/*
 * Copyright (c) 2011, 2014, 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
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package com.sun.webkit.network;

import java.nio.ByteBuffer;
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.Semaphore;

A pool of byte buffers that can be shared by multiple concurrent
clients.
/**
 * A pool of byte buffers that can be shared by multiple concurrent
 * clients.
 */
final class ByteBufferPool {

    
The shared collection of byte buffers.
/**
     * The shared collection of byte buffers.
     */
    private final Queue<ByteBuffer> byteBuffers =
            new ConcurrentLinkedQueue<ByteBuffer>();

    
The size of each byte buffer.
/**
     * The size of each byte buffer.
     */
    private final int bufferSize;


    
Creates a new pool.
/**
     * Creates a new pool.
     */
    private ByteBufferPool(int bufferSize) {
        this.bufferSize = bufferSize;
    }


    
Creates a new pool.
/**
     * Creates a new pool.
     */
    static ByteBufferPool newInstance(int bufferSize) {
        return new ByteBufferPool(bufferSize);
    }

    
Creates a new allocator associated with this pool. The allocator will allow its client to allocate and release buffers and will ensure that there are no more than maxBufferCount buffers allocated through this allocator at any given time moment. /**
     * Creates a new allocator associated with this pool.
     * The allocator will allow its client to allocate and release
     * buffers and will ensure that there are no more than
     * {@code maxBufferCount} buffers allocated through this allocator
     * at any given time moment.
     */
    ByteBufferAllocator newAllocator(int maxBufferCount) {
        return new ByteBufferAllocatorImpl(maxBufferCount);
    }

    
The allocator implementation.
/**
     * The allocator implementation.
     */
    private final class ByteBufferAllocatorImpl implements ByteBufferAllocator {

        
The semaphore used to limit the number of buffers
allocated through this allocator.
/**
         * The semaphore used to limit the number of buffers
         * allocated through this allocator.
         */
        private final Semaphore semaphore;


        
Creates a new allocator.
/**
         * Creates a new allocator.
         */
        private ByteBufferAllocatorImpl(int maxBufferCount) {
            semaphore = new Semaphore(maxBufferCount);
        }


        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public ByteBuffer allocate() throws InterruptedException {
            semaphore.acquire();
            ByteBuffer byteBuffer = byteBuffers.poll();
            if (byteBuffer == null) {
                byteBuffer = ByteBuffer.allocateDirect(bufferSize);
            }
            return byteBuffer;
        }

        
{@inheritDoc}
/**
         * {@inheritDoc}
         */
        @Override
        public void release(ByteBuffer byteBuffer) {
            byteBuffers.add(byteBuffer);
            semaphore.release();
        }
    }
}

An object that can allocate and release byte buffers.
/**
 * An object that can allocate and release byte buffers.
 */
interface ByteBufferAllocator {

    
Allocates a byte buffer.
/**
     * Allocates a byte buffer.
     */
    ByteBuffer allocate() throws InterruptedException;

    
Releases a byte buffer.
/**
     * Releases a byte buffer.
     */
    void release(ByteBuffer byteBuffer);
}