/*
 * 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.core.fs.local;

import org.apache.flink.annotation.Internal;
import org.apache.flink.core.fs.FSDataInputStream;

import javax.annotation.Nonnull;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

/**
 * The <code>LocalDataInputStream</code> class is a wrapper class for a data
 * input stream to the local file system.
 */
@Internal
public class LocalDataInputStream extends FSDataInputStream {

	/** The file input stream used to read data from.*/
	private final FileInputStream fis;
	private final FileChannel fileChannel;

	/**
	 * Constructs a new <code>LocalDataInputStream</code> object from a given {@link File} object.
	 *
	 * @param file The File the data stream is read from
	 *
	 * @throws IOException Thrown if the data input stream cannot be created.
	 */
	public LocalDataInputStream(File file) throws IOException {
		this.fis = new FileInputStream(file);
		this.fileChannel = fis.getChannel();
	}

	@Override
	public void seek(long desired) throws IOException {
		if (desired != getPos()) {
			this.fileChannel.position(desired);
		}
	}

	@Override
	public long getPos() throws IOException {
		return this.fileChannel.position();
	}

	@Override
	public int read() throws IOException {
		return this.fis.read();
	}

	@Override
	public int read(@Nonnull byte[] buffer, int offset, int length) throws IOException {
		return this.fis.read(buffer, offset, length);
	}

	@Override
	public void close() throws IOException {
		// According to javadoc, this also closes the channel
		this.fis.close();
	}

	@Override
	public int available() throws IOException {
		return this.fis.available();
	}

	@Override
	public long skip(final long n) throws IOException {
		return this.fis.skip(n);
	}
}