/**
*
* 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.*;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
public class MappedFileDataInput extends AbstractDataInput implements FileDataInput
{
private final MappedByteBuffer buffer;
private final String filename;
private int position;
public MappedFileDataInput(FileInputStream stream, String filename, int position) throws IOException
{
FileChannel channel = stream.getChannel();
buffer = channel.map(FileChannel.MapMode.READ_ONLY, position, channel.size());
this.filename = filename;
this.position = position;
}
public MappedFileDataInput(MappedByteBuffer buffer, String filename, int position)
{
assert buffer != null;
this.buffer = buffer;
this.filename = filename;
this.position = position;
}
// don't make this public, this is only for seeking WITHIN the current mapped segment
protected void seekInternal(int pos)
{
position = pos;
}
@Override
protected int getPosition()
{
return position;
}
@Override
public boolean markSupported()
{
return false;
}
public void reset(FileMark mark) throws IOException
{
assert mark instanceof MappedFileDataInputMark;
seekInternal(((MappedFileDataInputMark) mark).position);
}
public FileMark mark()
{
return new MappedFileDataInputMark(position);
}
public long bytesPastMark(FileMark mark)
{
assert mark instanceof MappedFileDataInputMark;
assert position >= ((MappedFileDataInputMark) mark).position;
return position - ((MappedFileDataInputMark) mark).position;
}
public boolean isEOF() throws IOException
{
return position == buffer.capacity();
}
public long bytesRemaining() throws IOException
{
return buffer.capacity() - position;
}
public String getPath()
{
return filename;
}
public int read() throws IOException
{
if (isEOF())
return -1;
return buffer.get(position++) & 0xFF;
}
/**
* Does the same thing as <code>readFully</code> do but without copying data (thread safe)
* @param length length of the bytes to read
* @return buffer with portion of file content
* @throws IOException on any fail of I/O operation
*/
public synchronized ByteBuffer readBytes(int length) throws IOException
{
int remaining = buffer.remaining() - position;
assert length <= remaining
: String.format("mmap segment underflow; remaining is %d but %d requested", remaining, length);
ByteBuffer bytes = buffer.duplicate();
bytes.position(buffer.position() + position).limit(buffer.position() + position + length);
position += length;
return bytes;
}
@Override
public final void readFully(byte[] buffer) throws IOException
{
throw new UnsupportedOperationException("use readBytes instead");
}
@Override
public final void readFully(byte[] buffer, int offset, int count) throws IOException
{
throw new UnsupportedOperationException("use readBytes instead");
}
public int skipBytes(int n) throws IOException
{
assert n >= 0 : "skipping negative bytes is illegal: " + n;
if (n == 0)
return 0;
int oldPosition = position;
assert ((long)oldPosition) + n <= Integer.MAX_VALUE;
position = Math.min(buffer.capacity(), position + n);
return position - oldPosition;
}
private static class MappedFileDataInputMark implements FileMark
{
int position;
MappedFileDataInputMark(int position)
{
this.position = position;
}
}
@Override
public String toString() {
return getClass().getSimpleName() + "(" +
"filename='" + filename + "'" +
", position=" + position +
")";
}
}