data/mmap/mmap.go

   1 package mmap
   2
   3 import (
   4         "fmt"
   5         "os"
   6         "path/filepath"
   7
   8         "github.com/anacrolix/torrent/metainfo"
   9         "launchpad.net/gommap"
  10
  11         "github.com/anacrolix/torrent/mmap_span"
  12 )
  13
  14 func TorrentData(md *metainfo.Info, location string) (mms *mmap_span.MMapSpan, err error) {
  15         mms = &mmap_span.MMapSpan{}
  16         defer func() {
  17                 if err != nil {
  18                         mms.Close()
  19                         mms = nil
  20                 }
  21         }()
  22         for _, miFile := range md.UpvertedFiles() {
  23                 fileName := filepath.Join(append([]string{location, md.Name}, miFile.Path...)...)
  24                 err = os.MkdirAll(filepath.Dir(fileName), 0777)
  25                 if err != nil {
  26                         err = fmt.Errorf("error creating data directory %q: %s", filepath.Dir(fileName), err)
  27                         return
  28                 }
  29                 var file *os.File
  30                 file, err = os.OpenFile(fileName, os.O_CREATE|os.O_RDWR, 0666)
  31                 if err != nil {
  32                         return
  33                 }
  34                 func() {
  35                         defer file.Close()
  36                         var fi os.FileInfo
  37                         fi, err = file.Stat()
  38                         if err != nil {
  39                                 return
  40                         }
  41                         if fi.Size() < miFile.Length {
  42                                 err = file.Truncate(miFile.Length)
  43                                 if err != nil {
  44                                         return
  45                                 }
  46                         }
  47                         if miFile.Length == 0 {
  48                                 // Can't mmap() regions with length 0.
  49                                 return
  50                         }
  51                         var mMap gommap.MMap
  52                         mMap, err = gommap.MapRegion(file.Fd(), 0, miFile.Length, gommap.PROT_READ|gommap.PROT_WRITE, gommap.MAP_SHARED)
  53                         if err != nil {
  54                                 err = fmt.Errorf("error mapping file %q, length %d: %s", file.Name(), miFile.Length, err)
  55                                 return
  56                         }
  57                         if int64(len(mMap)) != miFile.Length {
  58                                 panic("mmap has wrong length")
  59                         }
  60                         mms.Append(mMap)
  61                 }()
  62                 if err != nil {
  63                         return
  64                 }
  65         }
  66         return
  67 }