package torrent import ( "crypto" "errors" "fmt" "time" "github.com/anacrolix/torrent/metainfo" pp "github.com/anacrolix/torrent/peer_protocol" ) const ( pieceHash = crypto.SHA1 maxRequests = 250 // Maximum pending requests we allow peers to send us. defaultChunkSize = 0x4000 // 16KiB // Peer ID client identifier prefix. We'll update this occasionally to // reflect changes to client behaviour that other clients may depend on. // Also see `extendedHandshakeClientVersion`. bep20 = "-GT0001-" nominalDialTimeout = time.Second * 30 minDialTimeout = 5 * time.Second ) type ( InfoHash [20]byte pieceSum [20]byte ) func (ih InfoHash) AsString() string { return string(ih[:]) } func (ih InfoHash) HexString() string { return fmt.Sprintf("%x", ih[:]) } func lastChunkSpec(pieceLength, chunkSize pp.Integer) (cs chunkSpec) { cs.Begin = (pieceLength - 1) / chunkSize * chunkSize cs.Length = pieceLength - cs.Begin return } 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}} } var ( // Requested data not yet available. errDataNotReady = errors.New("data not ready") ) // 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 } type superer interface { Super() interface{} } // Returns ok if there's a parent, and it's not nil. func super(child interface{}) (parent interface{}, ok bool) { s, ok := child.(superer) if !ok { return } parent = s.Super() ok = parent != nil return } // 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 int((info.TotalLength()+info.PieceLength-1)/info.PieceLength) != info.NumPieces() { return errors.New("piece count and file lengths are at odds") } return nil }