SimplePermissionCollection.java

/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2016 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.wildfly.security.permission;

import java.security.Permission;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicReference;

import org.wildfly.security.util.ArrayIterator;

/**
 * A trivially simple permission collection, suitable as a default for most permission types (though probably not as efficient
 * as a specialized type in many cases).
 *
 * @author <a href="mailto:david.lloyd@redhat.com">David M. Lloyd</a>
 */
public final class SimplePermissionCollection extends AbstractPermissionCollection {

    private static final long serialVersionUID = - 9157630531211570679L;

    private final AtomicReference<Permission[]> permissionsRef = new AtomicReference<>(PermissionUtil.NO_PERMISSIONS);

    /**
     * Construct a new instance.
     *
     * @param sourcePermission the source permission for this collection (must not be {@code null})
     */
    public SimplePermissionCollection(final AbstractPermission<?> sourcePermission) {
        super(sourcePermission);
    }

    public int size() {
        return permissionsRef.get().length;
    }

    protected void doAdd(final AbstractPermission<?> permission) {
        Permission[] oldVal, readVal, newVal;
        int count;
        final AtomicReference<Permission[]> permissionsRef = this.permissionsRef;
        do {
            readVal = permissionsRef.get();
            do {
                count = 0;
                oldVal = readVal;
                for (Permission test : oldVal) {
                    if (test.implies(permission)) {
                        return;
                    }
                    if (! permission.implies(test)) {
                        // prepare to skip any permissions that are obviated by this one
                        count ++;
                    }
                }
                // see if it's still what we expect before we commit to the possibly expensive update...
                readVal = permissionsRef.get();
            } while (readVal != oldVal);
            newVal = new Permission[count + 1];
            int i = 0;
            for (Permission test : oldVal) {
                if (! permission.implies(test)) {
                    newVal[i++] = test;
                }
            }
            newVal[i] = permission;
        } while (! permissionsRef.compareAndSet(oldVal, newVal));
    }

    public boolean implies(final Permission permission) {
        for (Permission test : permissionsRef.get()) {
            if (test.implies(permission)) {
                return true;
            }
        }
        return false;
    }

    public Iterator<Permission> iterator() {
        return new ArrayIterator<Permission>(permissionsRef.get());
    }

    public Enumeration<Permission> elements() {
        return new ArrayIterator<Permission>(permissionsRef.get());
    }
}