--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/platform35/org.eclipse.core.resources/src/org/eclipse/core/internal/resources/mapping/ModelProviderManager.java	Thu Jul 30 11:56:23 2009 -0500
@@ -0,0 +1,76 @@
+/*******************************************************************************
+ * Copyright (c) 2005, 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
+ *******************************************************************************/
+package org.eclipse.core.internal.resources.mapping;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.eclipse.core.internal.utils.Policy;
+import org.eclipse.core.resources.ResourcesPlugin;
+import org.eclipse.core.resources.mapping.IModelProviderDescriptor;
+import org.eclipse.core.resources.mapping.ModelProvider;
+import org.eclipse.core.runtime.*;
+
+public class ModelProviderManager {
+
+	private static Map descriptors;
+	private static ModelProviderManager instance;
+
+	public synchronized static ModelProviderManager getDefault() {
+		if (instance == null) {
+			instance = new ModelProviderManager();
+		}
+		return instance;
+	}
+
+	private void detectCycles() {
+		// TODO Auto-generated method stub
+
+	}
+
+	public IModelProviderDescriptor getDescriptor(String id) {
+		lazyInitialize();
+		return (IModelProviderDescriptor) descriptors.get(id);
+	}
+
+	public IModelProviderDescriptor[] getDescriptors() {
+		lazyInitialize();
+		return (IModelProviderDescriptor[]) descriptors.values().toArray(new IModelProviderDescriptor[descriptors.size()]);
+	}
+
+	public ModelProvider getModelProvider(String modelProviderId) throws CoreException {
+		IModelProviderDescriptor desc = getDescriptor(modelProviderId);
+		if (desc == null)
+			return null;
+		return desc.getModelProvider();
+	}
+
+	protected void lazyInitialize() {
+		if (descriptors != null)
+			return;
+		IExtensionPoint point = Platform.getExtensionRegistry().getExtensionPoint(ResourcesPlugin.PI_RESOURCES, ResourcesPlugin.PT_MODEL_PROVIDERS);
+		IExtension[] extensions = point.getExtensions();
+		descriptors = new HashMap(extensions.length * 2 + 1);
+		for (int i = 0, imax = extensions.length; i < imax; i++) {
+			IModelProviderDescriptor desc = null;
+			try {
+				desc = new ModelProviderDescriptor(extensions[i]);
+			} catch (CoreException e) {
+				Policy.log(e);
+			}
+			if (desc != null)
+				descriptors.put(desc.getId(), desc);
+		}
+		//do cycle detection now so it only has to be done once
+		//cycle detection on a graph subset is a pain
+		detectCycles();
+	}
+
+}