org.apache.cassandra.io.util.WrappingRebufferer Maven / Gradle / Ivy
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the 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.
*/
package org.apache.cassandra.io.util;
import java.nio.ByteBuffer;
import javax.annotation.concurrent.NotThreadSafe;
/**
* Instantiated once per RandomAccessReader, thread-unsafe.
* The instances reuse themselves as the BufferHolder to avoid having to return a new object for each rebuffer call.
* Only one buffer holder can be active at a time. Calling {@link #rebuffer(long)} before the previously obtained
* buffer holder is released will throw {@link AssertionError}. We will get that exception also in case we try to close
* the rebufferer without closing the recently obtained buffer holder.
*
* Calling methods of {@link BufferHolder} will also produce {@link AssertionError} if buffer holder is not acquired.
*
* The overriding classes must conform to the aforementioned rules.
*/
@NotThreadSafe
public abstract class WrappingRebufferer implements Rebufferer, Rebufferer.BufferHolder
{
protected final Rebufferer wrapped;
protected BufferHolder bufferHolder;
protected ByteBuffer buffer;
protected long offset;
public WrappingRebufferer(Rebufferer wrapped)
{
this.wrapped = wrapped;
}
@Override
public BufferHolder rebuffer(long position)
{
assert buffer == null;
bufferHolder = wrapped.rebuffer(position);
buffer = bufferHolder.buffer();
offset = bufferHolder.offset();
return this;
}
@Override
public ChannelProxy channel()
{
return wrapped.channel();
}
@Override
public long fileLength()
{
return wrapped.fileLength();
}
@Override
public double getCrcCheckChance()
{
return wrapped.getCrcCheckChance();
}
@Override
public void close()
{
assert buffer == null : "Rebufferer is attempted to be closed but the buffer holder has not been released";
wrapped.close();
}
@Override
public void closeReader()
{
wrapped.closeReader();
}
@Override
public String toString()
{
return String.format("%s[]:%s", getClass().getSimpleName(), wrapped.toString());
}
@Override
public ByteBuffer buffer()
{
assert buffer != null : "Buffer holder has not been acquired";
return buffer;
}
@Override
public long offset()
{
assert buffer != null : "Buffer holder has not been acquired";
return offset;
}
@Override
public void release()
{
assert buffer != null;
if (bufferHolder != null)
{
bufferHolder.release();
bufferHolder = null;
}
buffer = null;
}
}