protocols/bundles/org.eclipse.ecf.protocol.bittorrent/src/org/eclipse/ecf/protocol/bittorrent/TorrentFile.java - ecf/org.eclipse.ecf - Git at Google

 /*******************************************************************************
  * Copyright (c) 2006, 2008 Remy Suen, Composent Inc., and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *    Remy Suen <remy.suen@gmail.com> - initial API and implementation
  ******************************************************************************/
 package org.eclipse.ecf.protocol.bittorrent;

 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 import java.util.List;

 import org.eclipse.ecf.protocol.bittorrent.internal.encode.BEncodedDictionary;
 import org.eclipse.ecf.protocol.bittorrent.internal.encode.Decode;

 /**
  * The <code>TorrentFile</code> class is a representation of the information
  * stored within a <code>.torrent</code> file. Files can be set with the
  * {@link #setTargetFile(File)} method and then have its integrity checked
  * against the torrent's hash sum values {@link #validate()} method.
  */
 public class TorrentFile {

 	static MessageDigest shaDigest;

 	private final String[] filenames;

 	/**
 	 * An array of Strings that corresponds to the SHA-1 hash of each piece.
 	 */
 	private final String[] pieces;

 	private final long[] lengths;

 	private final byte[] torrentData;

 	private final ByteBuffer buffer;

 	private final BEncodedDictionary dictionary;

 	private final String tracker;

 	private final String infoHash;

 	private final String hexHash;

 	private File file;

 	private String name;

 	private long total;

 	private final int pieceLength;

 	private final int numPieces;

 	static {
 		try {
 			shaDigest = MessageDigest.getInstance("SHA-1"); //$NON-NLS-1$
 		} catch (final NoSuchAlgorithmException e) {
 			throw new RuntimeException(e);
 		}
 	}

 	/**
 	 * Creates a new <code>Torrent</code> to analyze the provided torrent
 	 * file.
 	 *
 	 * @param file
 	 *            the torrent file
 	 * @throws IllegalArgumentException
 	 *             If <code>file</code> is <code>null</code> or a directory
 	 * @throws IOException
 	 *             If an I/O error occurs whilst analyzing the torrent file
 	 */
 	public TorrentFile(File file) throws IllegalArgumentException, IOException {
 		if (file == null) {
 			throw new IllegalArgumentException("The file cannot be null"); //$NON-NLS-1$
 		} else if (file.isDirectory()) {
 			throw new IllegalArgumentException("The provided file is a directory"); //$NON-NLS-1$
 		}
 		name = file.getName();
 		if (name.endsWith(".torrent")) { //$NON-NLS-1$
 			name = name.substring(0, name.length() - 8);
 		}

 		dictionary = Decode.bDecode(new FileInputStream(file));
 		torrentData = dictionary.toString().getBytes("ISO-8859-1"); //$NON-NLS-1$
 		tracker = (String) dictionary.get("announce"); //$NON-NLS-1$
 		final BEncodedDictionary info = (BEncodedDictionary) dictionary.get("info"); //$NON-NLS-1$
 		final List list = (List) info.get("files"); //$NON-NLS-1$
 		if (list != null) {
 			filenames = new String[list.size()];
 			lengths = new long[filenames.length];
 			total = 0;
 			for (int i = 0; i < filenames.length; i++) {
 				final BEncodedDictionary aDictionary = (BEncodedDictionary) list.get(i);
 				lengths[i] = ((Long) aDictionary.get("length")).longValue(); //$NON-NLS-1$
 				total += lengths[i];
 				final List aList = (List) aDictionary.get("path"); //$NON-NLS-1$
 				final StringBuffer buffer = new StringBuffer();
 				synchronized (buffer) {
 					for (int j = 0; j < aList.size(); j++) {
 						buffer.append(aList.get(j)).append(File.separator);
 					}
 				}
 				filenames[i] = buffer.toString();
 			}
 		} else {
 			lengths = new long[] {((Long) info.get("length")).longValue()}; //$NON-NLS-1$
 			total = lengths[0];
 			filenames = new String[] {(String) info.get("name")}; //$NON-NLS-1$
 		}
 		pieceLength = ((Long) info.get("piece length")).intValue(); //$NON-NLS-1$
 		buffer = ByteBuffer.allocate(pieceLength);
 		final String shaPieces = (String) info.get("pieces"); //$NON-NLS-1$
 		pieces = new String[shaPieces.length() / 20];
 		for (int i = 0; i < pieces.length; i++) {
 			pieces[i] = shaPieces.substring(i * 20, i * 20 + 20);
 		}
 		numPieces = pieces.length;
 		infoHash = new String(shaDigest.digest(info.toString().getBytes("ISO-8859-1")), "ISO-8859-1"); //$NON-NLS-1$ //$NON-NLS-2$
 		final byte[] bytes = infoHash.getBytes("ISO-8859-1"); //$NON-NLS-1$
 		final StringBuffer hash = new StringBuffer(40);
 		for (int i = 0; i < bytes.length; i++) {
 			if (-1 < bytes[i] && bytes[i] < 16) {
 				hash.append('0');
 			}
 			hash.append(Integer.toHexString(0xff & bytes[i]));
 		}
 		hexHash = hash.toString();
 	}

