src/Computer/GPSClock.hpp

   1 /*
   2 Copyright_License {
   3
   4   XCSoar Glide Computer - http://www.xcsoar.org/
   5   Copyright (C) 2000-2013 The XCSoar Project
   6   A detailed list of copyright holders can be found in the file "AUTHORS".
   7
   8   This program is free software; you can redistribute it and/or
   9   modify it under the terms of the GNU General Public License
  10   as published by the Free Software Foundation; either version 2
  11   of the License, or (at your option) any later version.
  12
  13   This program is distributed in the hope that it will be useful,
  14   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16   GNU General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with this program; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21 }
  22 */
  23
  24 #ifndef XCSOAR_GPS_CLOCK_HPP
  25 #define XCSOAR_GPS_CLOCK_HPP
  26
  27 #include "Math/fixed.hpp"
  28
  29 /**
  30  * Class for GPS-time based time intervals
  31  */
  32 class GPSClock {
  33 private:
  34   fixed last;
  35   fixed dt;
  36
  37 public:
  38   /**
  39    * Initializes the object, setting the last time stamp to "0",
  40    * i.e. a check() will always succeed.  If you do not want this
  41    * default behaviour, call update() immediately after creating the
  42    * object.
  43    */
  44   GPSClock(const fixed _minstep):last(fixed(0)), dt(_minstep) {}
  45
  46   /**
  47    * Resets the clock.
  48    */
  49   void Reset() {
  50     last = fixed(0);
  51   }
  52
  53   /**
  54    * Updates the clock.
  55    */
  56   void Update(fixed now) {
  57     last = now;
  58   }
  59
  60   /**
  61    * Checks whether the GPS time was reversed
  62    * @param now Current time
  63    * @return True if time has been reversed, False otherwise
  64    */
  65   bool CheckReverse(const fixed now) {
  66     if (now<last) {
  67       Update(now);
  68       return true;
  69     } else {
  70       return false;
  71     }
  72   }
  73
  74   /**
  75    * Set dt to a new value defined by _dt
  76    * @param _dt The new value fot dt
  77    */
  78   void SetDT(const fixed _dt) {
  79     dt = _dt;
  80   }
  81
  82   /**
  83    * Calls check_advance(fixed, fixed) with dt
  84    * as the default value for dt
  85    * @param now Current time
  86    * @see check_advance(fixed, fixed)
  87    */
  88   bool CheckAdvance(const fixed now) {
  89     return CheckAdvance(now, dt);
  90   }
  91
  92   fixed DeltaAdvance(const fixed now) {
  93     if (CheckReverse(now))
  94       return fixed(-1);
  95
  96     // check if time has advanced past dt
  97     if (now - last >= dt) {
  98       fixed dt = now - last;
  99       Update(now);
 100       return dt;
 101     } else {
 102       return fixed(0);
 103     }
 104   }
 105
 106   /**
 107    * Checks whether the specified duration (dt) has passed since the last
 108    * update. If yes, it updates the time stamp.
 109    * @param now Current time
 110    * @param dt The timestep in milliseconds
 111    * @return
 112    */
 113   bool CheckAdvance(const fixed now, const fixed dt) {
 114     if (CheckReverse(now))
 115       return false;
 116
 117     if (now >= last + dt) {
 118       Update(now);
 119       return true;
 120     } else
 121       return false;
 122   }
 123 };
 124
 125 #endif