comparison base/Scavenger.h @ 0:da6937383da8

initial import

+/* -*- c-basic-offset: 4 -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    A waveform viewer and audio annotation editor.
+    Chris Cannam, Queen Mary University of London, 2005
+    
+    This is experimental software.  Not for distribution.
+*/
+
+/*
+   This is a modified version of a source file from the 
+   Rosegarden MIDI and audio sequencer and notation editor.
+   This file copyright 2000-2005 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();
+
+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()
+{
+//    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 (pair.first != 0 && pair.second + m_sec < sec) {
+	    T *ot = pair.first;
+	    pair.first = 0;
+	    delete ot;
+	    ++m_scavenged;
+	}
+    }
+}
+
+#endif