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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file, and Oracle licenses the original version of this file under the BSD

 * license:

 */

/*

   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")

   and the BSD License (the "BSD License"), with licensee being free to

   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache

   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the

   following notice applies to you:

       You may obtain a copy of the Apache 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.

   If you choose to use this file in compliance with the BSD License, the

   following notice applies to you:

       Redistribution and use in source and binary forms, with or without

       modification, are permitted provided that the following conditions are

       met:

       * Redistributions of source code must retain the above copyright

         notice, this list of conditions and the following disclaimer.

       * Redistributions in binary form must reproduce the above copyright

         notice, this list of conditions and the following disclaimer in the

         documentation and/or other materials provided with the distribution.

       * Neither the name of the copyright holder nor the names of

         contributors may be used to endorse or promote products derived from

         this software without specific prior written permission.

       THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS

       IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED

       TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A

       PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER

       BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

       CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

       SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR

       BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

       WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

       OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF

       ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

package jdk.dynalink.linker.support;

import java.util.LinkedList;

import java.util.List;

import java.util.Objects;

import jdk.dynalink.linker.GuardedInvocation;

import jdk.dynalink.linker.GuardingDynamicLinker;

import jdk.dynalink.linker.LinkRequest;

import jdk.dynalink.linker.LinkerServices;

/**

 * A {@link GuardingDynamicLinker} that delegates sequentially to a list of

 * other guarding dynamic linkers in its

 * {@link #getGuardedInvocation(LinkRequest, LinkerServices)}.

 */

public class CompositeGuardingDynamicLinker implements GuardingDynamicLinker {

    private final GuardingDynamicLinker[] linkers;

    /**

     * Creates a new composite linker.

     *

     * @param linkers a list of component linkers.

     * @throws NullPointerException if {@code linkers} or any of its elements

     * are null.

     */

    public CompositeGuardingDynamicLinker(final Iterable<? extends GuardingDynamicLinker> linkers) {

        final List<GuardingDynamicLinker> l = new LinkedList<>();

        for(final GuardingDynamicLinker linker: linkers) {

            l.add(Objects.requireNonNull(linker));

        }

        this.linkers = l.toArray(new GuardingDynamicLinker[0]);

    }

    /**

     * Delegates the call to its component linkers. The first non-null value

     * returned from a component linker is returned. If no component linker

     * returns a non-null invocation, null is returned.

     * @param linkRequest the object describing the request for linking a

     * particular invocation

     * @param linkerServices linker services

     * @return the first non-null return value from a component linker, or null

     * if none of the components returned a non-null.

     */

    @Override

    public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)

            throws Exception {

        for(final GuardingDynamicLinker linker: linkers) {

            final GuardedInvocation invocation = linker.getGuardedInvocation(linkRequest, linkerServices);

            if(invocation != null) {

                return invocation;

            }

        }

        return null;

    }

}