itextpdf-master/itext/src/main/java/com/itextpdf/text/io/FileChannelRandomAccessSource.java
/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2022 iText Group NV
 * Authors: Kevin Day, Bruno Lowagie, et al.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * ITEXT GROUP. ITEXT GROUP DISCLAIMS THE WARRANTY OF NON INFRINGEMENT
 * OF THIRD PARTY RIGHTS.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Affero General License for more
 * details. You should have received a copy of the GNU Affero General License
 * along with this program; if not, see http://www.gnu.org/licenses or write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
 * MA, 02110-1301 USA, or download the license from the following URL:
 * http://itextpdf.com/terms-of-use/
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General License.
 *
 * In accordance with Section 7(b) of the GNU Affero General License, a covered
 * work must retain the producer line in every PDF that is created or
 * manipulated using iText.
 *
 * You can be released from the requirements of the license by purchasing a
 * commercial license. Buying such a license is mandatory as soon as you develop
 * commercial activities involving the iText software without disclosing the
 * source code of your own applications. These activities include: offering paid
 * services to customers as an ASP, serving PDFs on the fly in a web
 * application, shipping iText with a closed source product.
 *
 * For more information, please contact iText Software Corp. at this address:
 * sales@itextpdf.com
 */
package com.itextpdf.text.io;

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

/**
 * A RandomAccessSource that is based on an underlying {@link FileChannel}.  The entire channel will be mapped into memory for efficient reads.
 * @since 5.3.5
 */
public class FileChannelRandomAccessSource implements RandomAccessSource {

    /**
     * The channel this source is based on
     */
    private final FileChannel channel;
    
    /**
     * Tracks the actual mapping
     */
    private final MappedChannelRandomAccessSource source;

    /**
     * Constructs a new {@link FileChannelRandomAccessSource} based on the specified FileChannel.  The entire source channel will be mapped into memory.
     * @param channel the channel to use as the backing store
     * @throws IOException if the channel cannot be opened or mapped
     */
    public FileChannelRandomAccessSource(FileChannel channel) throws IOException {
		this.channel = channel;
		if(channel.size() == 0)
			throw new IOException("File size is 0 bytes");
		source = new MappedChannelRandomAccessSource(channel, 0, channel.size());
		source.open();
	}
    
	
    /**
     * {@inheritDoc}
     * Cleans the mapped bytebuffers and closes the channel
     */
    public void close() throws IOException {
		source.close();
        channel.close();
    }


    /**
     * {@inheritDoc}
     */
	public int get(long position) throws IOException {
		return source.get(position);
	}


    /**
     * {@inheritDoc}
     */
	public int get(long position, byte[] bytes, int off, int len) throws IOException {
		return source.get(position, bytes, off, len);
	}


    /**
     * {@inheritDoc}
     */
	public long length() {
		return source.length();
	}

}
