org.h2.store.fs.FilePathNio Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.store.fs;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.nio.channels.NonWritableChannelException;
/**
* This file system stores files on disk and uses java.nio to access the files.
* This class uses FileChannel.
*/
public class FilePathNio extends FilePathWrapper {
@Override
public FileChannel open(String mode) throws IOException {
return new FileNio(name.substring(getScheme().length() + 1), mode);
}
@Override
public String getScheme() {
return "nio";
}
}
/**
* File which uses NIO FileChannel.
*/
class FileNio extends FileBase {
private final String name;
private final FileChannel channel;
FileNio(String fileName, String mode) throws IOException {
this.name = fileName;
channel = new RandomAccessFile(fileName, mode).getChannel();
}
@Override
public void implCloseChannel() throws IOException {
channel.close();
}
@Override
public long position() throws IOException {
return channel.position();
}
@Override
public long size() throws IOException {
return channel.size();
}
@Override
public int read(ByteBuffer dst) throws IOException {
return channel.read(dst);
}
@Override
public FileChannel position(long pos) throws IOException {
channel.position(pos);
return this;
}
@Override
public int read(ByteBuffer dst, long position) throws IOException {
return channel.read(dst, position);
}
@Override
public int write(ByteBuffer src, long position) throws IOException {
return channel.write(src, position);
}
@Override
public FileChannel truncate(long newLength) throws IOException {
long size = channel.size();
if (newLength < size) {
long pos = channel.position();
channel.truncate(newLength);
long newPos = channel.position();
if (pos < newLength) {
// position should stay
// in theory, this should not be needed
if (newPos != pos) {
channel.position(pos);
}
} else if (newPos > newLength) {
// looks like a bug in this FileChannel implementation, as
// the documentation says the position needs to be changed
channel.position(newLength);
}
}
return this;
}
@Override
public void force(boolean metaData) throws IOException {
channel.force(metaData);
}
@Override
public int write(ByteBuffer src) throws IOException {
try {
return channel.write(src);
} catch (NonWritableChannelException e) {
throw new IOException("read only");
}
}
@Override
public synchronized FileLock tryLock(long position, long size,
boolean shared) throws IOException {
return channel.tryLock(position, size, shared);
}
@Override
public String toString() {
return "nio:" + name;
}
}