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package io.skas.melbjvm.nio2;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.AsynchronousFileChannel;
import java.nio.channels.CompletionHandler;
import java.nio.file.Path;
import java.nio.file.StandardOpenOption;
/**
* @author Szymon Szukalski [szymon.szukalski@gmail.com]
*/
public class AsynchronousFileReader implements CompletionHandler<Integer, ByteBuffer> {
public static final Logger LOG = LoggerFactory.getLogger(AsynchronousFileReader.class);
public static final int BYTES_IN_MEGABYTE = 1048576;
private Long position;
private Path path;
private ByteBuffer buffer;
private AsynchronousFileChannel asynchronousFileChannel;
public AsynchronousFileReader(Path path) {
this.position = 0L;
this.path = path;
this.buffer = ByteBuffer.allocate(BYTES_IN_MEGABYTE);
LOG.info("reading {}...", path);
this.openChannel();
this.readChannel(0);
}
private void openChannel() {
try {
this.asynchronousFileChannel = AsynchronousFileChannel.open(path, StandardOpenOption.READ);
} catch (IOException e) {
e.printStackTrace();
}
}
private void closeChannel() {
try {
this.asynchronousFileChannel.close();
} catch (IOException e) {
e.printStackTrace();
}
}
private void readChannel(long position) {
asynchronousFileChannel.read(buffer, position, buffer, this);
}
@Override
public void completed(Integer result, ByteBuffer buffer) {
if (result < 0) {
closeChannel();
LOG.debug("read: {} megabytes", position / BYTES_IN_MEGABYTE);
} else {
position += result;
if (buffer.hasRemaining()) {
readChannel(position);
} else {
buffer.flip();
// Do something with the content of the buffer
buffer.clear();
this.readChannel(position);
}
}
}
@Override
public void failed(Throwable exc, ByteBuffer buffer) {
LOG.error("read failed: {}", exc.getMessage());
exc.printStackTrace();
}
}
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