metainfo/piece.go

   1 package metainfo
   2
   3 import (
   4         g "github.com/anacrolix/generics"
   5 )
   6
   7 type Piece struct {
   8         Info *Info // Can we embed the fields here instead, or is it something to do with saving memory?
   9         i    pieceIndex
  10 }
  11
  12 type pieceIndex = int
  13
  14 func (p Piece) Length() int64 {
  15         if p.Info.HasV2() {
  16                 var offset int64
  17                 pieceLength := p.Info.PieceLength
  18                 lastFileEnd := int64(0)
  19                 done := false
  20                 p.Info.FileTree.upvertedFiles(pieceLength, func(fi FileInfo) {
  21                         if done {
  22                                 return
  23                         }
  24                         fileStartPiece := int(offset / pieceLength)
  25                         if fileStartPiece > p.i {
  26                                 done = true
  27                                 return
  28                         }
  29                         lastFileEnd = offset + fi.Length
  30                         offset = (lastFileEnd + pieceLength - 1) / pieceLength * pieceLength
  31                 })
  32                 ret := min(lastFileEnd-int64(p.i)*pieceLength, pieceLength)
  33                 if ret <= 0 {
  34                         panic(ret)
  35                 }
  36                 return ret
  37         }
  38         return p.V1Length()
  39 }
  40
  41 func (p Piece) V1Length() int64 {
  42         i := p.i
  43         lastPiece := p.Info.NumPieces() - 1
  44         switch {
  45         case 0 <= i && i < lastPiece:
  46                 return p.Info.PieceLength
  47         case lastPiece >= 0 && i == lastPiece:
  48                 files := p.Info.UpvertedFiles()
  49                 lastFile := files[len(files)-1]
  50                 length := lastFile.TorrentOffset + lastFile.Length - int64(i)*p.Info.PieceLength
  51                 if length <= 0 || length > p.Info.PieceLength {
  52                         panic(length)
  53                 }
  54                 return length
  55         default:
  56                 panic(i)
  57         }
  58 }
  59
  60 func (p Piece) Offset() int64 {
  61         return int64(p.i) * p.Info.PieceLength
  62 }
  63
  64 func (p Piece) V1Hash() (ret g.Option[Hash]) {
  65         if !p.Info.HasV1() {
  66                 return
  67         }
  68         copy(ret.Value[:], p.Info.Pieces[p.i*HashSize:(p.i+1)*HashSize])
  69         ret.Ok = true
  70         return
  71 }
  72
  73 func (p Piece) Index() int {
  74         return p.i
  75 }