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1 /*******************************************************************************
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2 * Copyright (c) 2004, 2005 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwtx.jface.viewers.deferred.ChangeQueue;
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14
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15 import tango.util.collection.LinkSeq;
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16
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17 import dwt.dwthelper.utils;
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18
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19 /**
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20 * Holds a queue of additions, removals, updates, and SET calls for a
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21 * BackgroundContentProvider
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22 */
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23 final class ChangeQueue {
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24 /**
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25 * Represents the addition of an item
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26 * @since 3.1
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27 */
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28 public static const int ADD = 0;
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29 /**
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30 * Represents the removal of an item
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31 * @since 3.1
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32 */
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33 public static const int REMOVE = 1;
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34 /**
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35 * Represents a reset of all the items
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36 * @since 3.1
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37 */
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38 public static const int SET = 2;
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39 /**
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40 * Represents an update of an item
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41 * @since 3.1
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42 */
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43 public static const int UPDATE = 3;
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44
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45 /**
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46 *
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47 * @since 3.1
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48 */
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49 public static final class Change {
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50 private int type;
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51 private Object[] elements;
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52
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53 /**
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54 * Create a change of the specified type that affects the given elements.
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55 *
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56 * @param type one of <code>ADD</code>, <code>REMOVE</code>, <code>SET</code>, or <code>UPDATE</code>.
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57 * @param elements the elements affected by the change.
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58 *
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59 * @since 3.1
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60 */
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61 public this(int type, Object[] elements) {
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62 this.type = type;
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63 this.elements = elements;
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64 }
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65
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66 /**
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67 * Get the type of change.
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68 * @return one of <code>ADD</code>, <code>REMOVE</code>, <code>SET</code>, or <code>UPDATE</code>.
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69 *
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70 * @since 3.1
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71 */
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72 public int getType() {
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73 return type;
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74 }
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75
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76 /**
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77 * Return the elements associated with the change.
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78 * @return the elements affected by the change.
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79 *
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80 * @since 3.1
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81 */
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82 public Object[] getElements() {
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83 return elements;
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84 }
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85 }
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86
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87 private LinkSeq!(Change) queue;
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88 private int workload = 0;
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89
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90 public this(){
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91 queue = new LinkSeq!(Change);
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92 }
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93
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94 /**
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95 * Create a change of the given type and elements and enqueue it.
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96 *
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97 * @param type the type of change to be created
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98 * @param elements the elements affected by the change
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99 */
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100 public synchronized void enqueue(int type, Object[] elements) {
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101 enqueue(new Change(type, elements));
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102 }
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103
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104 /**
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105 * Add the specified change to the queue
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106 * @param toQueue the change to be added
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107 */
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108 public synchronized void enqueue(Change toQueue) {
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109 // A SET event makes all previous adds, removes, and sets redundant... so remove
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110 // them from the queue
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111 if (toQueue.type is SET) {
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112 workload = 0;
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113 LinkSeq!(Change) newQueue = new LinkSeq!(Change);
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114 foreach( next; queue ){
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115
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116 if (next.getType() is ADD || next.getType() is REMOVE || next.getType() is SET) {
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117 continue;
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118 }
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119
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120 newQueue.append(next);
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121 workload += next.elements.length;
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122 }
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123 queue = newQueue;
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124 }
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125
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126 queue.append(toQueue);
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127 workload += toQueue.elements.length;
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128 }
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129
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130 /**
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131 * Remove the first change from the queue.
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132 * @return the first change
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133 */
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134 public synchronized Change dequeue() {
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135 Change result = queue.head;
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136 queue.removeHead();
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137
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138 workload -= result.elements.length;
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139 return result;
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140 }
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141
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142 /**
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143 * Return whether the queue is empty
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144 * @return <code>true</code> if empty, <code>false</code> otherwise
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145 */
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146 public synchronized bool isEmpty() {
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147 return queue.drained();
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148 }
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149 }
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