMIT); void post(message* msg); void post(int id, int param = 0); void posturgent(message* msg); void posturgent(int id, int param = 0); message* getmessage(int timeout = -1); int get_count(); int get_limit();}</pre></blockquote><p>The <span class="lang">jobqueue</span> class implements a thread-safe list of objects of type <span class="lang"><a href="async.message.html">message</a></span> or any derivative class. <span class="lang">Jobqueue</span> supports posting to and reading from the list from multiple threads simultaneously.</p><p>The <span class="lang">jobqueue</span> class can help to build multithreaded server/robot applications by maintaining a pool of reusable threads that receive job 'assignments' from a queue. This threading model can be faster compared to applications that create and destroy separate thread objects for each task. See <a href="async.examples.html">Examples</a> for a full-featured server template with a thread pool.</p><p><span class="def">jobqueue::jobqueue(int limit = DEF_QUEUE_LIMIT)</span> constructs a job queue object. <span class="lang">Limit</span> specifies the maximum number of messages this queue can hold. If the limit is reached, the next thread that posts a message will wait until the queue becomes available again. In this version the default for <span class="def">limit</span> is 5000.</p><p><span class="def">void jobqueue::post(message* msg)</span> adds a message to the queue. <span class="lang">Msg</span> can be an object of class <span class="lang">message</span> or any derivative class. The <span class="lang">message</span> object should always be created dynamically using operator <span class="lang">new</span>. The messages in the queue are processed in order they were posted, i.e. on first-in-first-out basis.</p><p><span class="def">void jobqueue::post(int id, pintptr param = 0)</span> creates a message object using <span class="lang">id</span> and <span class="lang">param</span> and calls <span class="lang">post(message*)</span>.</p><p><span class="def">void msgqueue::posturgent(message* msg)</span> posts a message object "out of turn", i.e. this message will be processed first. The messages posted through this method are processed on first-in-last-out basis. <span class="lang">post()</span> and <span class="lang">posturgent()</span> can be used alternately on the same queue.</p><p><span class="def">void jobqueue::posturgent(int id, pintptr param = 0)</span> creates a message object using <span class="lang">id</span> and <span class="lang">param</span> and calls <span class="lang">posturgent(message*)</span>.</p><p><span class="def">message* jobqueue::getmessage(int timeout = -1)</span> retrieves the next message from the queue or waits if there are no messages available. The <span class="lang">timeout</span> parameter specifies the timeout value in milliseconds. If <span class="lang">timeout</span> is -1 (the default) <span class="lang">getmessage()</span> will wait for a message infinitely. This function returns a message object, or otherwise <span class="lang">NULL</span> if the time specified in <span class="lang">timeout</span> has elapsed. <b>NOTE</b>: the message object returned by this function must be freed with operator <span class="lang">delete</span>. It is safe to call <span class="lang">getmessage()</span> concurrently.</p><p><span class="def">int jobqueue::get_count()</span> returns the number of messages currently in the queue.</p><p><span class="def">int jobqueue::get_limit()</span> returns the queue limit set by the constructor.</p><p class="seealso">See also: <a href="async.message.html">message</a>, <a href="async.msgqueue.html">msgqueue</a>, <a href="async.examples.html">Examples</a></p><span class="lang"></span><!-- #EndEditable --><hr size="1"><a href="../index.html" class="ns">PTypes home</a></body><!-- #EndTemplate --></html> |
