add torrent support

This change adds an option to download files with BitTorrent. A webseed
is provided in the torrent file to bootstrap the swarm.

server.go

@@ -68,6 +68,7 @@ func setup() {
 	nameRe := regexp.MustCompile(`^/(?P<name>[a-z0-9-\.]+)$`)
 	selifRe := regexp.MustCompile(`^/selif/(?P<name>[a-z0-9-\.]+)$`)
 	selifIndexRe := regexp.MustCompile(`^/selif/$`)
+	torrentRe := regexp.MustCompile(`^/(?P<name>[a-z0-9-\.]+)/torrent$`)
 
 	goji.Get("/", indexHandler)
 
@@ -83,6 +84,7 @@ func setup() {
 	goji.Get(nameRe, fileDisplayHandler)
 	goji.Get(selifRe, fileServeHandler)
 	goji.Get(selifIndexRe, unauthorizedHandler)
+	goji.Get(torrentRe, fileTorrentHandler)
 	goji.NotFound(notFoundHandler)
 }
 

server_test.go

@@ -371,6 +371,15 @@ func TestPutAndDelete(t *testing.T) {
 	if w.Code != 404 {
 		t.Fatal("Status code was not 404, but " + strconv.Itoa(w.Code))
 	}
+
+	// Make sure torrent is also gone
+	w = httptest.NewRecorder()
+	req, err = http.NewRequest("GET", "/"+myjson.Filename+"/torrent", nil)
+	goji.DefaultMux.ServeHTTP(w, req)
+
+	if w.Code != 404 {
+		t.Fatal("Status code was not 404, but " + strconv.Itoa(w.Code))
+	}
 }
 
 func TestPutAndSpecificDelete(t *testing.T) {
@@ -418,6 +427,15 @@ func TestPutAndSpecificDelete(t *testing.T) {
 	if w.Code != 404 {
 		t.Fatal("Status code was not 404, but " + strconv.Itoa(w.Code))
 	}
+
+	// Make sure torrent is gone too
+	w = httptest.NewRecorder()
+	req, err = http.NewRequest("GET", "/"+myjson.Filename+"/torrent", nil)
+	goji.DefaultMux.ServeHTTP(w, req)
+
+	if w.Code != 404 {
+		t.Fatal("Status code was not 404, but " + strconv.Itoa(w.Code))
+	}
 }
 
 func TestShutdown(t *testing.T) {

templates/display/base.html

@@ -13,6 +13,7 @@
         {% block infoleft %}{% endblock %}
 
         <div class="right">
+            <a href="{{ filename }}/torrent" download>torrent</a> |
             <a href="/selif/{{ filename }}" download>get</a>
         </div>
         <div class="clear"></div>

torrent.go

@@ -0,0 +1,96 @@
+package main
+
+import (
+	"bytes"
+	"crypto/sha1"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path"
+	"time"
+
+	"github.com/zeebo/bencode"
+	"github.com/zenazn/goji/web"
+)
+
+const (
+	TORRENT_PIECE_LENGTH = 262144
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+type TorrentInfo struct {
+	PieceLength int    `bencode:"piece length"`
+	Pieces      []byte `bencode:"pieces"`
+	Name        string `bencode:"name"`
+	Length      int    `bencode:"length"`
+}
+
+type Torrent struct {
+	Encoding string      `bencode:"encoding"`
+	Info     TorrentInfo `bencode:"info"`
+	UrlList  []string    `bencode:"url-list"`
+}
+
+func CreateTorrent(fileName string, filePath string) []byte {
+	chunk := make([]byte, TORRENT_PIECE_LENGTH)
+	var pieces []byte
+	length := 0
+
+	f, err := os.Open(filePath)
+	check(err)
+
+	for {
+		n, err := f.Read(chunk)
+		if err == io.EOF {
+			break
+		}
+		check(err)
+
+		length += n
+
+		h := sha1.New()
+		h.Write(chunk)
+		pieces = append(pieces, h.Sum(nil)...)
+	}
+
+	f.Close()
+
+	torrent := &Torrent{
+		Encoding: "UTF-8",
+		Info: TorrentInfo{
+			PieceLength: TORRENT_PIECE_LENGTH,
+			Pieces:      pieces,
+			Name:        fileName,
+			Length:      length,
+		},
+		UrlList: []string{fmt.Sprintf("%sselif/%s", Config.siteURL, fileName)},
+	}
+
+	data, err := bencode.EncodeBytes(torrent)
+	check(err)
+
+	return data
+}
+
+func fileTorrentHandler(c web.C, w http.ResponseWriter, r *http.Request) {
+	fileName := c.URLParams["name"]
+	filePath := path.Join(Config.filesDir, fileName)
+
+	if !fileExistsAndNotExpired(fileName) {
+		notFoundHandler(c, w, r)
+		return
+	}
+
+	encoded := CreateTorrent(fileName, filePath)
+
+	w.Header().Set(`Content-Disposition`, fmt.Sprintf(`attachment; filename="%s.torrent"`, fileName))
+	http.ServeContent(w, r, "", time.Now(), bytes.NewReader(encoded))
+}
+
+// vim:set ts=8 sw=8 noet:

torrent_test.go

@@ -0,0 +1,43 @@
+package main
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/zeebo/bencode"
+)
+
+func TestCreateTorrent(t *testing.T) {
+	fileName := "server.go"
+	encoded := CreateTorrent(fileName, fileName)
+	var decoded Torrent
+
+	bencode.DecodeBytes(encoded, &decoded)
+
+	if decoded.Encoding != "UTF-8" {
+		t.Fatalf("Encoding was %s, expected UTF-8", decoded.Encoding)
+	}
+
+	if decoded.Info.Name != "server.go" {
+		t.Fatalf("Name was %s, expected server.go", decoded.Info.Name)
+	}
+
+	if decoded.Info.PieceLength <= 0 {
+		t.Fatal("Expected a piece length, got none")
+	}
+
+	if len(decoded.Info.Pieces) <= 0 {
+		t.Fatal("Expected at least one piece, got none")
+	}
+
+	if decoded.Info.Length <= 0 {
+		t.Fatal("Length was less than or equal to 0, expected more")
+	}
+
+	tracker := fmt.Sprintf("%sselif/%s", Config.siteURL, fileName)
+	if decoded.UrlList[0] != tracker {
+		t.Fatal("First entry in URL list was %s, expected %s", decoded.UrlList[0], tracker)
+	}
+}
+
+// vim:set ts=8 sw=8 noet: