124 lines
2.8 KiB
Go
124 lines
2.8 KiB
Go
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.
|
|
chunkSize = 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 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
|
|
}
|