private string GetAnnounceUrl(BencodedObject bencodedAnnounceObj)
{
if (bencodedAnnounceObj.Type != BencodedType.String)
{
throw new Exception("Wrong torrent file format. Torrent announce url must be a string.");
}
return(((BencodedString)bencodedAnnounceObj).Value);
}
private long GetInfoLength(BencodedObject bencodedLength)
{
if (bencodedLength.Type != BencodedType.Integer)
{
throw new Exception("Wrong torrent file format. Length should be an integer.");
}
return(((BencodedInteger)bencodedLength).Value);
}
private string GetInfoName(BencodedObject bencodedName)
{
if (bencodedName.Type != BencodedType.String)
{
throw new Exception("Wrong torrent file format. Name should be a string.");
}
return(((BencodedString)bencodedName).Value);
}
private TorrentInfoSingle GetTorrentInfo(BencodedObject bencodedTorrentInfo)
{
if (bencodedTorrentInfo.Type != BencodedType.Dictionary)
{
throw new Exception("Wrong torrent file format. Torrent info must be a dictionary.");
}
var bencodedInfoDict = (BencodedDictionary)bencodedTorrentInfo;
var infoDictionary = bencodedInfoDict.Value;
if (!infoDictionary.TryGetValue("name", out BencodedObject bencodedName))
{
throw new Exception("Wrong torrent file format. Info does not contain name information.");
}
var name = GetInfoName(bencodedName);
if (!infoDictionary.TryGetValue("piece length", out BencodedObject bencodePieceLength))
{
throw new Exception("Wrong torrent file format. Info does not contain piece length information.");
}
var pieceLength = GetInfoPieceLength(bencodePieceLength);
if (!infoDictionary.TryGetValue("length", out BencodedObject bencodeLength))
{
throw new Exception("Wrong torrent file format. Info does not contain length information. This program currently supports sinlge file mode only.");
}
var length = GetInfoLength(bencodeLength);
if (!infoDictionary.TryGetValue("pieces", out BencodedObject bencodePieces))
{
throw new Exception("Wrong torrent file format. Info does not contain length information.");
}
var pieces = GetInfoPieces(bencodePieces);
var hash = HashBencodeDictionary(bencodedInfoDict);
return(new TorrentInfoSingle(hash, pieceLength, length, pieces, name));
}
private List <string> GetInfoPieces(BencodedObject bencodedLength)
{
var result = new List <string>();
if (bencodedLength.Type != BencodedType.String)
{
throw new Exception("Wrong torrent file format. Pieces should be a string.");
}
var piecesStr = ((BencodedString)bencodedLength).Value;
if (piecesStr.Length % Constants.PieceHashLength != 0)
{
throw new Exception($"Wrong torrent file format. Each piece hash should be {Constants.PieceHashLength} bytes long.");
}
for (var i = 0; i < piecesStr.Length; i += Constants.PieceHashLength)
{
var pieceHash = piecesStr.Substring(i, Math.Min(Constants.PieceHashLength, piecesStr.Length - i));
result.Add(pieceHash);
}
return(result);
}
