/*

 * Copyright (c) 2015, 2018, Oracle and/or its affiliates. All rights reserved.

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

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

import java.nio.ByteBuffer;

import java.util.concurrent.ConcurrentLinkedQueue;

/**

 * The class provides reuse of ByteBuffers.

 * It is supposed that all requested buffers have the same size for a long period of time.

 * That is why there is no any logic splitting buffers into different buckets (by size). It's unnecessary.

 *

 * At the same moment it is allowed to change requested buffers size (all smaller buffers will be discarded).

 * It may be needed for example, if after rehandshaking netPacketBufferSize was changed.

 */

public class ByteBufferPool {

    private final java.util.Queue<ByteBuffer> pool = new ConcurrentLinkedQueue<>();

    public ByteBufferPool() {

    }

    public ByteBufferReference get(int size) {

        ByteBuffer buffer;

        while ((buffer = pool.poll()) != null) {

            if (buffer.capacity() >= size) {

                return ByteBufferReference.of(buffer, this);

            }

        }

        return ByteBufferReference.of(ByteBuffer.allocate(size), this);

    }

    public void release(ByteBuffer buffer) {

        buffer.clear();

        pool.offer(buffer);

    }

}