84 lines
2.0 KiB
Go
84 lines
2.0 KiB
Go
package torrent
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import (
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"errors"
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"github.com/anacrolix/torrent/metainfo"
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pp "github.com/anacrolix/torrent/peer_protocol"
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)
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type chunkSpec struct {
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Begin, Length pp.Integer
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}
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type request struct {
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Index pp.Integer
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chunkSpec
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}
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func newRequest(index, begin, length pp.Integer) request {
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return request{index, chunkSpec{begin, length}}
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}
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// The size in bytes of a metadata extension piece.
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func metadataPieceSize(totalSize int, piece int) int {
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ret := totalSize - piece*(1<<14)
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if ret > 1<<14 {
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ret = 1 << 14
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}
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return ret
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}
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// Return the request that would include the given offset into the torrent data.
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func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) (
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r request, ok bool) {
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if offset < 0 || offset >= torrentLength {
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return
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}
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r.Index = pp.Integer(offset / pieceSize)
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r.Begin = pp.Integer(offset % pieceSize / chunkSize * chunkSize)
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r.Length = pp.Integer(chunkSize)
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pieceLeft := pp.Integer(pieceSize - int64(r.Begin))
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if r.Length > pieceLeft {
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r.Length = pieceLeft
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}
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torrentLeft := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin)
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if int64(r.Length) > torrentLeft {
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r.Length = pp.Integer(torrentLeft)
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}
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ok = true
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return
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}
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func torrentRequestOffset(torrentLength, pieceSize int64, r request) (off int64) {
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off = int64(r.Index)*pieceSize + int64(r.Begin)
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if off < 0 || off >= torrentLength {
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panic("invalid request")
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}
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return
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}
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func validateInfo(info *metainfo.Info) error {
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if len(info.Pieces)%20 != 0 {
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return errors.New("pieces has invalid length")
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}
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if info.PieceLength == 0 {
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if info.TotalLength() != 0 {
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return errors.New("zero piece length")
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}
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} else {
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if int((info.TotalLength()+info.PieceLength-1)/info.PieceLength) != info.NumPieces() {
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return errors.New("piece count and file lengths are at odds")
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}
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}
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return nil
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}
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func chunkIndexSpec(index int, pieceLength, chunkSize pp.Integer) chunkSpec {
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ret := chunkSpec{pp.Integer(index) * chunkSize, chunkSize}
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if ret.Begin+ret.Length > pieceLength {
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ret.Length = pieceLength - ret.Begin
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}
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return ret
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}
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