 	private boolean hashCheckFile() throws FileNotFoundException, IOException {
 		final int remainder = (int) (file.length() % pieceLength);
 		int count = 0;
 		final FileChannel channel = new FileInputStream(file).getChannel();
 		while (channel.read(buffer) == pieceLength) {
 			buffer.rewind();
 			if (!pieces[count].equals(new String(shaDigest.digest(buffer.array()), "ISO-8859-1"))) { //$NON-NLS-1$
 				return false;
 			}
 			count++;
 		}
 		buffer.rewind();
 		shaDigest.update(buffer.array(), 0, remainder);
 		return pieces[pieces.length - 1].equals(new String(shaDigest.digest(), "ISO-8859-1")); //$NON-NLS-1$
 	}

 	private boolean hashCheckFolder() throws FileNotFoundException, IOException {
 		int read = 0;
 		int count = 0;
 		for (int i = 0; i < filenames.length; i++) {
 			final File download = new File(file.getAbsolutePath(), filenames[i]);
 			final FileChannel channel = new FileInputStream(download).getChannel();
 			while ((read += channel.read(buffer)) == pieceLength) {
 				buffer.rewind();
 				if (!pieces[count].equals(new String(shaDigest.digest(buffer.array()), "ISO-8859-1"))) { //$NON-NLS-1$
 					return false;
 				}
 				count++;
 				read = 0;
 			}
 		}
 		buffer.rewind();
 		shaDigest.update(buffer.array(), 0, read);
 		return pieces[pieces.length - 1].equals(new String(shaDigest.digest(), "ISO-8859-1")); //$NON-NLS-1$
 	}

 	/**
 	 * Checks the integrity of the target file or folder as set by
 	 * {@link #setTargetFile(File)} to determine whether its contents pass all
 	 * of the hash checks.
 	 *
 	 * @return <code>true</code> if and only if every hash check has been
 	 *         passed, <code>false</code> otherwise
 	 * @throws FileNotFoundException
 	 *             If one of the files associated with the torrent could not be
 	 *             found
 	 * @throws IllegalStateException
 	 *             If the target file has not been set yet with
 	 *             {@link #setTargetFile(File)}
 	 * @throws IOException
 	 *             If an I/O error occurs while reading from the files
 	 */
 	public boolean validate() throws IllegalStateException, IOException {
 		if (file == null) {
 			throw new IllegalStateException("The target file for this torrent has not yet been set"); //$NON-NLS-1$
 		}
 		return file.isDirectory() ? hashCheckFolder() : hashCheckFile();
 	}

 	/**
 	 * Sets the target file or folder that this torrent should download to or
 	 * look for the corresponding files in.
 	 *
 	 * @param file
 	 *            the target file or folder to use, this should be a file if the
 	 *            torrent is a single file torrent or a folder if it has
 	 *            multiple files
 	 * @throws IllegalArgumentException
 	 *             If <code>file</code> is null or if <code>file</code> is a
 	 *             directory when this torrent is only using a single file
 	 */
 	public void setTargetFile(File file) throws IllegalArgumentException {
 		if (file == null) {
 			throw new IllegalArgumentException("The file cannot be null"); //$NON-NLS-1$
 		} else if (filenames.length == 1 && file.isDirectory()) {
 			throw new IllegalArgumentException("This torrent is downloading a file, the actual file should be set here and not a directory"); //$NON-NLS-1$
 		}
 		this.file = file;
 	}

