storage/mmap.go

   1 package storage
   2
   3 import (
   4         "fmt"
   5         "io"
   6         "os"
   7         "path/filepath"
   8
   9         "github.com/anacrolix/missinggo"
  10         "github.com/edsrzf/mmap-go"
  11
  12         "github.com/anacrolix/torrent/metainfo"
  13         "github.com/anacrolix/torrent/mmap_span"
  14 )
  15
  16 type mmapStorage struct {
  17         baseDir string
  18 }
  19
  20 func NewMMap(baseDir string) Client {
  21         return &mmapStorage{
  22                 baseDir: baseDir,
  23         }
  24 }
  25
  26 func (s *mmapStorage) OpenTorrent(info *metainfo.InfoEx) (t Torrent, err error) {
  27         span, err := mMapTorrent(&info.Info, s.baseDir)
  28         t = &mmapTorrentStorage{
  29                 span: span,
  30                 pc:   pieceCompletionForDir(s.baseDir),
  31         }
  32         return
  33 }
  34
  35 type mmapTorrentStorage struct {
  36         span mmap_span.MMapSpan
  37         pc   pieceCompletion
  38 }
  39
  40 func (ts *mmapTorrentStorage) Piece(p metainfo.Piece) Piece {
  41         return mmapStoragePiece{
  42                 pc:       ts.pc,
  43                 p:        p,
  44                 ReaderAt: io.NewSectionReader(ts.span, p.Offset(), p.Length()),
  45                 WriterAt: missinggo.NewSectionWriter(ts.span, p.Offset(), p.Length()),
  46         }
  47 }
  48
  49 func (ts *mmapTorrentStorage) Close() error {
  50         ts.pc.Close()
  51         return ts.span.Close()
  52 }
  53
  54 type mmapStoragePiece struct {
  55         pc pieceCompletion
  56         p  metainfo.Piece
  57         io.ReaderAt
  58         io.WriterAt
  59 }
  60
  61 func (sp mmapStoragePiece) GetIsComplete() bool {
  62         return sp.pc.Get(sp.p)
  63 }
  64
  65 func (sp mmapStoragePiece) MarkComplete() error {
  66         sp.pc.Set(sp.p, true)
  67         return nil
  68 }
  69
  70 func mMapTorrent(md *metainfo.Info, location string) (mms mmap_span.MMapSpan, err error) {
  71         defer func() {
  72                 if err != nil {
  73                         mms.Close()
  74                 }
  75         }()
  76         for _, miFile := range md.UpvertedFiles() {
  77                 fileName := filepath.Join(append([]string{location, md.Name}, miFile.Path...)...)
  78                 err = os.MkdirAll(filepath.Dir(fileName), 0777)
  79                 if err != nil {
  80                         err = fmt.Errorf("error creating data directory %q: %s", filepath.Dir(fileName), err)
  81                         return
  82                 }
  83                 var file *os.File
  84                 file, err = os.OpenFile(fileName, os.O_CREATE|os.O_RDWR, 0666)
  85                 if err != nil {
  86                         return
  87                 }
  88                 func() {
  89                         defer file.Close()
  90                         var fi os.FileInfo
  91                         fi, err = file.Stat()
  92                         if err != nil {
  93                                 return
  94                         }
  95                         if fi.Size() < miFile.Length {
  96                                 err = file.Truncate(miFile.Length)
  97                                 if err != nil {
  98                                         return
  99                                 }
 100                         }
 101                         if miFile.Length == 0 {
 102                                 // Can't mmap() regions with length 0.
 103                                 return
 104                         }
 105                         var mMap mmap.MMap
 106                         mMap, err = mmap.MapRegion(file,
 107                                 int(miFile.Length), // Probably not great on <64 bit systems.
 108                                 mmap.RDWR, 0, 0)
 109                         if err != nil {
 110                                 err = fmt.Errorf("error mapping file %q, length %d: %s", file.Name(), miFile.Length, err)
 111                                 return
 112                         }
 113                         if int64(len(mMap)) != miFile.Length {
 114                                 panic("mmap has wrong length")
 115                         }
 116                         mms.Append(mMap)
 117                 }()
 118                 if err != nil {
 119                         return
 120                 }
 121         }
 122         return
 123 }