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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.io.File;
import java.io.IOException;
import java.nio.ByteOrder;
import javax.annotation.concurrent.NotThreadSafe;
import com.google.common.primitives.Ints;
import org.apache.cassandra.io.compress.BufferType;
import org.apache.cassandra.io.util.Rebufferer.BufferHolder;
@NotThreadSafe
public class RandomAccessReader extends RebufferingInputStream implements FileDataInput
{
// The default buffer size when the client doesn't specify it
public static final int DEFAULT_BUFFER_SIZE = 4096;
// offset of the last file mark
private long markedPointer;
final Rebufferer rebufferer;
private BufferHolder bufferHolder = Rebufferer.EMPTY;
/**
* Only created through Builder
*
* @param rebufferer Rebufferer to use
*/
RandomAccessReader(Rebufferer rebufferer)
{
super(Rebufferer.EMPTY.buffer());
this.rebufferer = rebufferer;
}
/**
* Read data from file starting from current currentOffset to populate buffer.
*/
public void reBuffer()
{
if (isEOF())
return;
reBufferAt(current());
}
private void reBufferAt(long position)
{
bufferHolder.release();
bufferHolder = rebufferer.rebuffer(position);
buffer = bufferHolder.buffer();
buffer.position(Ints.checkedCast(position - bufferHolder.offset()));
assert buffer.order() == ByteOrder.BIG_ENDIAN : "Buffer must have BIG ENDIAN byte ordering";
}
@Override
public long getFilePointer()
{
if (buffer == null) // closed already
return rebufferer.fileLength();
return current();
}
protected long current()
{
return bufferHolder.offset() + buffer.position();
}
public String getPath()
{
return getChannel().filePath();
}
public ChannelProxy getChannel()
{
return rebufferer.channel();
}
@Override
public void reset() throws IOException
{
seek(markedPointer);
}
@Override
public boolean markSupported()
{
return true;
}
public long bytesPastMark()
{
long bytes = current() - markedPointer;
assert bytes >= 0;
return bytes;
}
public DataPosition mark()
{
markedPointer = current();
return new BufferedRandomAccessFileMark(markedPointer);
}
public void reset(DataPosition mark)
{
assert mark instanceof BufferedRandomAccessFileMark;
seek(((BufferedRandomAccessFileMark) mark).pointer);
}
public long bytesPastMark(DataPosition mark)
{
assert mark instanceof BufferedRandomAccessFileMark;
long bytes = current() - ((BufferedRandomAccessFileMark) mark).pointer;
assert bytes >= 0;
return bytes;
}
/**
* @return true if there is no more data to read
*/
public boolean isEOF()
{
return current() == length();
}
public long bytesRemaining()
{
return length() - getFilePointer();
}
@Override
public int available() throws IOException
{
return Ints.saturatedCast(bytesRemaining());
}
@Override
public void close()
{
// close needs to be idempotent.
if (buffer == null)
return;
bufferHolder.release();
rebufferer.closeReader();
buffer = null;
bufferHolder = null;
//For performance reasons we don't keep a reference to the file
//channel so we don't close it
}
@Override
public String toString()
{
return getClass().getSimpleName() + ':' + rebufferer;
}
/**
* Class to hold a mark to the position of the file
*/
private static class BufferedRandomAccessFileMark implements DataPosition
{
final long pointer;
private BufferedRandomAccessFileMark(long pointer)
{
this.pointer = pointer;
}
}
@Override
public void seek(long newPosition)
{
if (newPosition < 0)
throw new IllegalArgumentException("new position should not be negative");
if (buffer == null)
throw new IllegalStateException("Attempted to seek in a closed RAR");
long bufferOffset = bufferHolder.offset();
if (newPosition >= bufferOffset && newPosition < bufferOffset + buffer.limit())
{
buffer.position((int) (newPosition - bufferOffset));
return;
}
if (newPosition > length())
throw new IllegalArgumentException(String.format("Unable to seek to position %d in %s (%d bytes) in read-only mode",
newPosition, getPath(), length()));
reBufferAt(newPosition);
}
@Override
public int skipBytes(int n) throws IOException
{
if (n <= 0)
return 0;
if (buffer == null)
throw new IOException("Attempted skipBytes() on a closed RAR");
long current = current();
long newPosition = Math.min(current + n, length());
n = (int)(newPosition - current);
seek(newPosition);
return n;
}
/**
* Reads a line of text form the current position in this file. A line is
* represented by zero or more characters followed by {@code '\n'}, {@code
* '\r'}, {@code "\r\n"} or the end of file marker. The string does not
* include the line terminating sequence.
*
* Blocks until a line terminating sequence has been read, the end of the
* file is reached or an exception is thrown.
*
* @return the contents of the line or {@code null} if no characters have
* been read before the end of the file has been reached.
* @throws IOException if this file is closed or another I/O error occurs.
*/
public final String readLine() throws IOException
{
StringBuilder line = new StringBuilder(80); // Typical line length
boolean foundTerminator = false;
long unreadPosition = -1;
while (true)
{
int nextByte = read();
switch (nextByte)
{
case -1:
return line.length() != 0 ? line.toString() : null;
case (byte) '\r':
if (foundTerminator)
{
seek(unreadPosition);
return line.toString();
}
foundTerminator = true;
/* Have to be able to peek ahead one byte */
unreadPosition = getPosition();
break;
case (byte) '\n':
return line.toString();
default:
if (foundTerminator)
{
seek(unreadPosition);
return line.toString();
}
line.append((char) nextByte);
}
}
}
public long length()
{
return rebufferer.fileLength();
}
public long getPosition()
{
return current();
}
public double getCrcCheckChance()
{
return rebufferer.getCrcCheckChance();
}
// A wrapper of the RandomAccessReader that closes the channel when done.
// For performance reasons RAR does not increase the reference count of
// a channel but assumes the owner will keep it open and close it,
// see CASSANDRA-9379, this thin class is just for those cases where we do
// not have a shared channel.
static class RandomAccessReaderWithOwnChannel extends RandomAccessReader
{
RandomAccessReaderWithOwnChannel(Rebufferer rebufferer)
{
super(rebufferer);
}
@Override
public void close()
{
try
{
super.close();
}
finally
{
try
{
rebufferer.close();
}
finally
{
getChannel().close();
}
}
}
}
/**
* Open a RandomAccessReader (not compressed, not mmapped, no read throttling) that will own its channel.
*
* @param file File to open for reading
* @return new RandomAccessReader that owns the channel opened in this method.
*/
@SuppressWarnings("resource")
public static RandomAccessReader open(File file)
{
ChannelProxy channel = new ChannelProxy(file);
try
{
ChunkReader reader = new SimpleChunkReader(channel, -1, BufferType.OFF_HEAP, DEFAULT_BUFFER_SIZE);
Rebufferer rebufferer = reader.instantiateRebufferer();
return new RandomAccessReaderWithOwnChannel(rebufferer);
}
catch (Throwable t)
{
channel.close();
throw t;
}
}
}
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