Add Magnet.String()

magnet.go

@@ -16,6 +16,20 @@ type Magnet struct {
 
 const xtPrefix = "urn:btih:"
 
+func (m *Magnet) String() (ret string) {
+	// net.URL likes to assume //, and encodes ':' on us, so we do most of
+	// this manually.
+	ret = "magnet:?xt="
+	ret += xtPrefix + hex.EncodeToString(m.InfoHash[:])
+	if m.DisplayName != "" {
+		ret += "&dn=" + url.QueryEscape(m.DisplayName)
+	}
+	for _, tr := range m.Trackers {
+		ret += "&tr=" + url.QueryEscape(tr)
+	}
+	return
+}
+
 func ParseMagnetURI(uri string) (m Magnet, err error) {
 	u, err := url.Parse(uri)
 	if err != nil {

magnet_test.go

@@ -0,0 +1,23 @@
+package torrent
+
+import (
+	"encoding/hex"
+	"testing"
+)
+
+// Converting from our Magnet type to URL string.
+func TestMagnetString(t *testing.T) {
+	m := Magnet{
+		DisplayName: "Shit Movie (1985) 1337p - Eru",
+		Trackers: []string{
+			"http://http.was.great!",
+			"udp://anti.piracy.honeypot:6969",
+		},
+	}
+	hex.Decode(m.InfoHash[:], []byte("51340689c960f0778a4387aef9b4b52fd08390cd"))
+	s := m.String()
+	const e = `magnet:?xt=urn:btih:51340689c960f0778a4387aef9b4b52fd08390cd&dn=Shit+Movie+%281985%29+1337p+-+Eru&tr=http%3A%2F%2Fhttp.was.great%21&tr=udp%3A%2F%2Fanti.piracy.honeypot%3A6969`
+	if s != e {
+		t.Fatalf("\nexpected:\n\t%q\nactual\n\t%q", e, s)
+	}
+}