8 "github.com/anacrolix/torrent/metainfo"
9 pp "github.com/anacrolix/torrent/peer_protocol"
13 pieceHash = crypto.SHA1
14 maxRequests = 250 // Maximum pending requests we allow peers to send us.
15 defaultChunkSize = 0x4000 // 16KiB
16 // Peer ID client identifier prefix. We'll update this occasionally to
17 // reflect changes to client behaviour that other clients may depend on.
18 // Also see `extendedHandshakeClientVersion`.
20 nominalDialTimeout = time.Second * 30
21 minDialTimeout = 5 * time.Second
24 type chunkSpec struct {
25 Begin, Length pp.Integer
33 func newRequest(index, begin, length pp.Integer) request {
34 return request{index, chunkSpec{begin, length}}
37 // The size in bytes of a metadata extension piece.
38 func metadataPieceSize(totalSize int, piece int) int {
39 ret := totalSize - piece*(1<<14)
46 type superer interface {
50 // Return the request that would include the given offset into the torrent data.
51 func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) (
53 if offset < 0 || offset >= torrentLength {
56 r.Index = pp.Integer(offset / pieceSize)
57 r.Begin = pp.Integer(offset % pieceSize / chunkSize * chunkSize)
58 r.Length = pp.Integer(chunkSize)
59 pieceLeft := pp.Integer(pieceSize - int64(r.Begin))
60 if r.Length > pieceLeft {
63 torrentLeft := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin)
64 if int64(r.Length) > torrentLeft {
65 r.Length = pp.Integer(torrentLeft)
71 func torrentRequestOffset(torrentLength, pieceSize int64, r request) (off int64) {
72 off = int64(r.Index)*pieceSize + int64(r.Begin)
73 if off < 0 || off >= torrentLength {
74 panic("invalid request")
79 func validateInfo(info *metainfo.Info) error {
80 if len(info.Pieces)%20 != 0 {
81 return errors.New("pieces has invalid length")
83 if int((info.TotalLength()+info.PieceLength-1)/info.PieceLength) != info.NumPieces() {
84 return errors.New("piece count and file lengths are at odds")
89 func chunkIndexSpec(index int, pieceLength, chunkSize pp.Integer) chunkSpec {
90 ret := chunkSpec{pp.Integer(index) * chunkSize, chunkSize}
91 if ret.Begin+ret.Length > pieceLength {
92 ret.Length = pieceLength - ret.Begin