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info.go
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/
info.go
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package metainfo
import (
"crypto/sha1"
"errors"
"fmt"
"io"
"os"
"path/filepath"
"strings"
"github.com/anacrolix/missinggo/slices"
)
// 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"`
// TODO: Document this field.
Source string `bencode:"source,omitempty"`
Files []FileInfo `bencode:"files,omitempty"`
}
// This is a helper that sets Files and Pieces from a root path and its
// children.
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 {
if err != nil {
return 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)
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
}
slices.Sort(info.Files, func(l, r FileInfo) bool {
return strings.Join(l.Path, "/") < strings.Join(r.Path, "/")
})
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
}
// Concatenates all the files in the torrent into w. open is a function that
// gets at the contents of the given file.
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 %v: %s", fi, err)
}
wn, err := io.CopyN(w, r, fi.Length)
r.Close()
if wn != fi.Length {
return fmt.Errorf("error copying %v: %s", fi, err)
}
}
return nil
}
// Sets Pieces (the block of piece hashes in the Info) by using the passed
// function to get at the torrent data.
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 (info *Info) TotalLength() (ret int64) {
if info.IsDir() {
for _, fi := range info.Files {
ret += fi.Length
}
} else {
ret = info.Length
}
return
}
func (info *Info) NumPieces() int {
return len(info.Pieces) / 20
}
func (info *Info) IsDir() bool {
return len(info.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 (info *Info) UpvertedFiles() []FileInfo {
if len(info.Files) == 0 {
return []FileInfo{{
Length: info.Length,
// Callers should determine that Info.Name is the basename, and
// thus a regular file.
Path: nil,
}}
}
return info.Files
}
func (info *Info) Piece(index int) Piece {
return Piece{info, pieceIndex(index)}
}