adding README and torrent file bits

torrent/file.go

@@ -0,0 +1,114 @@
+package torrent
+
+import (
+	//"github.com/vbatts/go-bt/bencode"
+	"crypto/sha1"
+)
+
+/*
+map[string]interface {}{"announce":"http://torrent.fedoraproject.org:6969/announce", "creation date":1387244350, "info":map[string]interface {}{"files":[]interface {}{map[string]interface {}{"length":1125, "path":[]interface {}{"Fedora-20-x86_64-CHECKSUM"}}, map[string]interface {}{"length":4603248640, "path":[]interface {}{"Fedora-20-x86_64-DVD.iso"}}}, "name":"Fedora-20-x86_64-DVD", "piece length":262144, "pieces":"m\x
+*/
+type File struct {
+	// URL of a main tracker
+	Announce string "announce"
+
+	// Epoch of the creation of this torrent
+	CreationDate int64 "creation date"
+
+	// Dictionary about this torrent, including files to be tracked
+	Info TorrentFileInfo "info"
+}
+
+type TorrentFileInfo struct {
+	// suggested file/directory name where the file(s) are to be saved
+	Name string "name"
+
+	// hash list of joined SHA1 sums (160-bit length)
+	Pieces string "pieces"
+
+	// number of bytes per piece
+	PieceLength int64 "piece length"
+
+	// size of the file in bytes (only if this torrent is for a single file)
+	Length int64 "length"
+
+	// list of information about the files
+	Files []FileInfo "files"
+}
+
+func (tfi TorrentFileInfo) PiecesList() []string {
+	pieces := []string{}
+	for i := 0; i < (len(tfi.Pieces) / sha1.Size); i++ {
+		pieces = append(pieces, tfi.Pieces[i*sha1.Size:(i+1)*sha1.Size])
+	}
+	return pieces
+}
+
+type FileInfo struct {
+	// size of file in bytes
+	Length int64 "length"
+
+	// list of strings corresponding to subdirectory names, the last of which is the actual file name
+	Path []string "path"
+}
+
+type torrentError struct {
+  Msg string
+}
+func (te torrentError) Error() string {
+  return te.Msg
+}
+
+var (
+  ErrNotProperDataInterface = torrentError{"data does not look like map[string]interface{}"}
+)
+
+func DecocdeTorrentData(data interface{}) (*File, error) {
+	m, ok := data.(map[string]interface{})
+	if !ok {
+		return nil, ErrNotProperDataInterface
+	}
+	announce := m["announce"].(string)
+	creationDate := m["creation date"].(int64)
+
+	info := m["info"].(map[string]interface{})
+	pieceLength := info["piece length"].(int64)
+	pieces := info["pieces"].(string)
+	infoName := info["name"].(string)
+
+	isSingleFileTorrent := true
+	infoFiles, ok := info["files"].([]interface{})
+	if ok {
+		isSingleFileTorrent = false
+	}
+	infoLength := int64(0)
+	if isSingleFileTorrent {
+		infoLength = info["length"].(int64)
+	}
+	files := []FileInfo{}
+	if !isSingleFileTorrent {
+		for _, fileInterface := range infoFiles {
+			fileInfo := fileInterface.(map[string]interface{})
+			paths := []string{}
+			for _, path := range fileInfo["path"].([]interface{}) {
+				paths = append(paths, path.(string))
+			}
+			files = append(files, FileInfo{
+				Length: fileInfo["length"].(int64),
+				Path:   paths,
+			})
+		}
+	}
+
+	return &File{
+		Announce:     announce,
+		CreationDate: creationDate,
+		Info: TorrentFileInfo{
+			Name:        infoName,
+			Length:      infoLength,
+			Pieces:      pieces,
+			PieceLength: pieceLength,
+			Files:       files,
+		},
+	}, nil
+}