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metainfo.go
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metainfo.go
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package metainfo
import (
"crypto/sha1"
"errors"
"fmt"
"io"
"log"
"os"
"path/filepath"
"strings"
"time"
"github.com/anacrolix/torrent/bencode"
)
// Information specific to a single file inside the MetaInfo structure.
type FileInfo struct {
Length int64 `bencode:"length"`
Path []string `bencode:"path"`
}
// Load a MetaInfo from an io.Reader. Returns a non-nil error in case of
// failure.
func Load(r io.Reader) (*MetaInfo, error) {
var mi MetaInfo
d := bencode.NewDecoder(r)
err := d.Decode(&mi)
if err != nil {
return nil, err
}
return &mi, nil
}
// Convenience function for loading a MetaInfo from a file.
func LoadFromFile(filename string) (*MetaInfo, error) {
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer f.Close()
return Load(f)
}
// The info dictionary.
type Info struct {
PieceLength int64 `bencode:"piece length"`
Pieces []byte `bencode:"pieces"`
Name string `bencode:"name"`
Length int64 `bencode:"length,omitempty"`
Private bool `bencode:"private,omitempty"`
Files []FileInfo `bencode:"files,omitempty"`
}
func (info *Info) BuildFromFilePath(root string) (err error) {
info.Name = filepath.Base(root)
info.Files = nil
err = filepath.Walk(root, func(path string, fi os.FileInfo, err error) error {
log.Println(path, root, err)
if fi.IsDir() {
// Directories are implicit in torrent files.
return nil
} else if path == root {
// The root is a file.
info.Length = fi.Size()
return nil
}
relPath, err := filepath.Rel(root, path)
log.Println(relPath, err)
if err != nil {
return fmt.Errorf("error getting relative path: %s", err)
}
info.Files = append(info.Files, FileInfo{
Path: strings.Split(relPath, string(filepath.Separator)),
Length: fi.Size(),
})
return nil
})
if err != nil {
return
}
err = info.GeneratePieces(func(fi FileInfo) (io.ReadCloser, error) {
return os.Open(filepath.Join(root, strings.Join(fi.Path, string(filepath.Separator))))
})
if err != nil {
err = fmt.Errorf("error generating pieces: %s", err)
}
return
}
func (info *Info) writeFiles(w io.Writer, open func(fi FileInfo) (io.ReadCloser, error)) error {
for _, fi := range info.UpvertedFiles() {
r, err := open(fi)
if err != nil {
return fmt.Errorf("error opening %s: %s", fi, err)
}
wn, err := io.CopyN(w, r, fi.Length)
r.Close()
if wn != fi.Length || err != nil {
return fmt.Errorf("error hashing %s: %s", fi, err)
}
}
return nil
}
// Set info.Pieces by hashing info.Files.
func (info *Info) GeneratePieces(open func(fi FileInfo) (io.ReadCloser, error)) error {
if info.PieceLength == 0 {
return errors.New("piece length must be non-zero")
}
pr, pw := io.Pipe()
go func() {
err := info.writeFiles(pw, open)
pw.CloseWithError(err)
}()
defer pr.Close()
var pieces []byte
for {
hasher := sha1.New()
wn, err := io.CopyN(hasher, pr, info.PieceLength)
if err == io.EOF {
err = nil
}
if err != nil {
return err
}
if wn == 0 {
break
}
pieces = hasher.Sum(pieces)
if wn < info.PieceLength {
break
}
}
info.Pieces = pieces
return nil
}
func (me *Info) TotalLength() (ret int64) {
if me.IsDir() {
for _, fi := range me.Files {
ret += fi.Length
}
} else {
ret = me.Length
}
return
}
func (me *Info) NumPieces() int {
if len(me.Pieces)%20 != 0 {
panic(len(me.Pieces))
}
return len(me.Pieces) / 20
}
type Piece struct {
Info *Info
i int
}
func (me Piece) Length() int64 {
if me.i == me.Info.NumPieces()-1 {
return me.Info.TotalLength() - int64(me.i)*me.Info.PieceLength
}
return me.Info.PieceLength
}
func (me Piece) Offset() int64 {
return int64(me.i) * me.Info.PieceLength
}
func (me Piece) Hash() []byte {
return me.Info.Pieces[me.i*20 : (me.i+1)*20]
}
func (me *Info) Piece(i int) Piece {
return Piece{me, i}
}
func (i *Info) IsDir() bool {
return len(i.Files) != 0
}
// The files field, converted up from the old single-file in the parent info
// dict if necessary. This is a helper to avoid having to conditionally handle
// single and multi-file torrent infos.
func (i *Info) UpvertedFiles() []FileInfo {
if len(i.Files) == 0 {
return []FileInfo{{
Length: i.Length,
// Callers should determine that Info.Name is the basename, and
// thus a regular file.
Path: nil,
}}
}
return i.Files
}
// The info dictionary with its hash and raw bytes exposed, as these are
// important to Bittorrent.
type InfoEx struct {
Info
Hash []byte
Bytes []byte
}
var (
_ bencode.Marshaler = InfoEx{}
_ bencode.Unmarshaler = &InfoEx{}
)
func (this *InfoEx) UnmarshalBencode(data []byte) error {
this.Bytes = make([]byte, 0, len(data))
this.Bytes = append(this.Bytes, data...)
h := sha1.New()
_, err := h.Write(this.Bytes)
if err != nil {
panic(err)
}
this.Hash = h.Sum(nil)
return bencode.Unmarshal(data, &this.Info)
}
func (this InfoEx) MarshalBencode() ([]byte, error) {
if this.Bytes != nil {
return this.Bytes, nil
}
return bencode.Marshal(&this.Info)
}
type MetaInfo struct {
Info InfoEx `bencode:"info"`
Announce string `bencode:"announce,omitempty"`
AnnounceList [][]string `bencode:"announce-list,omitempty"`
Nodes [][]string `bencode:"nodes,omitempty"`
CreationDate int64 `bencode:"creation date,omitempty"`
Comment string `bencode:"comment,omitempty"`
CreatedBy string `bencode:"created by,omitempty"`
Encoding string `bencode:"encoding,omitempty"`
URLList interface{} `bencode:"url-list,omitempty"`
}
// Encode to bencoded form.
func (mi *MetaInfo) Write(w io.Writer) error {
return bencode.NewEncoder(w).Encode(mi)
}
// Set good default values in preparation for creating a new MetaInfo file.
func (mi *MetaInfo) SetDefaults() {
mi.Comment = "yoloham"
mi.CreatedBy = "github.com/anacrolix/torrent"
mi.CreationDate = time.Now().Unix()
mi.Info.PieceLength = 256 * 1024
}