 	/**
 	 * Returns the hash of the <code>info</code> dictionary specified by the
 	 * torrent's metainfo. This is primarily used for torrent identification
 	 * when sending messages to the tracker.
 	 *
 	 * @return the hash of the <code>info</code> dictionary within the
 	 *         torrent's metainfo, this will likely contain binary data and will
 	 *         not be human-readable as a result
 	 */
 	public String getInfoHash() {
 		return infoHash;
 	}

 	/**
 	 * Returns the hexadecimal representation of the hash returned from
 	 * {@link #getInfoHash()}. This string is forty characters long.
 	 *
 	 * @return the hexadecimal value of <code>getInfoHash()</code>
 	 */
 	public String getHexHash() {
 		return hexHash;
 	}

 	/**
 	 * Retrieve the specified lengths of the files contained within this
 	 * torrent. Every length contained within the returned array corresponds to
 	 * a file's name specified by {@link #getFilenames()}.
 	 *
 	 * @return an array of lengths for each of the files specified within the
 	 *         torrent's metainfo
 	 */
 	public long[] getLengths() {
 		return lengths;
 	}

 	/**
 	 * Returns the length of a piece.
 	 *
 	 * @return a piece's length
 	 */
 	public int getPieceLength() {
 		return pieceLength;
 	}

 	/**
 	 * Retrieves the URL of the tracker that's handling the requests for this
 	 * torrent.
 	 *
 	 * @return the tracker's URL
 	 */
 	public String getTracker() {
 		return tracker;
 	}

 	/**
 	 * Returns a string array that contains the SHA-1 hash of each of the pieces
 	 * defined by the torrent's metainfo.
 	 *
 	 * @return an array of strings with the SHA-1 hash for each piece of data
 	 */
 	public String[] getPieces() {
 		return pieces;
 	}

 	/**
 	 * Returns the number of pieces associated with this torrent.
 	 *
 	 * @return the number of pieces
 	 */
 	public int getNumPieces() {
 		return numPieces;
 	}

 	/**
 	 * Retrieves the names of all of the files' that is specified by this
 	 * <code>Torrent</code>. All of the files' lengths can be matched up
 	 * against the long value stored within the returned array from
 	 * {@link #getLengths()}.
 	 *
 	 * @return an array of names for all of the files specified by the metadata
 	 */
 	public String[] getFilenames() {
 		return filenames;
 	}

 	/**
 	 * Retrieves the name of this torrent file. This is dictated by whatever is
 	 * before the ending <code>.torrent</code> extension. If no such extension
 	 * exists, the entire file's name will be returned.
 	 *
 	 * @return the name of this torrent without the trailing
 	 *         <code>.torrent</code> extension, if present
 	 */
 	public String getName() {
 		return name;
 	}

 	/**
 	 * Gets the file that has been set as the target file of this torrent per
 	 * {@link #setTargetFile(File)}.
 	 *
 	 * @return the target file for this torrent
 	 */
 	public File getTargetFile() {
 		return file;
 	}

 	/**
 	 * Returns whether this torrent is associated with multiple files or not.
 	 *
 	 * @return <code>true</code> if this torrent specifies multiple files,
 	 *         <code>false</code> otherwise
 	 */
 	public boolean isMultiFile() {
 		return lengths.length != 1;
 	}

 	/**
 	 * Retrieves the total length of all of the files specified within this
 	 * torrent. This is equivalent to the sum of all the lengths returned from
 	 * the array in {@link #getLengths()}.
 	 *
 	 * @return the combined length of all the files specified by this torrent
 	 */
 	public long getTotalLength() {
 		return total;
 	}

 	/**
 	 * Writes the contents of the file that was used to initialize this
 	 * <code>TorrentFile</code> onto the provided file.
 	 *
 	 * @param file
 	 *            the file to save to
 	 * @throws IOException
 	 *             If an I/O error occurs while trying to write to the file
 	 */
 	public void save(File file) throws IOException {
 		final FileOutputStream fos = new FileOutputStream(file);
 		fos.write(torrentData);
 		fos.flush();
 		fos.close();
 	}

 	/**
 	 * Returns whether this <code>TorrentFile</code> is equal to the given
 	 * object. The two are the same if their info hash section of the contained
 	 * metainfo is the same. If <code>other</code> is not an instance of a
 	 * <code>TorrentFile</code>, <code>false</code> is returned.
 	 * @param other
 	 *
 	 * @return <code>true</code> if <code>other</code> is a
 	 *         <code>TorrentFile</code> and its info hash is the same as this
 	 *         one, <code>false</code> otherwise
 	 */
 	public boolean equals(Object other) {
 		if (this == other) {
 			return true;
 		} else if (other instanceof TorrentFile) {
 			return infoHash.equals(((TorrentFile) other).infoHash);
 		} else {
 			return false;
 		}
 	}

