Play some more with torrenting

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/torrent/info.go

@@ -0,0 +1,75 @@
+package torrent
+
+import (
+	"crypto/sha1"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/zeebo/bencode"
+)
+
+const pieceLength = 2048 * 10
+
+// pieces will hash the file in path on 256kb boundaries and return the (sha1) hashes.
+func pieces(path string) (int, string, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return 0, "", err
+	}
+	hashes := "" // concatenated string of hash (strings)
+	buf := make([]byte, 2048)
+	h := sha1.New()
+	chunk := 0
+	length := 0
+	n, err := f.Read(buf)
+	for err != nil {
+		h.Write(buf[:n])
+		chunk++
+		length += n
+		if chunk > 10 {
+			chunk = 0
+			hashes += string(h.Sum(nil))
+			h = sha1.New()
+		}
+		n, err = f.Read(buf)
+	}
+	if n > 0 {
+		length += n
+		h.Write(buf[:n])
+		hashes += string(h.Sum(nil))
+	}
+
+	return length, hashes, nil
+}
+
+// Info is the torrent meta data for a single file.
+type Info struct {
+	Pieces      string `bencode:"pieces"`
+	PieceLength int    `bencode:"piece length"`
+	Length      int    `bencode:"length"`
+	Name        string `bencode:"name"`
+}
+
+// TorrentInfo contains the meta data for this torrent.
+type TorrentInfo struct {
+	Nodes []string `bencode:"nodes"`
+	Info  Info     `bencode:"info"`
+}
+
+func NewTorrentInfo(path string) (*TorrentInfo, error) {
+	length, pieces, err := pieces(path)
+	if err != nil {
+		return nil, err
+	}
+	i := Info{Pieces: pieces, PieceLength: 2048 * 10, Length: length, Name: path}
+	return &TorrentInfo{Nodes: []string{}, Info: i}, nil
+}
+
+func (t *TorrentInfo) ToReader() io.Reader {
+	s, err := bencode.EncodeString(t)
+	if err != nil {
+		return nil
+	}
+	return strings.NewReader(s)
+}