Mercurial > projects > dwt-addons
view dwtx/jface/resource/AbstractResourceManager.d @ 9:6c14e54dfc11
completed /jface/resource/
author | Frank Benoit <benoit@tionex.de> |
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date | Sat, 29 Mar 2008 02:25:12 +0100 |
parents | |
children | da5ad8eedf5d |
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/******************************************************************************* * Copyright (c) 2004, 2006 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * IBM Corporation - initial API and implementation * Port to the D programming language: * Frank Benoit <benoit@tionex.de> *******************************************************************************/ module dwtx.jface.resource.AbstractResourceManager; import dwtx.jface.resource.ResourceManager; import dwtx.jface.resource.DeviceResourceDescriptor; import tango.util.collection.HashMap; import tango.util.collection.model.Map; import dwt.dwthelper.utils; /** * Abstract implementation of ResourceManager. Maintains reference counts for all previously * allocated DWT resources. Delegates to the abstract method allocate(...) the first time a resource * is referenced and delegates to the abstract method deallocate(...) the last time a reference is * removed. * * @since 3.1 */ abstract class AbstractResourceManager : ResourceManager { /** * Map of ResourceDescriptor onto RefCount. (null when empty) */ private HashMap!(DeviceResourceDescriptor,RefCount) map = null; /** * Holds a reference count for a previously-allocated resource */ private static class RefCount { Object resource; int count = 1; this(Object resource) { this.resource = resource; } } /** * Called the first time a resource is requested. Should allocate and return a resource * of the correct type. * * @since 3.1 * * @param descriptor identifier for the resource to allocate * @return the newly allocated resource * @throws DeviceResourceException Thrown when allocation of an DWT device resource fails */ protected abstract Object allocate(DeviceResourceDescriptor descriptor); /** * Called the last time a resource is dereferenced. Should release any resources reserved by * allocate(...). * * @since 3.1 * * @param resource resource being deallocated * @param descriptor identifier for the resource */ protected abstract void deallocate(Object resource, DeviceResourceDescriptor descriptor); /* (non-Javadoc) * @see ResourceManager#create(DeviceResourceDescriptor) */ public final Object create(DeviceResourceDescriptor descriptor){ // Lazily allocate the map if (map is null) { map = new HashMap!(DeviceResourceDescriptor,RefCount); } // Get the current reference count RefCount count = map.get(descriptor); if (count !is null) { // If this resource already exists, increment the reference count and return // the existing resource. count.count++; return count.resource; } // Allocate and return a new resource (with ref count = 1) Object resource = allocate(descriptor); count = new RefCount(resource); map.add(descriptor, count); return resource; } /* (non-Javadoc) * @see ResourceManager#destroy(DeviceResourceDescriptor) */ public final void destroy(DeviceResourceDescriptor descriptor) { // If the map is empty (null) then there are no resources to dispose if (map is null) { return; } // Find the existing resource RefCount count = map.get(descriptor); if (count !is null) { // If the resource exists, decrement the reference count. count.count--; if (count.count is 0) { // If this was the last reference, deallocate it. deallocate(count.resource, descriptor); map.removeKey(descriptor); } } // Null out the map when empty to save a small amount of memory if (map.drained()) { map = null; } } /** * Deallocates any resources allocated by this registry that have not yet been * deallocated. * * @since 3.1 */ public void dispose() { super.dispose(); if (map is null) { return; } foreach( key, val; map ){ deallocate(val.resource, key); } map = null; } /* (non-Javadoc) * @see dwtx.jface.resource.ResourceManager#find(dwtx.jface.resource.DeviceResourceDescriptor) */ public Object find(DeviceResourceDescriptor descriptor) { if (map is null) { return null; } RefCount refCount = cast(RefCount)map.get(descriptor); if (refCount is null) return null; return refCount.resource; } }