 	/**
 	 * Returns the hash code of this <code>TorrentFile</code> based on its
 	 * info hash.
 	 *
 	 * @return the result of calling <code>hashCode()</code> on the returned
 	 *         string from {@link #getInfoHash()}
 	 */
 	public int hashCode() {
 		return infoHash.hashCode();
 	}

 }
	/*******************************************************************************
	* Copyright (c) 2006, 2008 Remy Suen, Composent Inc., and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* Remy Suen <remy.suen@gmail.com> - initial API and implementation
	******************************************************************************/
	package org.eclipse.ecf.protocol.bittorrent;

	import java.io.File;
	import java.io.FileInputStream;
	import java.io.FileNotFoundException;
	import java.io.FileOutputStream;
	import java.io.IOException;
	import java.nio.ByteBuffer;
	import java.nio.channels.FileChannel;
	import java.security.MessageDigest;
	import java.security.NoSuchAlgorithmException;
	import java.util.List;

	import org.eclipse.ecf.protocol.bittorrent.internal.encode.BEncodedDictionary;
	import org.eclipse.ecf.protocol.bittorrent.internal.encode.Decode;

	/**
	* The <code>TorrentFile</code> class is a representation of the information
	* stored within a <code>.torrent</code> file. Files can be set with the
	* {@link #setTargetFile(File)} method and then have its integrity checked
	* against the torrent's hash sum values {@link #validate()} method.
	*/
	public class TorrentFile {

	static MessageDigest shaDigest;

	private final String[] filenames;

	/**
	* An array of Strings that corresponds to the SHA-1 hash of each piece.
	*/
	private final String[] pieces;

	private final long[] lengths;

	private final byte[] torrentData;

	private final ByteBuffer buffer;

	private final BEncodedDictionary dictionary;

	private final String tracker;

	private final String infoHash;

	private final String hexHash;

	private File file;

	private String name;

	private long total;

	private final int pieceLength;

	private final int numPieces;

	static {
	try {
	shaDigest = MessageDigest.getInstance("SHA-1"); //$NON-NLS-1$
	} catch (final NoSuchAlgorithmException e) {
	throw new RuntimeException(e);
	}
	}

	/**
	* Creates a new <code>Torrent</code> to analyze the provided torrent
	* file.
	*
	* @param file
	* the torrent file
	* @throws IllegalArgumentException
	* If <code>file</code> is <code>null</code> or a directory
	* @throws IOException
	* If an I/O error occurs whilst analyzing the torrent file
	*/
	public TorrentFile(File file) throws IllegalArgumentException, IOException {
	if (file == null) {
	throw new IllegalArgumentException("The file cannot be null"); //$NON-NLS-1$
	} else if (file.isDirectory()) {
	throw new IllegalArgumentException("The provided file is a directory"); //$NON-NLS-1$
	}
	name = file.getName();
	if (name.endsWith(".torrent")) { //$NON-NLS-1$
	name = name.substring(0, name.length() - 8);
	}

	dictionary = Decode.bDecode(new FileInputStream(file));
	torrentData = dictionary.toString().getBytes("ISO-8859-1"); //$NON-NLS-1$
	tracker = (String) dictionary.get("announce"); //$NON-NLS-1$
	final BEncodedDictionary info = (BEncodedDictionary) dictionary.get("info"); //$NON-NLS-1$
	final List list = (List) info.get("files"); //$NON-NLS-1$
	if (list != null) {
	filenames = new String[list.size()];
	lengths = new long[filenames.length];
	total = 0;
	for (int i = 0; i < filenames.length; i++) {
	final BEncodedDictionary aDictionary = (BEncodedDictionary) list.get(i);
	lengths[i] = ((Long) aDictionary.get("length")).longValue(); //$NON-NLS-1$
	total += lengths[i];
	final List aList = (List) aDictionary.get("path"); //$NON-NLS-1$
	final StringBuffer buffer = new StringBuffer();
	synchronized (buffer) {
	for (int j = 0; j < aList.size(); j++) {
	buffer.append(aList.get(j)).append(File.separator);
	}
	}
	filenames[i] = buffer.toString();
	}
	} else {
	lengths = new long[] {((Long) info.get("length")).longValue()}; //$NON-NLS-1$
	total = lengths[0];
	filenames = new String[] {(String) info.get("name")}; //$NON-NLS-1$
	}
	pieceLength = ((Long) info.get("piece length")).intValue(); //$NON-NLS-1$
	buffer = ByteBuffer.allocate(pieceLength);
	final String shaPieces = (String) info.get("pieces"); //$NON-NLS-1$
	pieces = new String[shaPieces.length() / 20];
	for (int i = 0; i < pieces.length; i++) {
	pieces[i] = shaPieces.substring(i * 20, i * 20 + 20);
	}
	numPieces = pieces.length;
	infoHash = new String(shaDigest.digest(info.toString().getBytes("ISO-8859-1")), "ISO-8859-1"); //$NON-NLS-1$ //$NON-NLS-2$
	final byte[] bytes = infoHash.getBytes("ISO-8859-1"); //$NON-NLS-1$
	final StringBuffer hash = new StringBuffer(40);
	for (int i = 0; i < bytes.length; i++) {
	if (-1 < bytes[i] && bytes[i] < 16) {
	hash.append('0');
	}
	hash.append(Integer.toHexString(0xff & bytes[i]));
	}
	hexHash = hash.toString();
	}

