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// -*- c-basic-offset: 4 -*-
/*
Rosegarden
A sequencer and musical notation editor.
This program is Copyright 2000-2008
Guillaume Laurent <glaurent@telegraph-road.org>,
Chris Cannam <cannam@all-day-breakfast.com>,
Richard Bown <bownie@bownie.com>
The moral right of the authors to claim authorship of this work
has been asserted.
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.
*/
#ifndef _SCAVENGER_H_
#define _SCAVENGER_H_
#include <vector>
#include <list>
#include <sys/time.h>
#include <pthread.h>
#include <iostream>
namespace Rosegarden
{
/**
* 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);
~Scavenger();
/**
* Call from an RT thread etc., to pass ownership of t to us for
* later disposal. Only one thread should be calling this on any
* given scavenger.
*
* This is only lock-free so long as a slot is available in the
* object list; otherwise it takes a lock and allocates memory.
* Scavengers should always be used with an object list size
* sufficient to ensure that enough slots are always available in
* normal use.
*/
void claim(T *t);
/**
* Call from a non-RT thread.
* Only one thread should be calling this on any given scavenger.
*/
void scavenge();
protected:
typedef std::pair<T *, int> ObjectTimePair;
typedef std::vector<ObjectTimePair> ObjectTimeList;
ObjectTimeList m_objects;
int m_sec;
typedef std::list<T *> ObjectList;
ObjectList m_excess;
int m_lastExcess;
pthread_mutex_t m_excessMutex;
void pushExcess(T *);
void clearExcess(int);
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_lastExcess(0),
m_claimed(0),
m_scavenged(0)
{
pthread_mutex_init(&m_excessMutex, NULL);
}
template <typename T>
Scavenger<T>::~Scavenger()
{
if (m_scavenged < m_claimed) {
for (size_t i = 0; i < m_objects.size(); ++i) {
ObjectTimePair &pair = m_objects[i];
if (pair.first != 0) {
T *ot = pair.first;
pair.first = 0;
delete ot;
++m_scavenged;
}
}
}
clearExcess(0);
pthread_mutex_destroy(&m_excessMutex);
}
template <typename T>
void
Scavenger<T>::claim(T *t)
{
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;
}
}
std::cerr << "WARNING: Scavenger::claim(" << t << "): run out of slots, "
<< "using non-RT-safe method" << std::endl;
pushExcess(t);
}
template <typename T>
void
Scavenger<T>::scavenge()
{
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 (pair.first != 0 && pair.second + m_sec < sec) {
T *ot = pair.first;
pair.first = 0;
delete ot;
++m_scavenged;
}
}
if (sec > m_lastExcess + m_sec) {
clearExcess(sec);
}
}
template <typename T>
void
Scavenger<T>::pushExcess(T *t)
{
pthread_mutex_lock(&m_excessMutex);
m_excess.push_back(t);
struct timeval tv;
(void)gettimeofday(&tv, 0);
m_lastExcess = tv.tv_sec;
pthread_mutex_unlock(&m_excessMutex);
}
template <typename T>
void
Scavenger<T>::clearExcess(int sec)
{
pthread_mutex_lock(&m_excessMutex);
for (typename ObjectList::iterator i = m_excess.begin();
i != m_excess.end(); ++i) {
delete *i;
}
m_excess.clear();
m_lastExcess = sec;
pthread_mutex_unlock(&m_excessMutex);
}
}
#endif
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