SingleOwnerByteBuffer.java

SingleOwnerByteBuffer.java

import java.nio.ByteBuffer;
import java.util.concurrent.locks.ReentrantLock;

public class SingleOwnerByteBuffer
{
    final ReentrantLock lock = new ReentrantLock();

    ByteBuffer bb;
    boolean disposed;

    public SingleOwnerByteBuffer(ByteBuffer bb)
    {
        this.bb = bb;
    }

    public int length()
    {
        assertOwnedByCurrentThread();

        return bb.remaining();
    }
    public byte get(int index)
    {
        assertOwnedByCurrentThread();

        return bb.get(index);
    }

    public void dispose()
    {
        lock.lock();
        try
        {
            if(disposed)
                return;

            /* unmap or dealloc bb here */

            disposed = true;
        }
        finally
        {
            lock.unlock();
        }
    }

    public void own()
    {
        lock.lock();

        if(disposed)
        {
            lock.unlock();
            throw new IllegalStateException("disposed");
        }
    }

    void assertOwnedByCurrentThread()
    {
        if(!lock.isHeldByCurrentThread())
            throw new IllegalStateException("not owned by current thread");
    }

    public void disown()
    {
        lock.unlock();
    }

    public static void main(String[] args) throws Exception
    {
        //test1(100_000, 1000_000);
        test2(100_000, 1000_000);
    }

    static public void test1(int cap, int repeat) throws Exception
    {
        int sum=0;
        long time = System.currentTimeMillis();
        ByteBuffer bb = ByteBuffer.allocateDirect(cap);
        for(int r=0; r<repeat; r++)
        {
            for(int i=0; i<cap; i++)
            {
                sum += bb.get(i);
            }
        }
        time = System.currentTimeMillis() - time;
        System.out.printf("time=%,d, sum=%,d %n", time, sum);
    }
    static public void test2(int cap, int repeat) throws Exception
    {
        int sum=0;
        long time = System.currentTimeMillis();
        ByteBuffer bb0 = ByteBuffer.allocateDirect(cap);
        SingleOwnerByteBuffer bb = new SingleOwnerByteBuffer(bb0);
        bb.own();
        for(int r=0; r<repeat; r++)
        {
            for(int i=0; i<cap; i++)
            {
                sum += bb.get(i);
            }
        }
        bb.disown();
        time = System.currentTimeMillis() - time;
        System.out.printf("time=%,d, sum=%,d %n", time, sum);
    }
}