christophedetroyer.torrent.TorrentParser Maven / Gradle / Ivy
package christophedetroyer.torrent;
import christophedetroyer.bencoding.Reader;
import christophedetroyer.bencoding.Utils;
import christophedetroyer.bencoding.types.*;
import java.io.File;
import java.io.IOException;
import java.text.ParseException;
import java.util.*;
/**
* Created by christophe on 17.01.15.
*/
public class TorrentParser
{
public static Torrent parseTorrent(String filePath) throws IOException
{
Reader r = new Reader(new File(filePath));
List x = r.read();
// A valid torrentfile should only return a single dictionary.
if (x.size() != 1)
throw new Error("Parsing .torrent yielded wrong number of bencoding structs.");
try
{
return parseTorrent(x.get(0));
} catch (ParseException e)
{
System.err.println("Error parsing torrent!");
}
return null;
}
private static Torrent parseTorrent(Object o) throws ParseException
{
if (o instanceof BDictionary)
{
BDictionary torrentDictionary = (BDictionary) o;
BDictionary infoDictionary = parseInfoDictionary(torrentDictionary);
Torrent t = new Torrent();
///////////////////////////////////
//// OBLIGATED FIELDS /////////////
///////////////////////////////////
t.setAnnounce(parseAnnounce(torrentDictionary));
t.setInfo_hash(Utils.SHAsum(infoDictionary.bencode()));
t.setName(parseTorrentLocation(infoDictionary));
t.setPieceLength( parsePieceLength(infoDictionary));
t.setPieces(parsePiecesHashes(infoDictionary));
t.setPiecesBlob(parsePiecesBlob(infoDictionary));
///////////////////////////////////
//// OPTIONAL FIELDS //////////////
///////////////////////////////////
t.setFileList(parseFileList(infoDictionary));
t.setComment(parseComment(torrentDictionary));
t.setCreatedBy(parseCreatorName(torrentDictionary));
t.setCreationDate(parseCreationDate(torrentDictionary));
t.setAnnounceList(parseAnnounceList(torrentDictionary));
t.setTotalSize(parseSingleFileTotalSize(infoDictionary));
// Determine if torrent is a singlefile torrent.
t.setSingleFileTorrent(null != infoDictionary.find(new BByteString("length")));
return t;
} else
{
throw new ParseException("Could not parse Object to BDictionary", 0);
}
}
/**
* @param info info dictionary
* @return length — size of the file in bytes (only when one file is being shared)
*/
private static Long parseSingleFileTotalSize(BDictionary info)
{
if (null != info.find(new BByteString("length")))
return ((BInt) info.find(new BByteString("length"))).getValue();
return null;
}
/**
* @param dictionary root dictionary of torrent
* @return info — this maps to a dictionary whose keys are dependent on whether
* one or more files are being shared.
*/
private static BDictionary parseInfoDictionary(BDictionary dictionary)
{
if (null != dictionary.find(new BByteString("info")))
return (BDictionary) dictionary.find(new BByteString("info"));
else
return null;
}
/**
* @param dictionary root dictionary of torrent
* @return creation date: (optional) the creation time of the torrent, in standard UNIX epoch format
* (integer, seconds since 1-Jan-1970 00:00:00 UTC)
*/
private static Date parseCreationDate(BDictionary dictionary)
{
if (null != dictionary.find(new BByteString("creation date")))
return new Date(Long.parseLong(dictionary.find(new BByteString("creation date")).toString()));
return null;
}
/**
* @param dictionary root dictionary of torrent
* @return created by: (optional) name and version of the program used to create the .torrent (string)
*/
private static String parseCreatorName(BDictionary dictionary)
{
if (null != dictionary.find(new BByteString("created by")))
return dictionary.find(new BByteString("created by")).toString();
return null;
}
/**
* @param dictionary root dictionary of torrent
* @return comment: (optional) free-form textual comments of the author (string)
*/
private static String parseComment(BDictionary dictionary)
{
if (null != dictionary.find(new BByteString("comment")))
return dictionary.find(new BByteString("comment")).toString();
else
return null;
}
/**
* @param info infodictionary of torrent
* @return piece length — number of bytes per piece. This is commonly 28 KiB = 256 KiB = 262,144 B.
