include/canvas/elapsedtime.hxx

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  19
  20 #ifndef INCLUDED_CANVAS_ELAPSEDTIME_HXX
  21 #define INCLUDED_CANVAS_ELAPSEDTIME_HXX
  22
  23 #include <canvas/canvastoolsdllapi.h>
  24 #include <memory>
  25
  26 namespace canvas
  27 {
  28     namespace tools
  29     {
  30         /** Calculate elapsed time.
  31
  32             This class provides several time-measurement and
  33             -management functions. In its simplest use-case, it
  34             measures the time from its creation.
  35          */
  36         class CANVASTOOLS_DLLPUBLIC ElapsedTime
  37         {
  38         public:
  39             /** Create a new ElapsedTime object
  40
  41                 The moment of construction starts the time
  42                 measurement. That means, a subsequent getElapsedTime()
  43                 call will return the time difference between object
  44                 creation and getElapsedTime() call.
  45              */
  46             ElapsedTime();
  47
  48             /** Creates a new ElapsedTime object based on another
  49                 timer.
  50
  51                 The moment of construction starts the time
  52                 measurement. That means, a subsequent getElapsedTime()
  53                 call will return the time difference between object
  54                 creation and getElapsedTime() call. All time values
  55                 are not taken from the system's time base, but from
  56                 the provided timer.
  57              */
  58             ElapsedTime( std::shared_ptr<ElapsedTime> const & pTimeBase );
  59
  60             /** Reset the time
  61
  62                 The instance of the reset() call starts the time
  63                 measurement from scratch. That means, a subsequent
  64                 getElapsedTime() call will return the time difference
  65                 between reset() and getElapsedTime() call.
  66              */
  67             void reset();
  68
  69             /** Query the elapsed time
  70
  71                 This method returns the elapsed time in seconds
  72                 between either the construction of this object, or the
  73                 last reset() call, if any (but see the time modulation
  74                 methods below, for means to modify the otherwise
  75                 continuous flow of time).
  76
  77                 @return the elapsed time in seconds.
  78              */
  79             double getElapsedTime() const;
  80
  81             /** Pauses the running timer.
  82
  83                 This method stops the time, as returned by this
  84                 object, until continueTimer() is called. During this
  85                 period, getElapsedTime() will always return the same
  86                 time value (i.e. the instant when pauseTimer() was
  87                 called).
  88              */
  89             void pauseTimer();
  90
  91             /** Continues the paused timer.
  92
  93                 This method re-enables the time flow, that is, time
  94                 starts running again for clients calling
  95                 getElapsedTime(). The (subtle) difference to the
  96                 holdTimer/releaseTimer() methods below is, that there
  97                 is no perceived time 'jump' between the pauseTimer()
  98                 call and the continueTimer() call, i.e. the time
  99                 starts over with the same value it has stopped on
 100                 pauseTimer().
 101              */
 102             void continueTimer();
 103
 104             /** Adjusts the timer, hold and pause times.
 105
 106                 This method modifies the time as returned by this
 107                 object by the specified amount. This affects the time
 108                 as returned by getElapsedTime(), regardless of the
 109                 mode (e.g. paused, or on hold).
 110
 111                 @param fOffset
 112                 This value will be added to the current time, i.e. the
 113                 next call to getElapsedTime() (when performed
 114                 immediately) will be adjusted by fOffset.
 115             */
 116             void adjustTimer( double fOffset );
 117
 118             /** Holds the current time.
 119
 120                 This call makes the timer hold the current time
 121                 (e.g. getElapsedTime() will return the time when
 122                 holdTimer() was called), while the underlying time is
 123                 running on. When releaseTimer() is called, the time
 124                 will 'jump' to the then-current, underlying time. This
 125                 is equivalent to pressing the "interim time" button on
 126                 a stop watch, which shows this stopped time, while the
 127                 clock keeps running internally.
 128             */
 129             void holdTimer();
 130
 131             /** Releases a held timer.
 132
 133                 After this call, the timer again returns the running
 134                 time on getElapsedTime().
 135              */
 136             void releaseTimer();
 137
 138         private:
 139             static double getSystemTime();
 140             double getCurrentTime() const;
 141             double getElapsedTimeImpl() const; // does not set m_fLastQueriedTime
 142
 143             const std::shared_ptr<ElapsedTime>  m_pTimeBase;
 144
 145             /// To validate adjustTimer() calls with bLimitToLastQueriedTime=true
 146             mutable double                          m_fLastQueriedTime;
 147
 148             /// Start time, from which the difference to the time base is returned
 149             double                                  m_fStartTime;
 150
 151             /// Instant, when last pause or hold started, relative to m_fStartTime
 152             double                                  m_fFrozenTime;
 153
 154             /// True, when in pause mode
 155             bool                                    m_bInPauseMode;
 156
 157             /// True, when in hold mode
 158             bool                                    m_bInHoldMode;
 159         };
 160
 161     }
 162 }
 163
 164 #endif /* INCLUDED_CANVAS_ELAPSEDTIME_HXX */
 165
 166 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */