/*
* 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.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.io.FSReadError;
import org.apache.cassandra.utils.Pair;
/**
* Abstracts a read-only file that has been split into segments, each of which can be represented by an independent
* FileDataInput. Allows for iteration over the FileDataInputs, or random access to the FileDataInput for a given
* position.
*
* The JVM can only map up to 2GB at a time, so each segment is at most that size when using mmap i/o. If a segment
* would need to be longer than 2GB, that segment will not be mmap'd, and a new RandomAccessFile will be created for
* each access to that segment.
*/
public abstract class SegmentedFile
{
public final String path;
public final long length;
// This differs from length for compressed files (but we still need length for
// SegmentIterator because offsets in the file are relative to the uncompressed size)
public final long onDiskLength;
/**
* Use getBuilder to get a Builder to construct a SegmentedFile.
*/
SegmentedFile(String path, long length)
{
this(path, length, length);
}
protected SegmentedFile(String path, long length, long onDiskLength)
{
this.path = path;
this.length = length;
this.onDiskLength = onDiskLength;
}
/**
* @return A SegmentedFile.Builder.
*/
public static Builder getBuilder(Config.DiskAccessMode mode)
{
return mode == Config.DiskAccessMode.mmap
? new MmappedSegmentedFile.Builder()
: new BufferedSegmentedFile.Builder();
}
public static Builder getCompressedBuilder()
{
return new CompressedSegmentedFile.Builder();
}
public abstract FileDataInput getSegment(long position);
/**
* @return An Iterator over segments, beginning with the segment containing the given position: each segment must be closed after use.
*/
public Iterator<FileDataInput> iterator(long position, int bufferSize)
{
return new SegmentIterator(position);
}
/**
* Do whatever action is needed to reclaim ressources used by this SegmentedFile.
*/
public abstract void cleanup();
/**
* Collects potential segmentation points in an underlying file, and builds a SegmentedFile to represent it.
*/
public static abstract class Builder
{
/**
* Adds a position that would be a safe place for a segment boundary in the file. For a block/row based file
* format, safe boundaries are block/row edges.
* @param boundary The absolute position of the potential boundary in the file.
*/
public abstract void addPotentialBoundary(long boundary);
/**
* Called after all potential boundaries have been added to apply this Builder to a concrete file on disk.
* @param path The file on disk.
*/
public abstract SegmentedFile complete(String path);
public void serializeBounds(DataOutput dos) throws IOException
{
dos.writeUTF(DatabaseDescriptor.getDiskAccessMode().name());
}
public void deserializeBounds(DataInput dis) throws IOException
{
if (!dis.readUTF().equals(DatabaseDescriptor.getDiskAccessMode().name()))
throw new IOException("Cannot deserialize SSTable Summary component because the DiskAccessMode was changed!");
}
}
static final class Segment extends Pair<Long, MappedByteBuffer> implements Comparable<Segment>
{
public Segment(long offset, MappedByteBuffer segment)
{
super(offset, segment);
}
public final int compareTo(Segment that)
{
return (int)Math.signum(this.left - that.left);
}
}
/**
* A lazy Iterator over segments in forward order from the given position.
*/
final class SegmentIterator implements Iterator<FileDataInput>
{
private long nextpos;
public SegmentIterator(long position)
{
this.nextpos = position;
}
public boolean hasNext()
{
return nextpos < length;
}
public FileDataInput next()
{
long position = nextpos;
if (position >= length)
throw new NoSuchElementException();
FileDataInput segment = getSegment(nextpos);
try
{
nextpos = nextpos + segment.bytesRemaining();
}
catch (IOException e)
{
throw new FSReadError(e, path);
}
return segment;
}
public void remove() { throw new UnsupportedOperationException(); }
}
@Override
public String toString() {
return getClass().getSimpleName() + "(path='" + path + "'" +
", length=" + length +
")";
}
}