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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.jdisc;

/**
 * Utility class for working with reference-counted {@link SharedResource}s.
 *
 * Sometimes, you may want a method to return both a resource object and
 * a {@link ResourceReference} that refers the resource object (for later release of the resource).
 * Java methods cannot return multiple objects, so this class provides Pair-like functionality
 * for returning both.
 *
 * Example usage:
 *  *     ReferencedResource<MyResource> getResource() {
 *         final ResourceReference ref = resource.refer();
 *         return new ReferencedResource(resource, ref);
 *     }
 *
 *     void useResource() {
 *         final ReferencedResource<MyResource> referencedResource = getResource();
 *         referencedResource.getResource().use();
 *         referencedResource.getReference().close();
 *     }
 * 
 *
 * This class implements AutoCloseable, so the latter method may also be written as follows:
 *  *     void useResource() {
 *         for (final ReferencedResource<MyResource> referencedResource = getResource()) {
 *             referencedResource.getResource().use();
 *         }
 *     }
 * 
 *
 * @author bakksjo
 */
public class ReferencedResource implements AutoCloseable {
    private final T resource;
    private final ResourceReference reference;

    public ReferencedResource(final T resource, final ResourceReference reference) {
        this.resource = resource;
        this.reference = reference;
    }

    public T getResource() {
        return resource;
    }

    public ResourceReference getReference() {
        return reference;
    }

    @Override
    public void close() {
        reference.close();
    }
}