root/libcore/VirtualClock.h

INCLUDED FROM

// VirtualClock.h -- virtual clock for gnash core lib
// 
//   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010,
//   2011 Free Software Foundation, Inc
// 
// This program 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 3 of the License, or
// (at your option) any later version.
// 
// This program 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 program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

#ifndef GNASH_VIRTUAL_CLOCK_H
#define GNASH_VIRTUAL_CLOCK_H

#include <cassert> // for InterruptableVirtualClock

namespace gnash
{

/// A class used to virtualize time flow
//
/// This class will be used to fetch current time
/// everytime it is needed by the core lib.
///
class VirtualClock
{
public:

    /// Return number of milliseconds elapsed since start.
    //
    /// Subclass this to provide time to the core lib.
    //
    /// NOTE:
    /// 32bit unsigned int has an upper limit of 4294967295
    /// which means about 49 days before overlflow.
    ///
    virtual unsigned long int elapsed() const=0;

    /// Restart the clock
    virtual void restart()=0;

    virtual ~VirtualClock() {}
};

/// A VirtualClock wrapper adding pause/resume capabilities 
class InterruptableVirtualClock : public VirtualClock
{

public:

        /// Construct an InterruptableVirtualClock from a VirtualClock source
        //
        /// The interruptable virtual clock starts in 'stop' mode,
    /// use resume() to start.
        ///
        /// @param src
        ///     A VirtualClock to use as source, ownership is retained by caller
    /// which should guarantee to keep the source alive for the whole
    /// lifetime of this instance.
        ///
        InterruptableVirtualClock(VirtualClock& src)
                :
                _src(src),
                _elapsed(0),
                _offset(_src.elapsed()),
                _paused(true)
        {
        }

        /// Return elapsed time, taking interruptions in consideration
        unsigned long int elapsed() const
        {
                if ( ! _paused ) // query source if not stopped
                        _elapsed = _src.elapsed()-_offset;
                return _elapsed;
        }

        void restart()
        {
                _elapsed = 0;
                _offset = _src.elapsed();
        }

        void pause()
        {
                if ( _paused ) return; // nothing to do
                _paused = true;
        }

        void resume()
        {
                if ( ! _paused ) return; // nothing to do
                _paused = false;

                unsigned long now = _src.elapsed();
                _offset = ( now - _elapsed );
                assert( now-_offset == _elapsed ); // check if we did the right thing
        }

private:

        VirtualClock& _src;

        mutable unsigned long int _elapsed;

        unsigned long int _offset;

        bool _paused;
};


} // namespace gnash

#endif // GNASH_VIRTUAL_CLOCK_H