org.apache.flink.runtime.util.NioBufferedFileInputStream Maven / Gradle / Ivy

/*
 * 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.flink.runtime.util;

import java.io.IOException;
import java.io.InputStream;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;

import sun.misc.Cleaner;
import sun.nio.ch.DirectBuffer;

/**
 * {@link InputStream} implementation which uses direct buffer
 * to read a file to avoid extra copy of data between Java and
 * native memory which happens when using {@link java.io.BufferedInputStream}.
 * Unfortunately, this is not something already available in JDK,
 * {@link sun.nio.ch.ChannelInputStream} supports reading a file using nio,
 * but does not support buffering.
 */
public final class NioBufferedFileInputStream extends InputStream {

	private final ByteBuffer byteBuffer;

	private final FileChannel fileChannel;

	public NioBufferedFileInputStream(FileChannel fileChannel,
			int bufferSizeInBytes) throws IOException {
		byteBuffer = ByteBuffer.allocateDirect(bufferSizeInBytes);
		this.fileChannel = fileChannel;
		byteBuffer.flip();
	}

	/**
	 * Checks whether data is left to be read from the input stream.
	 *
	 * @return true if data is left, false otherwise
	 */
	private boolean refill() throws IOException {
		if (!byteBuffer.hasRemaining()) {
			byteBuffer.clear();
			int nRead = 0;
			while (nRead == 0) {
				nRead = fileChannel.read(byteBuffer);
			}
			if (nRead < 0) {
				return false;
			}
			byteBuffer.flip();
		}
		return true;
	}

	@Override
	public synchronized int read() throws IOException {
		if (!refill()) {
			return -1;
		}
		return byteBuffer.get() & 0xFF;
	}

	@Override
	public synchronized int read(byte[] b, int offset, int len) throws IOException {
		if (offset < 0 || len < 0 || offset + len < 0 || offset + len > b.length) {
			throw new IndexOutOfBoundsException();
		}
		if (!refill()) {
			return -1;
		}
		len = Math.min(len, byteBuffer.remaining());
		byteBuffer.get(b, offset, len);
		return len;
	}

	public synchronized int read(ByteBuffer b) throws IOException {
		if (!refill()) {
			return -1;
		}
		int len = b.remaining();
		len = Math.min(len, byteBuffer.remaining());
		if (len > 0) {
			ByteBuffer src = byteBuffer.duplicate();
			src.limit(src.position() + len);
			b.put(src);
			byteBuffer.position(src.position());
		}
		return len;
	}

	public synchronized void continuousRead(ByteBuffer b) throws IOException {
		while (b.remaining() > 0) {
			int result = read(b);
			if (result == -1) {
				return;
			}
		}
	}

	@Override
	public synchronized int available() throws IOException {
		long avail = fileChannel.size() - fileChannel.position() + byteBuffer.remaining();
		return avail > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) avail;
	}

	public long position() throws IOException {
		return fileChannel.position() - byteBuffer.remaining();
	}

	public long size() throws IOException {
		return fileChannel.size();
	}

	@Override
	public synchronized long skip(long n) throws IOException {
		if (n <= 0L) {
			return 0L;
		}
		if (byteBuffer.remaining() >= n) {
			// The buffered content is enough to skip
			byteBuffer.position(byteBuffer.position() + (int) n);
			return n;
		}
		long skippedFromBuffer = byteBuffer.remaining();
		long toSkipFromFileChannel = n - skippedFromBuffer;
		// Discard everything we have read in the buffer.
		byteBuffer.position(0);
		byteBuffer.flip();
		return skippedFromBuffer + skipFromFileChannel(toSkipFromFileChannel);
	}

	private long skipFromFileChannel(long n) throws IOException {
		long currentFilePosition = fileChannel.position();
		long size = fileChannel.size();
		if (n > size - currentFilePosition) {
			fileChannel.position(size);
			return size - currentFilePosition;
		} else {
			fileChannel.position(currentFilePosition + n);
			return n;
		}
	}

	public void clearBuffer() {
		byteBuffer.clear();
		byteBuffer.flip();
	}

	@Override
	public synchronized void close() throws IOException {
		if (byteBuffer != null && byteBuffer instanceof MappedByteBuffer) {
			Cleaner cleaner = ((DirectBuffer) byteBuffer).cleaner();
			if (cleaner != null) {
				cleaner.clean();
			}
		}
	}

	@Override
	protected void finalize() throws IOException {
		close();
	}
}