	private boolean hashCheckFile() throws FileNotFoundException, IOException {
	final int remainder = (int) (file.length() % pieceLength);
	int count = 0;
	final FileChannel channel = new FileInputStream(file).getChannel();
	while (channel.read(buffer) == pieceLength) {
	buffer.rewind();
	if (!pieces[count].equals(new String(shaDigest.digest(buffer.array()), "ISO-8859-1"))) { //$NON-NLS-1$
	return false;
	}
	count++;
	}
	buffer.rewind();
	shaDigest.update(buffer.array(), 0, remainder);
	return pieces[pieces.length - 1].equals(new String(shaDigest.digest(), "ISO-8859-1")); //$NON-NLS-1$
	}

	private boolean hashCheckFolder() throws FileNotFoundException, IOException {
	int read = 0;
	int count = 0;
	for (int i = 0; i < filenames.length; i++) {
	final File download = new File(file.getAbsolutePath(), filenames[i]);
	final FileChannel channel = new FileInputStream(download).getChannel();
	while ((read += channel.read(buffer)) == pieceLength) {
	buffer.rewind();
	if (!pieces[count].equals(new String(shaDigest.digest(buffer.array()), "ISO-8859-1"))) { //$NON-NLS-1$
	return false;
	}
	count++;
	read = 0;
	}
	}
	buffer.rewind();
	shaDigest.update(buffer.array(), 0, read);
	return pieces[pieces.length - 1].equals(new String(shaDigest.digest(), "ISO-8859-1")); //$NON-NLS-1$
	}

	/**
	* Checks the integrity of the target file or folder as set by
	* {@link #setTargetFile(File)} to determine whether its contents pass all
	* of the hash checks.
	*
	* @return <code>true</code> if and only if every hash check has been
	* passed, <code>false</code> otherwise
	* @throws FileNotFoundException
	* If one of the files associated with the torrent could not be
	* found
	* @throws IllegalStateException
	* If the target file has not been set yet with
	* {@link #setTargetFile(File)}
	* @throws IOException
	* If an I/O error occurs while reading from the files
	*/
	public boolean validate() throws IllegalStateException, IOException {
	if (file == null) {
	throw new IllegalStateException("The target file for this torrent has not yet been set"); //$NON-NLS-1$
	}
	return file.isDirectory() ? hashCheckFolder() : hashCheckFile();
	}

	/**
	* Sets the target file or folder that this torrent should download to or
	* look for the corresponding files in.
	*
	* @param file
	* the target file or folder to use, this should be a file if the
	* torrent is a single file torrent or a folder if it has
	* multiple files
	* @throws IllegalArgumentException
	* If <code>file</code> is null or if <code>file</code> is a
	* directory when this torrent is only using a single file
	*/
	public void setTargetFile(File file) throws IllegalArgumentException {
	if (file == null) {
	throw new IllegalArgumentException("The file cannot be null"); //$NON-NLS-1$
	} else if (filenames.length == 1 && file.isDirectory()) {
	throw new IllegalArgumentException("This torrent is downloading a file, the actual file should be set here and not a directory"); //$NON-NLS-1$
	}
	this.file = file;
	}

