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comparison dwtx/jface/resource/AbstractResourceManager.d @ 9:6c14e54dfc11

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completed /jface/resource/
author Frank Benoit <benoit@tionex.de>
date Sat, 29 Mar 2008 02:25:12 +0100
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8:a3ff22a98bef 9:6c14e54dfc11
1 /*******************************************************************************
2 * Copyright (c) 2004, 2006 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM Corporation - initial API and implementation
10 * Port to the D programming language:
11 * Frank Benoit <benoit@tionex.de>
12 *******************************************************************************/
13 module dwtx.jface.resource.AbstractResourceManager;
14
15 import dwtx.jface.resource.ResourceManager;
16 import dwtx.jface.resource.DeviceResourceDescriptor;
17
18 import tango.util.collection.HashMap;
19 import tango.util.collection.model.Map;
20
21 import dwt.dwthelper.utils;
22
23 /**
24 * Abstract implementation of ResourceManager. Maintains reference counts for all previously
25 * allocated DWT resources. Delegates to the abstract method allocate(...) the first time a resource
26 * is referenced and delegates to the abstract method deallocate(...) the last time a reference is
27 * removed.
28 *
29 * @since 3.1
30 */
31 abstract class AbstractResourceManager : ResourceManager {
32
33 /**
34 * Map of ResourceDescriptor onto RefCount. (null when empty)
35 */
36 private HashMap!(DeviceResourceDescriptor,RefCount) map = null;
37
38 /**
39 * Holds a reference count for a previously-allocated resource
40 */
41 private static class RefCount {
42 Object resource;
43 int count = 1;
44
45 this(Object resource) {
46 this.resource = resource;
47 }
48 }
49
50 /**
51 * Called the first time a resource is requested. Should allocate and return a resource
52 * of the correct type.
53 *
54 * @since 3.1
55 *
56 * @param descriptor identifier for the resource to allocate
57 * @return the newly allocated resource
58 * @throws DeviceResourceException Thrown when allocation of an DWT device resource fails
59 */
60 protected abstract Object allocate(DeviceResourceDescriptor descriptor);
61
62 /**
63 * Called the last time a resource is dereferenced. Should release any resources reserved by
64 * allocate(...).
65 *
66 * @since 3.1
67 *
68 * @param resource resource being deallocated
69 * @param descriptor identifier for the resource
70 */
71 protected abstract void deallocate(Object resource, DeviceResourceDescriptor descriptor);
72
73 /* (non-Javadoc)
74 * @see ResourceManager#create(DeviceResourceDescriptor)
75 */
76 public final Object create(DeviceResourceDescriptor descriptor){
77
78 // Lazily allocate the map
79 if (map is null) {
80 map = new HashMap!(DeviceResourceDescriptor,RefCount);
81 }
82
83 // Get the current reference count
84 RefCount count = map.get(descriptor);
85 if (count !is null) {
86 // If this resource already exists, increment the reference count and return
87 // the existing resource.
88 count.count++;
89 return count.resource;
90 }
91
92 // Allocate and return a new resource (with ref count = 1)
93 Object resource = allocate(descriptor);
94
95 count = new RefCount(resource);
96 map.add(descriptor, count);
97
98 return resource;
99 }
100
101 /* (non-Javadoc)
102 * @see ResourceManager#destroy(DeviceResourceDescriptor)
103 */
104 public final void destroy(DeviceResourceDescriptor descriptor) {
105 // If the map is empty (null) then there are no resources to dispose
106 if (map is null) {
107 return;
108 }
109
110 // Find the existing resource
111 RefCount count = map.get(descriptor);
112 if (count !is null) {
113 // If the resource exists, decrement the reference count.
114 count.count--;
115 if (count.count is 0) {
116 // If this was the last reference, deallocate it.
117 deallocate(count.resource, descriptor);
118 map.removeKey(descriptor);
119 }
120 }
121
122 // Null out the map when empty to save a small amount of memory
123 if (map.drained()) {
124 map = null;
125 }
126 }
127
128 /**
129 * Deallocates any resources allocated by this registry that have not yet been
130 * deallocated.
131 *
132 * @since 3.1
133 */
134 public void dispose() {
135 super.dispose();
136
137 if (map is null) {
138 return;
139 }
140
141 foreach( key, val; map ){
142 deallocate(val.resource, key);
143 }
144
145 map = null;
146 }
147
148 /* (non-Javadoc)
149 * @see dwtx.jface.resource.ResourceManager#find(dwtx.jface.resource.DeviceResourceDescriptor)
150 */
151 public Object find(DeviceResourceDescriptor descriptor) {
152 if (map is null) {
153 return null;
154 }
155 RefCount refCount = cast(RefCount)map.get(descriptor);
156 if (refCount is null)
157 return null;
158 return refCount.resource;
159 }
160 }