/*
 * Copyright (c) 2015, 2017, 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.
 *
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package jdk.incubator.http.internal.common;

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.
/**
 * 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);
    }

}