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1 /*******************************************************************************
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2 * Copyright (c) 2004, 2006 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.resource.AbstractResourceManager;
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14
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15 import dwtx.jface.resource.ResourceManager;
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16 import dwtx.jface.resource.DeviceResourceDescriptor;
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17
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18 import tango.util.collection.HashMap;
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19 import tango.util.collection.model.Map;
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20
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21 import dwt.dwthelper.utils;
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22
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23 /**
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24 * Abstract implementation of ResourceManager. Maintains reference counts for all previously
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25 * allocated DWT resources. Delegates to the abstract method allocate(...) the first time a resource
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26 * is referenced and delegates to the abstract method deallocate(...) the last time a reference is
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27 * removed.
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28 *
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29 * @since 3.1
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30 */
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31 abstract class AbstractResourceManager : ResourceManager {
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32
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33 /**
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34 * Map of ResourceDescriptor onto RefCount. (null when empty)
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35 */
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36 private HashMap!(DeviceResourceDescriptor,RefCount) map = null;
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37
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38 /**
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39 * Holds a reference count for a previously-allocated resource
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40 */
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41 private static class RefCount {
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42 Object resource;
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43 int count = 1;
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44
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45 this(Object resource) {
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46 this.resource = resource;
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47 }
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48 }
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49
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50 /**
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51 * Called the first time a resource is requested. Should allocate and return a resource
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52 * of the correct type.
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53 *
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54 * @since 3.1
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55 *
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56 * @param descriptor identifier for the resource to allocate
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57 * @return the newly allocated resource
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58 * @throws DeviceResourceException Thrown when allocation of an DWT device resource fails
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59 */
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60 protected abstract Object allocate(DeviceResourceDescriptor descriptor);
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61
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62 /**
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63 * Called the last time a resource is dereferenced. Should release any resources reserved by
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64 * allocate(...).
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65 *
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66 * @since 3.1
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67 *
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68 * @param resource resource being deallocated
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69 * @param descriptor identifier for the resource
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70 */
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71 protected abstract void deallocate(Object resource, DeviceResourceDescriptor descriptor);
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72
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73 /* (non-Javadoc)
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74 * @see ResourceManager#create(DeviceResourceDescriptor)
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75 */
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76 public final Object create(DeviceResourceDescriptor descriptor){
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77
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78 // Lazily allocate the map
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79 if (map is null) {
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80 map = new HashMap!(DeviceResourceDescriptor,RefCount);
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81 }
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82
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83 // Get the current reference count
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84 RefCount count = map.get(descriptor);
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85 if (count !is null) {
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86 // If this resource already exists, increment the reference count and return
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87 // the existing resource.
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88 count.count++;
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89 return count.resource;
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90 }
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91
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92 // Allocate and return a new resource (with ref count = 1)
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93 Object resource = allocate(descriptor);
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94
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95 count = new RefCount(resource);
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96 map.add(descriptor, count);
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97
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98 return resource;
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99 }
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100
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101 /* (non-Javadoc)
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102 * @see ResourceManager#destroy(DeviceResourceDescriptor)
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103 */
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104 public final void destroy(DeviceResourceDescriptor descriptor) {
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105 // If the map is empty (null) then there are no resources to dispose
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106 if (map is null) {
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107 return;
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108 }
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109
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110 // Find the existing resource
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111 RefCount count = map.get(descriptor);
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112 if (count !is null) {
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113 // If the resource exists, decrement the reference count.
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114 count.count--;
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115 if (count.count is 0) {
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116 // If this was the last reference, deallocate it.
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117 deallocate(count.resource, descriptor);
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118 map.removeKey(descriptor);
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119 }
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120 }
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121
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122 // Null out the map when empty to save a small amount of memory
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123 if (map.drained()) {
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124 map = null;
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125 }
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126 }
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127
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128 /**
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129 * Deallocates any resources allocated by this registry that have not yet been
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130 * deallocated.
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131 *
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132 * @since 3.1
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133 */
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134 public void dispose() {
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135 super.dispose();
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136
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137 if (map is null) {
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138 return;
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139 }
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140
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141 foreach( key, val; map ){
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142 deallocate(val.resource, key);
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143 }
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144
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145 map = null;
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146 }
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147
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148 /* (non-Javadoc)
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149 * @see dwtx.jface.resource.ResourceManager#find(dwtx.jface.resource.DeviceResourceDescriptor)
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150 */
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151 public Object find(DeviceResourceDescriptor descriptor) {
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152 if (map is null) {
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153 return null;
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154 }
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155 RefCount refCount = cast(RefCount)map.get(descriptor);
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156 if (refCount is null)
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157 return null;
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158 return refCount.resource;
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159 }
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160 }
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