	/**
	* Returns the hash of the <code>info</code> dictionary specified by the
	* torrent's metainfo. This is primarily used for torrent identification
	* when sending messages to the tracker.
	*
	* @return the hash of the <code>info</code> dictionary within the
	* torrent's metainfo, this will likely contain binary data and will
	* not be human-readable as a result
	*/
	public String getInfoHash() {
	return infoHash;
	}

	/**
	* Returns the hexadecimal representation of the hash returned from
	* {@link #getInfoHash()}. This string is forty characters long.
	*
	* @return the hexadecimal value of <code>getInfoHash()</code>
	*/
	public String getHexHash() {
	return hexHash;
	}

	/**
	* Retrieve the specified lengths of the files contained within this
	* torrent. Every length contained within the returned array corresponds to
	* a file's name specified by {@link #getFilenames()}.
	*
	* @return an array of lengths for each of the files specified within the
	* torrent's metainfo
	*/
	public long[] getLengths() {
	return lengths;
	}

	/**
	* Returns the length of a piece.
	*
	* @return a piece's length
	*/
	public int getPieceLength() {
	return pieceLength;
	}

	/**
	* Retrieves the URL of the tracker that's handling the requests for this
	* torrent.
	*
	* @return the tracker's URL
	*/
	public String getTracker() {
	return tracker;
	}

	/**
	* Returns a string array that contains the SHA-1 hash of each of the pieces
	* defined by the torrent's metainfo.
	*
	* @return an array of strings with the SHA-1 hash for each piece of data
	*/
	public String[] getPieces() {
	return pieces;
	}

	/**
	* Returns the number of pieces associated with this torrent.
	*
	* @return the number of pieces
	*/
	public int getNumPieces() {
	return numPieces;
	}

	/**
	* Retrieves the names of all of the files' that is specified by this
	* <code>Torrent</code>. All of the files' lengths can be matched up
	* against the long value stored within the returned array from
	* {@link #getLengths()}.
	*
	* @return an array of names for all of the files specified by the metadata
	*/
	public String[] getFilenames() {
	return filenames;
	}

	/**
	* Retrieves the name of this torrent file. This is dictated by whatever is
	* before the ending <code>.torrent</code> extension. If no such extension
	* exists, the entire file's name will be returned.
	*
	* @return the name of this torrent without the trailing
	* <code>.torrent</code> extension, if present
	*/
	public String getName() {
	return name;
	}

	/**
	* Gets the file that has been set as the target file of this torrent per
	* {@link #setTargetFile(File)}.
	*
	* @return the target file for this torrent
	*/
	public File getTargetFile() {
	return file;
	}

	/**
	* Returns whether this torrent is associated with multiple files or not.
	*
	* @return <code>true</code> if this torrent specifies multiple files,
	* <code>false</code> otherwise
	*/
	public boolean isMultiFile() {
	return lengths.length != 1;
	}

	/**
	* Retrieves the total length of all of the files specified within this
	* torrent. This is equivalent to the sum of all the lengths returned from
	* the array in {@link #getLengths()}.
	*
	* @return the combined length of all the files specified by this torrent
	*/
	public long getTotalLength() {
	return total;
	}

	/**
	* Writes the contents of the file that was used to initialize this
	* <code>TorrentFile</code> onto the provided file.
	*
	* @param file
	* the file to save to
	* @throws IOException
	* If an I/O error occurs while trying to write to the file
	*/
	public void save(File file) throws IOException {
	final FileOutputStream fos = new FileOutputStream(file);
	fos.write(torrentData);
	fos.flush();
	fos.close();
	}

	/**
	* Returns whether this <code>TorrentFile</code> is equal to the given
	* object. The two are the same if their info hash section of the contained
	* metainfo is the same. If <code>other</code> is not an instance of a
	* <code>TorrentFile</code>, <code>false</code> is returned.
	* @param other
	*
	* @return <code>true</code> if <code>other</code> is a
	* <code>TorrentFile</code> and its info hash is the same as this
	* one, <code>false</code> otherwise
	*/
	public boolean equals(Object other) {
	if (this == other) {
	return true;
	} else if (other instanceof TorrentFile) {
	return infoHash.equals(((TorrentFile) other).infoHash);
	} else {
	return false;
	}
	}

	/**
	* Returns the hash code of this <code>TorrentFile</code> based on its
	* info hash.
	*
	* @return the result of calling <code>hashCode()</code> on the returned
	* string from {@link #getInfoHash()}
	*/
	public int hashCode() {
	return infoHash.hashCode();
	}

	}