annotate base/Scavenger.h @ 76:af2725b5d6fe

* Implement harmonic cursor in spectrogram
* Implement layer export.  This doesn't quite do the right thing for the SV
  XML layer export yet -- it doesn't include layer display information, so
  when imported, it only creates an invisible model.  Could also do with
  fixing CSV file import so as to work correctly for note and text layers.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    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 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

/*
   This is a modified version of a source file from the 
   Rosegarden MIDI and audio sequencer and notation editor.
   This file copyright 2000-2006 Chris Cannam.
*/

#ifndef _SCAVENGER_H_
#define _SCAVENGER_H_

#include "System.h"

#include <vector>
#include <sys/time.h>

/**
 * A very simple class that facilitates running things like plugins
 * without locking, by collecting unwanted objects and deleting them
 * after a delay so as to be sure nobody's in the middle of using
 * them.  Requires scavenge() to be called regularly from a non-RT
 * thread.
 *
 * This is currently not at all suitable for large numbers of objects
 * -- it's just a quick hack for use with things like plugins.
 */

template <typename T>
class Scavenger
{
public:
    Scavenger(int sec = 2, int defaultObjectListSize = 200);

    /**
     * Call from an RT thread etc., to pass ownership of t to us.
     * Only one thread should be calling this on any given scavenger.
     */
    void claim(T *t);

    /**
     * Call from a non-RT thread.
     * Only one thread should be calling this on any given scavenger.
     */
    void scavenge(bool clearNow = false);

protected:
    typedef std::pair<T *, int> ObjectTimePair;
    typedef std::vector<ObjectTimePair> ObjectTimeList;
    ObjectTimeList m_objects;
    int m_sec;

    unsigned int m_claimed;
    unsigned int m_scavenged;
};

/**
 * A wrapper to permit arrays to be scavenged.
 */

template <typename T>
class ScavengerArrayWrapper
{
public:
    ScavengerArrayWrapper(T *array) : m_array(array) { }
    ~ScavengerArrayWrapper() { delete[] m_array; }

private:
    T *m_array;
};


template <typename T>
Scavenger<T>::Scavenger(int sec, int defaultObjectListSize) :
    m_objects(ObjectTimeList(defaultObjectListSize)),
    m_sec(sec),
    m_claimed(0),
    m_scavenged(0)
{
}

template <typename T>
void
Scavenger<T>::claim(T *t)
{
//    std::cerr << "Scavenger::claim(" << t << ")" << std::endl;

    struct timeval tv;
    (void)gettimeofday(&tv, 0);
    int sec = tv.tv_sec;

    for (size_t i = 0; i < m_objects.size(); ++i) {
	ObjectTimePair &pair = m_objects[i];
	if (pair.first == 0) {
	    pair.second = sec;
	    pair.first = t;
	    ++m_claimed;
	    return;
	}
    }

    // Oh no -- run out of slots!  Warn and discard something at
    // random (without deleting it -- it's probably safer to leak).

    for (size_t i = 0; i < m_objects.size(); ++i) {
	ObjectTimePair &pair = m_objects[i];
	if (pair.first != 0) {
	    pair.second = sec;
	    pair.first = t;
	    ++m_claimed;
	    ++m_scavenged;
	}
    }
}

template <typename T>
void
Scavenger<T>::scavenge(bool clearNow)
{
//    std::cerr << "Scavenger::scavenge: scavenged " << m_scavenged << ", claimed " << m_claimed << std::endl;

    if (m_scavenged >= m_claimed) return;
    
    struct timeval tv;
    (void)gettimeofday(&tv, 0);
    int sec = tv.tv_sec;

    for (size_t i = 0; i < m_objects.size(); ++i) {
	ObjectTimePair &pair = m_objects[i];
	if (clearNow ||
	    (pair.first != 0 && pair.second + m_sec < sec)) {
	    T *ot = pair.first;
	    pair.first = 0;
	    delete ot;
	    ++m_scavenged;
	}
    }
}

#endif