include/canvas/elapsedtime.hxx

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