metainfo/piece.go

   1 package metainfo
   2
   3 type Piece struct {
   4         Info *Info // Can we embed the fields here instead, or is it something to do with saving memory?
   5         i    pieceIndex
   6 }
   7
   8 type pieceIndex = int
   9
  10 func (p Piece) Length() int64 {
  11         if p.Info.HasV2() {
  12                 var offset int64
  13                 pieceLength := p.Info.PieceLength
  14                 lastFileEnd := int64(0)
  15                 done := false
  16                 p.Info.FileTree.upvertedFiles(pieceLength, func(fi FileInfo) {
  17                         if done {
  18                                 return
  19                         }
  20                         fileStartPiece := int(offset / pieceLength)
  21                         if fileStartPiece > p.i {
  22                                 done = true
  23                                 return
  24                         }
  25                         lastFileEnd = offset + fi.Length
  26                         offset = (lastFileEnd + pieceLength - 1) / pieceLength * pieceLength
  27                 })
  28                 ret := min(lastFileEnd-int64(p.i)*pieceLength, pieceLength)
  29                 if ret <= 0 {
  30                         panic(ret)
  31                 }
  32                 return ret
  33         }
  34         if p.i == p.Info.NumPieces()-1 {
  35                 return p.Info.TotalLength() - int64(p.i)*p.Info.PieceLength
  36         }
  37         return p.Info.PieceLength
  38 }
  39
  40 func (p Piece) Offset() int64 {
  41         return int64(p.i) * p.Info.PieceLength
  42 }
  43
  44 func (p Piece) Hash() (ret Hash) {
  45         copy(ret[:], p.Info.Pieces[p.i*HashSize:(p.i+1)*HashSize])
  46         return
  47 }
  48
  49 func (p Piece) Index() int {
  50         return p.i
  51 }