如何在Java中生成.torrent？

我整理了这段独立的Java代码，以准备一个带有单个文件的.torrent文件。

通过调用

createTorrent()

createTorrent()

hashPieces()

MessageDigest

createTorrent()

enpre*()

有关详细信息，请参见BitTorrent规范。

public class Torrent {    private static void enpreObject(Object o, OutputStream out) throws IOException {        if (o instanceof String) enpreString((String)o, out);        else if (o instanceof Map) enpreMap((Map)o, out);        else if (o instanceof byte[]) enpreBytes((byte[])o, out);        else if (o instanceof Number) enpreLong(((Number) o).longValue(), out);        else throw new Error("Unencodable type");    }    private static void enpreLong(long value, OutputStream out) throws IOException {        out.write('i');        out.write(Long.toString(value).getBytes("US-ASCII"));        out.write('e');    }    private static void enpreBytes(byte[] bytes, OutputStream out) throws IOException {        out.write(Integer.toString(bytes.length).getBytes("US-ASCII"));        out.write(':');        out.write(bytes);    }    private static void enpreString(String str, OutputStream out) throws IOException {        enpreBytes(str.getBytes("UTF-8"), out);    }    private static void enpreMap(Map<String,Object> map, OutputStream out) throws IOException{        // Sort the map. A generic enprer should sort by key bytes        SortedMap<String,Object> sortedMap = new TreeMap<String, Object>(map);        out.write('d');        for (Entry<String, Object> e : sortedMap.entrySet()) { enpreString(e.getKey(), out); enpreObject(e.getValue(), out);        }        out.write('e');    }    private static byte[] hashPieces(File file, int pieceLength) throws IOException {        MessageDigest sha1;        try { sha1 = MessageDigest.getInstance("SHA");        } catch (NoSuchAlgorithmException e) { throw new Error("SHA1 not supported");        }        InputStream in = new FileInputStream(file);        ByteArrayOutputStream pieces = new ByteArrayOutputStream();        byte[] bytes = new byte[pieceLength];        int pieceByteCount  = 0, readCount = in.read(bytes, 0, pieceLength);        while (readCount != -1) { pieceByteCount += readCount; sha1.update(bytes, 0, readCount); if (pieceByteCount == pieceLength) {     pieceByteCount = 0;     pieces.write(sha1.digest()); } readCount = in.read(bytes, 0, pieceLength-pieceByteCount);        }        in.close();        if (pieceByteCount > 0) pieces.write(sha1.digest());        return pieces.toByteArray();    }    public static void createTorrent(File file, File sharedFile, String announceURL) throws IOException {        final int pieceLength = 512*1024;        Map<String,Object> info = new HashMap<String,Object>();        info.put("name", sharedFile.getName());        info.put("length", sharedFile.length());        info.put("piece length", pieceLength);        info.put("pieces", hashPieces(sharedFile, pieceLength));        Map<String,Object> metainfo = new HashMap<String,Object>();        metainfo.put("announce", announceURL);        metainfo.put("info", info);        OutputStream out = new FileOutputStream(file);        enpreMap(metainfo, out);        out.close();    }    public static void main(String[] args) throws Exception {        createTorrent(new File("C:/x.torrent"), new File("C:/file"), "http://example.com/announce");    }}

代码编辑： 使其更紧凑，更清晰地查看方法，在适当的地方使用字符文字，使用

instanceof Number