/*
 *
 * This file is part of the iText (R) project.
    Copyright (c) 1998-2017 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.io.RandomAccessFile;

/**
 * 
 * A RandomAccessSource that uses a {@link RandomAccessFile} as it's source
 * Note: Unlike most of the RandomAccessSource implementations, this class is not thread safe
 */
class RAFRandomAccessSource implements RandomAccessSource {
	/**
	 * The source
	 */
	private final RandomAccessFile raf;
	
	/**
	 * The length of the underling RAF.  Note that the length is cached at construction time to avoid the possibility
	 * of IOExceptions when reading the length.
	 */
	private final long length;
	
	/**
	 * Creates this object
	 * @param raf the source for this RandomAccessSource
	 * @throws IOException if the RAF can't be read
	 */
	public RAFRandomAccessSource(RandomAccessFile raf) throws IOException {
		this.raf = raf;
		length = raf.length();
	}

	/**
	 * {@inheritDoc}
	 */
	// TODO: test to make sure we are handling the length properly (i.e. is raf.length() the last byte in the file, or one past the last byte?)
	public int get(long position) throws IOException {
		if (position > raf.length())
			return -1;
		
		// Not thread safe!
		raf.seek(position);
		
		return raf.read();
	}

	/**
	 * {@inheritDoc}
	 */
	public int get(long position, byte[] bytes, int off, int len) throws IOException {
		if (position > length)
			return -1;
		
		// Not thread safe!
		raf.seek(position);

		return raf.read(bytes, off, len);
	}

	/**
	 * {@inheritDoc}
	 * Note: the length is determined when the {@link RAFRandomAccessSource} is constructed.  If the file length changes
	 * after construction, that change will not be reflected in this call.
	 */
	public long length() {
		return length;
	}

	/**
	 * Closes the underlying RandomAccessFile
	 */
	public void close() throws IOException {
		raf.close();
	}

}
