src/BallastDumpManager.cpp

   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 #include "BallastDumpManager.hpp"
  25 #include "Engine/GlideSolvers/GlidePolar.hpp"
  26
  27 void
  28 BallastDumpManager::Start()
  29 {
  30   assert(!IsEnabled());
  31   enabled = true;
  32
  33   // Update ballast_clock for the next call to BallastDumpManager::Update()
  34   ballast_clock.Update();
  35 }
  36
  37 void
  38 BallastDumpManager::Stop()
  39 {
  40   assert(IsEnabled());
  41   enabled = false;
  42 }
  43
  44 void
  45 BallastDumpManager::SetEnabled(bool _enabled)
  46 {
  47   if (_enabled && !IsEnabled())
  48     Start();
  49   else if (!_enabled && IsEnabled())
  50     Stop();
  51 }
  52
  53 bool
  54 BallastDumpManager::Update(GlidePolar &glide_polar, unsigned dump_time)
  55 {
  56   assert(IsEnabled());
  57
  58   // We don't know how fast the water is flowing so don't pretend that we do
  59   if (dump_time == 0) {
  60     Stop();
  61     return false;
  62   }
  63
  64   // Milliseconds since last ballast_clock.Update() call
  65   int dt = ballast_clock.Elapsed();
  66
  67   // Update ballast_clock for the next call to BallastDumpManager::Update()
  68   ballast_clock.Update();
  69
  70   // How many percent of the max. ballast do we dump in one millisecond
  71   fixed percent_per_millisecond = fixed(1) / (1000 * dump_time);
  72
  73   // Calculate the new ballast percentage
  74   fixed ballast = glide_polar.GetBallast() - dt * percent_per_millisecond;
  75
  76   // Check if the plane is dry now
  77   if (negative(ballast)) {
  78     Stop();
  79     glide_polar.SetBallastLitres(fixed(0));
  80     return false;
  81   }
  82
  83   // Set new ballast
  84   glide_polar.SetBallast(ballast);
  85   return true;
  86 }