*/
private static Long parsePieceLength(BDictionary info)
{
if (null != info.find(new BByteString("piece length")))
return ((BInt) info.find(new BByteString("piece length"))).getValue();
else
return null;
}
/**
* @param info info dictionary of torrent
* @return name — suggested filename where the file is to be saved (if one file)/suggested directory name
* where the files are to be saved (if multiple files)
*/
private static String parseTorrentLocation(BDictionary info)
{
if (null != info.find(new BByteString("name")))
return info.find(new BByteString("name")).toString();
else
return null;
}
/**
* @param dictionary root dictionary of torrent
* @return announce — the URL of the tracke
*/
private static String parseAnnounce(BDictionary dictionary)
{
if (null != dictionary.find(new BByteString("announce")))
return dictionary.find(new BByteString("announce")).toString();
else
return null;
}
/**
* @param info info dictionary of .torrent file.
* @return pieces — a hash list, i.e., a concatenation of each piece's SHA-1 hash. As SHA-1 returns a 160-bit hash,
* pieces will be a string whose length is a multiple of 160-bits.
*/
private static byte[] parsePiecesBlob(BDictionary info)
{
if (null != info.find(new BByteString("pieces")))
{
return ((BByteString) info.find(new BByteString("pieces"))).getData();
} else
{
throw new Error("Info dictionary does not contain pieces bytestring!");
}
}
/**
* @param info info dictionary of .torrent file.
* @return pieces — a hash list, i.e., a concatenation of each piece's SHA-1 hash. As SHA-1 returns a 160-bit hash,
* pieces will be a string whose length is a multiple of 160-bits.
*/
private static List parsePiecesHashes(BDictionary info)
{
if (null != info.find(new BByteString("pieces")))
{
List sha1HexRenders = new ArrayList();
byte[] piecesBlob = ((BByteString) info.find(new BByteString("pieces"))).getData();
// Split the piecesData into multiple hashes. 1 hash = 20 bytes.
if (piecesBlob.length % 20 == 0)
{
int hashCount = piecesBlob.length / 20;
for (int currHash = 0; currHash < hashCount; currHash++)
{
byte[] currHashByteBlob = Arrays.copyOfRange(piecesBlob, 20 * currHash, (20 * (currHash + 1)));
String sha1 = Utils.bytesToHex(currHashByteBlob);
sha1HexRenders.add(sha1);
}
} else
{
throw new Error("Error parsing SHA1 piece hashes. Bytecount was not a multiple of 20.");
}
return sha1HexRenders;
} else
{
throw new Error("Info dictionary does not contain pieces bytestring!");
}
}
/**
* @param info info dictionary of torrent
* @return files — a list of dictionaries each corresponding to a file (only when multiple files are being shared).
*/
private static List parseFileList(BDictionary info)
{
if (null != info.find(new BByteString("files")))
{
List fileList = new ArrayList();
BList filesBList = (BList) info.find(new BByteString("files"));
Iterator fileBDicts = filesBList.getIterator();
while (fileBDicts.hasNext())
{
Object fileObject = fileBDicts.next();
if (fileObject instanceof BDictionary)
{
BDictionary fileBDict = (BDictionary) fileObject;
BList filePaths = (BList) fileBDict.find(new BByteString("path"));
BInt fileLength = (BInt) fileBDict.find(new BByteString("length"));
// Pick out each subdirectory as a string.
List paths = new LinkedList();
Iterator filePathsIterator = filePaths.getIterator();
while (filePathsIterator.hasNext())
paths.add(filePathsIterator.next().toString());
fileList.add(new TorrentFile(fileLength.getValue(), paths));
}
}
return fileList;
}
return null;
}
/**
* @param dictionary root dictionary of torrent
* @return announce-list: (optional) this is an extention to the official specification, offering
* backwards-compatibility. (list of lists of strings).
*/
private static List parseAnnounceList(BDictionary dictionary)
{
if (null != dictionary.find(new BByteString("announce-list")))
{
List announceUrls = new LinkedList();
BList announceList = (BList) dictionary.find(new BByteString("announce-list"));
Iterator subLists = announceList.getIterator();
while (subLists.hasNext())
{
BList subList = (BList) subLists.next();
Iterator elements = subList.getIterator();
while (elements.hasNext())
{
// Assume that each element is a BByteString
BByteString tracker = (BByteString) elements.next();
announceUrls.add(tracker.toString());
}
}
return announceUrls;
} else
{
return null;
}
}
}
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