data/mmap/mmap.go

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