public static TorrentMetadata ReadTorrentFile(this Stream stream)
{
stream = stream ?? throw new ArgumentNullException(nameof(stream));
try
{
var parser = new BencodeParser();
var dict = parser.Parse <BDictionary>(stream);
var torrent = new TorrentMetadata();
foreach (var item in dict)
{
var readableKey = item.Key.ToString();
if (Parsers.TryGetValue(readableKey, out Action <IBObject, TorrentMetadata> action))
{
action(item.Value, torrent);
}
else
{
torrent.Extensions.Add(readableKey, item.Value);
}
}
return(torrent);
}
catch (Exception e)
{
throw new DataMisalignedException("Torrent was not recognized", e);
}
}
private static void ExtractAnounceList(IBObject obj, TorrentMetadata file)
{
var lst = (BList)obj;
foreach (var item in lst)
{
var subList = (BList)item;
foreach (var subItem in subList)
{
file.AnnounceList.Add(new Uri(subItem.ToString()));
}
}
}
public static bool ValidatePiece(this Stream piece, int index, TorrentMetadata meta)
{
meta = meta ?? throw new ArgumentNullException(nameof(meta));
piece = piece ?? throw new ArgumentNullException(nameof(piece));
if (index < 0 || index >= meta.SHAs.Count)
{
throw new IndexOutOfRangeException(nameof(index));
}
using (var calc = SHA1.Create())
{
var chunked = new ReadonlyChunkStream(piece, meta.PieceLength);
var hash = calc.ComputeHash(chunked);
return(hash.SequenceEqual(meta.SHAs[index]));
}
}
private static void ExtractInfo(IBObject obj, TorrentMetadata file)
{
var dict = (BDictionary)obj;
bool?singleFile = null;
foreach (var item in dict)
{
var key = item.Key.ToString();
switch (key)
{
case "length":
if (singleFile == false)
{
throw new DataMisalignedException("Torrent already have key \"files\" key");
}
singleFile = true;
var fname = string.Empty;
if (dict.TryGetValue("name", out IBObject nameVal))
{
fname = ((BString)nameVal).ToString();
}
file.Files.Add(fname, (BNumber)item.Value);
break;
case "name":
break;
case "files":
if (singleFile == true)
{
throw new DataMisalignedException("Torrent already have \"length\" key");
}
singleFile = false;
var dicLst = (BList)item.Value;
foreach (var dicListItem in dicLst)
{
var sdic = (BDictionary)dicListItem;
file.Files.Add(((BString)sdic["path"]).ToString(), (BNumber)sdic["length"]);
}
break;
case "piece length":
file.PieceLength = (BNumber)item.Value;
break;
case "pieces":
var shas = (BString)item.Value;
if (shas.Value.Count % 20 > 0)
{
throw new DataMisalignedException("SHA1 hash section is invalid");
}
var arr = shas.Value.ToArray();
for (var i = 0; i < shas.Value.Count / 20; i++)
{
var chunk = new byte[20];
Array.Copy(arr, i * 20, chunk, 0, 20);
file.SHAs.Add(chunk);
}
break;
default:
file.Extensions.Add($"info.{item.Key}", item.Value);
break;
}
}
if (singleFile == null)
{
throw new DataMisalignedException("Information about torrent contents was not found");
}
}
public static Task <IEnumerable <int> > ValidateFileAsync(this Stream stream, TorrentMetadata meta)
{
stream = stream ?? throw new ArgumentNullException(nameof(stream));
meta = meta ?? throw new ArgumentNullException(nameof(meta));
return(Task.Run(() =>
{
var currentIndex = 0;
var lstIndexes = new List <int>();
while (stream.Position != stream.Length && currentIndex < meta.SHAs.Count)
{
if (stream.ValidatePiece(currentIndex, meta) == false)
{
lstIndexes.Add(currentIndex);
}
currentIndex++;
}
return (IEnumerable <int>)lstIndexes;
}));
}
