/*
* 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.compress;
import java.io.EOFException;
import java.io.File;
import java.io.IOException;
import java.util.zip.Adler32;
import java.util.zip.Checksum;
import org.apache.cassandra.io.FSReadError;
import org.apache.cassandra.io.FSWriteError;
import org.apache.cassandra.io.sstable.CorruptSSTableException;
import org.apache.cassandra.io.sstable.metadata.MetadataCollector;
import org.apache.cassandra.io.util.FileMark;
import org.apache.cassandra.io.util.SequentialWriter;
public class CompressedSequentialWriter extends SequentialWriter
{
public static SequentialWriter open(String dataFilePath,
String indexFilePath,
boolean skipIOCache,
CompressionParameters parameters,
MetadataCollector sstableMetadataCollector)
{
return new CompressedSequentialWriter(new File(dataFilePath), indexFilePath, skipIOCache, parameters, sstableMetadataCollector);
}
// holds offset in the file where current chunk should be written
// changed only by flush() method where data buffer gets compressed and stored to the file
private long chunkOffset = 0;
// index file writer (random I/O)
private final CompressionMetadata.Writer metadataWriter;
private final ICompressor compressor;
// used to store compressed data
private final ICompressor.WrappedArray compressed;
// holds a number of already written chunks
private int chunkCount = 0;
private final Checksum checksum = new Adler32();
private long originalSize = 0, compressedSize = 0;
private final MetadataCollector sstableMetadataCollector;
public CompressedSequentialWriter(File file,
String indexFilePath,
boolean skipIOCache,
CompressionParameters parameters,
MetadataCollector sstableMetadataCollector)
{
super(file, parameters.chunkLength(), skipIOCache);
this.compressor = parameters.sstableCompressor;
// buffer for compression should be the same size as buffer itself
compressed = new ICompressor.WrappedArray(new byte[compressor.initialCompressedBufferLength(buffer.length)]);
/* Index File (-CompressionInfo.db component) and it's header */
metadataWriter = CompressionMetadata.Writer.open(indexFilePath);
metadataWriter.writeHeader(parameters);
this.sstableMetadataCollector = sstableMetadataCollector;
}
@Override
public long getOnDiskFilePointer()
{
try
{
return out.getFilePointer();
}
catch (IOException e)
{
throw new FSReadError(e, getPath());
}
}
@Override
public void sync()
{
throw new UnsupportedOperationException();
}
@Override
public void flush()
{
throw new UnsupportedOperationException();
}
@Override
protected void flushData()
{
seekToChunkStart();
int compressedLength;
try
{
// compressing data with buffer re-use
compressedLength = compressor.compress(buffer, 0, validBufferBytes, compressed, 0);
}
catch (IOException e)
{
throw new RuntimeException("Compression exception", e); // shouldn't happen
}
originalSize += validBufferBytes;
compressedSize += compressedLength;
// update checksum
checksum.update(compressed.buffer, 0, compressedLength);
try
{
// write an offset of the newly written chunk to the index file
metadataWriter.writeLong(chunkOffset);
chunkCount++;
assert compressedLength <= compressed.buffer.length;
// write data itself
out.write(compressed.buffer, 0, compressedLength);
// write corresponding checksum
out.writeInt((int) checksum.getValue());
}
catch (IOException e)
{
throw new FSWriteError(e, getPath());
}
// reset checksum object to the blank state for re-use
checksum.reset();
// next chunk should be written right after current + length of the checksum (int)
chunkOffset += compressedLength + 4;
}
@Override
public FileMark mark()
{
return new CompressedFileWriterMark(chunkOffset, current, validBufferBytes, chunkCount + 1);
}
@Override
public synchronized void resetAndTruncate(FileMark mark)
{
assert mark instanceof CompressedFileWriterMark;
CompressedFileWriterMark realMark = (CompressedFileWriterMark) mark;
// reset position
current = realMark.uncDataOffset;
if (realMark.chunkOffset == chunkOffset) // current buffer
{
// just reset a buffer offset and return
validBufferBytes = realMark.bufferOffset;
return;
}
// synchronize current buffer with disk
// because we don't want any data loss
syncInternal();
// setting marker as a current offset
chunkOffset = realMark.chunkOffset;
// compressed chunk size (- 4 bytes reserved for checksum)
int chunkSize = (int) (metadataWriter.chunkOffsetBy(realMark.nextChunkIndex) - chunkOffset - 4);
if (compressed.buffer.length < chunkSize)
compressed.buffer = new byte[chunkSize];
try
{
out.seek(chunkOffset);
out.readFully(compressed.buffer, 0, chunkSize);
try
{
// repopulate buffer
compressor.uncompress(compressed.buffer, 0, chunkSize, buffer, 0);
}
catch (IOException e)
{
throw new CorruptBlockException(getPath(), chunkOffset, chunkSize);
}
checksum.update(compressed.buffer, 0, chunkSize);
if (out.readInt() != (int) checksum.getValue())
throw new CorruptBlockException(getPath(), chunkOffset, chunkSize);
}
catch (CorruptBlockException e)
{
throw new CorruptSSTableException(e, getPath());
}
catch (EOFException e)
{
throw new CorruptSSTableException(new CorruptBlockException(getPath(), chunkOffset, chunkSize), getPath());
}
catch (IOException e)
{
throw new FSReadError(e, getPath());
}
checksum.reset();
// reset buffer
validBufferBytes = realMark.bufferOffset;
bufferOffset = current - validBufferBytes;
chunkCount = realMark.nextChunkIndex - 1;
// truncate data and index file
truncate(chunkOffset);
metadataWriter.resetAndTruncate(realMark.nextChunkIndex);
}
/**
* Seek to the offset where next compressed data chunk should be stored.
*/
private void seekToChunkStart()
{
if (getOnDiskFilePointer() != chunkOffset)
{
try
{
out.seek(chunkOffset);
}
catch (IOException e)
{
throw new FSReadError(e, getPath());
}
}
}
@Override
public void close()
{
if (buffer == null)
return; // already closed
super.close();
sstableMetadataCollector.addCompressionRatio(compressedSize, originalSize);
metadataWriter.finalizeHeader(current, chunkCount);
try
{
metadataWriter.close();
}
catch (IOException e)
{
throw new FSWriteError(e, getPath());
}
}
/**
* Class to hold a mark to the position of the file
*/
protected static class CompressedFileWriterMark implements FileMark
{
// chunk offset in the compressed file
final long chunkOffset;
// uncompressed data offset (real data offset)
final long uncDataOffset;
final int bufferOffset;
final int nextChunkIndex;
public CompressedFileWriterMark(long chunkOffset, long uncDataOffset, int bufferOffset, int nextChunkIndex)
{
this.chunkOffset = chunkOffset;
this.uncDataOffset = uncDataOffset;
this.bufferOffset = bufferOffset;
this.nextChunkIndex = nextChunkIndex;
}
}
}