package torrent import ( "errors" "net" "github.com/anacrolix/torrent/metainfo" pp "github.com/anacrolix/torrent/peer_protocol" ) type chunkSpec struct { Begin, Length pp.Integer } type request struct { Index pp.Integer chunkSpec } func newRequest(index, begin, length pp.Integer) request { return request{index, chunkSpec{begin, length}} } func newRequestFromMessage(msg *pp.Message) request { switch msg.Type { case pp.Request, pp.Cancel, pp.Reject: return newRequest(msg.Index, msg.Begin, msg.Length) case pp.Piece: return newRequest(msg.Index, msg.Begin, pp.Integer(len(msg.Piece))) default: panic(msg.Type) } } // The size in bytes of a metadata extension piece. func metadataPieceSize(totalSize int, piece int) int { ret := totalSize - piece*(1<<14) if ret > 1<<14 { ret = 1 << 14 } return ret } // Return the request that would include the given offset into the torrent data. func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) ( r request, ok bool) { if offset < 0 || offset >= torrentLength { return } r.Index = pp.Integer(offset / pieceSize) r.Begin = pp.Integer(offset % pieceSize / chunkSize * chunkSize) r.Length = pp.Integer(chunkSize) pieceLeft := pp.Integer(pieceSize - int64(r.Begin)) if r.Length > pieceLeft { r.Length = pieceLeft } torrentLeft := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin) if int64(r.Length) > torrentLeft { r.Length = pp.Integer(torrentLeft) } ok = true return } func torrentRequestOffset(torrentLength, pieceSize int64, r request) (off int64) { off = int64(r.Index)*pieceSize + int64(r.Begin) if off < 0 || off >= torrentLength { panic("invalid request") } return } func validateInfo(info *metainfo.Info) error { if len(info.Pieces)%20 != 0 { return errors.New("pieces has invalid length") } if info.PieceLength == 0 { if info.TotalLength() != 0 { return errors.New("zero piece length") } } else { if int((info.TotalLength()+info.PieceLength-1)/info.PieceLength) != info.NumPieces() { return errors.New("piece count and file lengths are at odds") } } return nil } func chunkIndexSpec(index int, pieceLength, chunkSize pp.Integer) chunkSpec { ret := chunkSpec{pp.Integer(index) * chunkSize, chunkSize} if ret.Begin+ret.Length > pieceLength { ret.Length = pieceLength - ret.Begin } return ret } func connLessTrusted(l, r *connection) bool { return l.netGoodPiecesDirtied() < r.netGoodPiecesDirtied() } // Convert a net.Addr to its compact IP representation. Either 4 or 16 bytes // per "yourip" field of http://www.bittorrent.org/beps/bep_0010.html. func addrCompactIP(addr net.Addr) (string, error) { host, _, err := net.SplitHostPort(addr.String()) if err != nil { return "", err } ip := net.ParseIP(host) if v4 := ip.To4(); v4 != nil { if len(v4) != 4 { panic(v4) } return string(v4), nil } return string(ip.To16()), nil }