78 lines
1.9 KiB
Go
78 lines
1.9 KiB
Go
package torrent
|
|
|
|
import (
|
|
"errors"
|
|
|
|
"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}}
|
|
}
|
|
|
|
// 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 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
|
|
}
|