org.eclipse.xtext.scoping.impl.MapBasedScope.java Source code

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Here is the source code for org.eclipse.xtext.scoping.impl.MapBasedScope.java

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/*******************************************************************************
 * Copyright (c) 2010 itemis AG (http://www.itemis.eu) 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
 *******************************************************************************/
package org.eclipse.xtext.scoping.impl;

import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.Map;

import org.eclipse.xtext.naming.QualifiedName;
import org.eclipse.xtext.resource.IEObjectDescription;
import org.eclipse.xtext.scoping.IScope;

import com.google.common.collect.Iterables;

/**
 * A scope implemented using a {@link Map} used for efficient lookup of ordinary named 
 * {@link org.eclipse.xtext.resource.EObjectDescription EObjectDescriptions}. 
 * 
 * This implementation assumes, that the keys of the {@link Map} correspond to the keys of the contained {@link org.eclipse.xtext.resource.EObjectDescription}.
 * Additionally it assumes, that those keys are equal to <code>description.getName().toLowerCase()</code>.
 * 
 * When looking up elements using {@link #getElements(QualifiedName)} this implementation looks up the the elements from the map, hence are much 
 * more efficient for many {@link IEObjectDescription}s.  
 * 
 * @author Sven Efftinge - Initial contribution and API
 * @author Sebastian Zarnekow
 */
public class MapBasedScope extends AbstractScope {

    public static IScope createScope(IScope parent, Iterable<IEObjectDescription> descriptions,
            boolean ignoreCase) {
        Map<QualifiedName, IEObjectDescription> map = null;
        for (IEObjectDescription description : descriptions) {
            if (map == null)
                map = new LinkedHashMap<QualifiedName, IEObjectDescription>(4);
            QualifiedName name = ignoreCase ? description.getName().toLowerCase() : description.getName();
            IEObjectDescription previous = map.put(name, description);
            // we are optimistic that no duplicate names are used
            // however, if the name was already used, the first one should win
            if (previous != null) {
                map.put(name, previous);
            }
        }
        if (map == null || map.isEmpty()) {
            return parent;
        }
        return new MapBasedScope(parent, map, ignoreCase);
    }

    /**
     * @since 2.3
     */
    public static IScope createScope(IScope parent, Collection<IEObjectDescription> descriptions) {
        if (descriptions.size() == 1) {
            IEObjectDescription description = Iterables.getOnlyElement(descriptions);
            return new MapBasedScope(parent, Collections.singletonMap(description.getName(), description), false);
        } else if (descriptions.isEmpty()) {
            return parent;
        }
        return createScope(parent, descriptions, false);
    }

    public static IScope createScope(IScope parent, Iterable<IEObjectDescription> descriptions) {
        return createScope(parent, descriptions, false);
    }

    private Map<QualifiedName, IEObjectDescription> elements;

    protected MapBasedScope(IScope parent, Map<QualifiedName, IEObjectDescription> elements, boolean ignoreCase) {
        super(parent, ignoreCase);
        this.elements = elements;
    }

    @Override
    protected Iterable<IEObjectDescription> getAllLocalElements() {
        return elements.values();
    }

    @Override
    protected Iterable<IEObjectDescription> getLocalElementsByName(QualifiedName name) {
        IEObjectDescription result = null;
        if (isIgnoreCase()) {
            result = elements.get(name.toLowerCase());
        } else {
            result = elements.get(name);
        }
        if (result == null)
            return Collections.emptyList();
        return Collections.singleton(result);
    }

    @Override
    protected boolean isShadowed(IEObjectDescription fromParent) {
        if (isIgnoreCase()) {
            boolean result = elements.containsKey(fromParent.getName().toLowerCase());
            return result;
        } else {
            boolean result = elements.containsKey(fromParent.getName());
            return result;
        }
    }
}