Fix calculation of request for torrent data offset

[btrtrc.git] / torrent.go

diff --git a/torrent.go b/torrent.go
index 19c64d2fbb0a99dc0d205f00942d65e308a9141f..5445eb97f1d221c488b7a1748a80c3175479d4d8 100644 (file)
--- a/torrent.go
+++ b/torrent.go
@@ -74,25 +74,29 @@ func (t *Torrent) piecesByPendingBytesDesc() (indices []peer_protocol.Integer) {
        return slice.Indices
 }
 
-func (t *Torrent) offsetRequest(off int64) (req Request, ok bool) {
-       req.Index = peer_protocol.Integer(off / t.MetaInfo.PieceLength)
-       if req.Index < 0 || int(req.Index) >= len(t.Pieces) {
-               return
-       }
-       off %= t.MetaInfo.PieceLength
-       pieceLeft := t.PieceLength(req.Index) - peer_protocol.Integer(off)
-       if pieceLeft <= 0 {
+// 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
        }
-       req.Begin = chunkSize * (peer_protocol.Integer(off) / chunkSize)
-       req.Length = chunkSize
-       if req.Length > pieceLeft {
-               req.Length = pieceLeft
+       r.Index = peer_protocol.Integer(offset / pieceSize)
+       r.Begin = peer_protocol.Integer(offset % pieceSize / chunkSize * chunkSize)
+       left := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin)
+       if chunkSize < left {
+               r.Length = peer_protocol.Integer(chunkSize)
+       } else {
+               r.Length = peer_protocol.Integer(left)
        }
        ok = true
        return
 }
 
+// Return the request that would include the given offset into the torrent data.
+func (t *Torrent) offsetRequest(off int64) (req Request, ok bool) {
+       return torrentOffsetRequest(t.Length(), t.MetaInfo.PieceLength, chunkSize, off)
+}
+
 func (t *Torrent) WriteChunk(piece int, begin int64, data []byte) (err error) {
        _, err = t.Data.WriteAt(data, int64(piece)*t.MetaInfo.PieceLength+begin)
        return