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common/rfb/Timer.h

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+/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
+ * Copyright 2018 Pierre Ossman for Cendio AB
+ * 
+ * This 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 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software 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 software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+#ifndef __RFB_TIMER_H__
+#define __RFB_TIMER_H__
+
+#include <list>
+#ifdef WIN32
+#include <winsock2.h>
+#else
+#include <sys/time.h>
+#endif
+
+namespace rfb {
+
+  /* Timer
+
+     Cross-platform timeout handling.  The caller creates instances of Timer and passes a
+     Callback implementation to each.  The Callback will then be called with a pointer to
+     the Timer instance that timed-out when the timeout occurs.
+
+     The static methods of Timer are used by the main loop of the application both to
+     dispatch elapsed Timer callbacks and to determine how long to wait in select() for
+     the next timeout to occur.
+
+  */
+
+  struct Timer {
+
+    struct Callback {
+      // handleTimeout
+      //   Passed a pointer to the Timer that has timed out.  If the handler returns true
+      //   then the Timer is reset and left running, causing another timeout after the
+      //   appropriate interval.
+      //   If the handler returns false then the Timer is cancelled.
+      virtual bool handleTimeout(Timer* t) = 0;
+
+      virtual ~Callback() {}
+    };
+
+    // checkTimeouts()
+    //   Dispatches any elapsed Timers, and returns the number of milliseconds until the
+    //   next Timer will timeout.
+    static int checkTimeouts();
+
+    // getNextTimeout()
+    //   Returns the number of milliseconds until the next timeout, without dispatching
+    //   any elapsed Timers.
+    static int getNextTimeout();
+
+    // Create a Timer with the specified callback handler
+    Timer(Callback* cb_) {cb = cb_;}
+    ~Timer() {stop();}
+
+    // startTimer
+    //   Starts the timer, causing a timeout after the specified number of milliseconds.
+    //   If the timer is already active then it will be implicitly cancelled and re-started.
+    void start(int timeoutMs_);
+
+    // stopTimer
+    //   Cancels the timer.
+    void stop();
+
+    // isStarted
+    //   Determines whether the timer is started.
+    bool isStarted();
+
+    // getTimeoutMs
+    //   Determines the previously used timeout value, if any.
+    //   Usually used with isStarted() to get the _current_ timeout.
+    int getTimeoutMs();
+
+    // getRemainingMs
+    //   Determines how many milliseconds are left before the Timer
+    //   will timeout. Only valid for an active timer.
+    int getRemainingMs();
+
+    // isBefore
+    //   Determine whether the Timer will timeout before the specified time.
+    bool isBefore(timeval other);
+
+  protected:
+    timeval dueTime;
+    int timeoutMs;
+    Callback* cb;
+
+    static void insertTimer(Timer* t);
+    // The list of currently active Timers, ordered by time left until timeout.
+    static std::list<Timer*> pending;
+  };
+
+};
+
+#endif