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1 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
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2
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3 /*
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4 Sonic Visualiser
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5 An audio file viewer and annotation editor.
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6 Centre for Digital Music, Queen Mary, University of London.
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7 This file copyright 2006 Chris Cannam.
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8
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9 This program is free software; you can redistribute it and/or
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10 modify it under the terms of the GNU General Public License as
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11 published by the Free Software Foundation; either version 2 of the
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12 License, or (at your option) any later version. See the file
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13 COPYING included with this distribution for more information.
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14 */
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15
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16 /*
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17 This is a modified version of a source file from the
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18 Rosegarden MIDI and audio sequencer and notation editor.
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19 This file copyright 2000-2006 Chris Cannam.
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20 */
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21
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22 #ifndef _SCAVENGER_H_
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23 #define _SCAVENGER_H_
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24
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25 #include "System.h"
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26
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27 #include <vector>
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28 #include <sys/time.h>
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29
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30 /**
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31 * A very simple class that facilitates running things like plugins
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32 * without locking, by collecting unwanted objects and deleting them
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33 * after a delay so as to be sure nobody's in the middle of using
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34 * them. Requires scavenge() to be called regularly from a non-RT
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35 * thread.
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36 *
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37 * This is currently not at all suitable for large numbers of objects
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38 * -- it's just a quick hack for use with things like plugins.
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39 */
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40
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41 template <typename T>
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42 class Scavenger
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43 {
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44 public:
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45 Scavenger(int sec = 2, int defaultObjectListSize = 200);
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46
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47 /**
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48 * Call from an RT thread etc., to pass ownership of t to us.
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49 * Only one thread should be calling this on any given scavenger.
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50 */
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51 void claim(T *t);
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52
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53 /**
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54 * Call from a non-RT thread.
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55 * Only one thread should be calling this on any given scavenger.
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56 */
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57 void scavenge(bool clearNow = false);
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58
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59 protected:
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60 typedef std::pair<T *, int> ObjectTimePair;
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61 typedef std::vector<ObjectTimePair> ObjectTimeList;
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62 ObjectTimeList m_objects;
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63 int m_sec;
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64
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65 unsigned int m_claimed;
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66 unsigned int m_scavenged;
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67 };
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68
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69 /**
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70 * A wrapper to permit arrays to be scavenged.
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71 */
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72
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73 template <typename T>
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74 class ScavengerArrayWrapper
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75 {
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76 public:
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77 ScavengerArrayWrapper(T *array) : m_array(array) { }
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78 ~ScavengerArrayWrapper() { delete[] m_array; }
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79
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80 private:
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81 T *m_array;
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82 };
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83
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84
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85 template <typename T>
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86 Scavenger<T>::Scavenger(int sec, int defaultObjectListSize) :
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87 m_objects(ObjectTimeList(defaultObjectListSize)),
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88 m_sec(sec),
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89 m_claimed(0),
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90 m_scavenged(0)
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91 {
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92 }
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93
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94 template <typename T>
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95 void
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96 Scavenger<T>::claim(T *t)
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97 {
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98 // std::cerr << "Scavenger::claim(" << t << ")" << std::endl;
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99
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100 struct timeval tv;
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101 (void)gettimeofday(&tv, 0);
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102 int sec = tv.tv_sec;
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103
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104 for (size_t i = 0; i < m_objects.size(); ++i) {
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105 ObjectTimePair &pair = m_objects[i];
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106 if (pair.first == 0) {
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107 pair.second = sec;
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108 pair.first = t;
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109 ++m_claimed;
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110 return;
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111 }
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112 }
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113
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114 // Oh no -- run out of slots! Warn and discard something at
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115 // random (without deleting it -- it's probably safer to leak).
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116
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117 for (size_t i = 0; i < m_objects.size(); ++i) {
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118 ObjectTimePair &pair = m_objects[i];
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119 if (pair.first != 0) {
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120 pair.second = sec;
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121 pair.first = t;
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122 ++m_claimed;
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123 ++m_scavenged;
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124 }
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125 }
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126 }
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127
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128 template <typename T>
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129 void
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130 Scavenger<T>::scavenge(bool clearNow)
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131 {
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132 // std::cerr << "Scavenger::scavenge: scavenged " << m_scavenged << ", claimed " << m_claimed << std::endl;
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133
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134 if (m_scavenged >= m_claimed) return;
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135
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136 struct timeval tv;
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137 (void)gettimeofday(&tv, 0);
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138 int sec = tv.tv_sec;
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139
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140 for (size_t i = 0; i < m_objects.size(); ++i) {
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141 ObjectTimePair &pair = m_objects[i];
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142 if (clearNow ||
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143 (pair.first != 0 && pair.second + m_sec < sec)) {
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144 T *ot = pair.first;
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145 pair.first = 0;
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146 delete ot;
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147 ++m_scavenged;
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148 }
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149 }
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150 }
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151
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152 #endif
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