commit 896f60249033051fe531557d83031f3d0e2fa1c1
from: Oliver Lowe <o@olowe.co>
date: Fri Jul  4 11:28:03 2025 UTC

sdp: use encoding.TextMarshaler for Session encoding

fmt.Stringer is not really meant for larger multi-line text.
It sucks a bit that we may return an error, but this lets us
put some validation logic in; we don't have any validation yet.

commit - 035ab79449be5db836ae24e00d8bfe3317f14ea5
commit + 896f60249033051fe531557d83031f3d0e2fa1c1
blob - 5313912265ce515dae4646ee4ad514b2c8b77bf3
blob + b4570814a71b65d43f6f3cee77e4a6db39e7cd73
--- sdp/encode.go
+++ sdp/encode.go
@@ -1,21 +1,21 @@
 package sdp
 
 import (
+	"bytes"
 	"fmt"
 	"strings"
 )
 
-func (s Session) String() string {
+func (s Session) MarshalText() ([]byte, error) {
 	buf := &strings.Builder{}
 	fmt.Fprintln(buf, "v=0")
+
 	if s.Origin.Username == "" {
 		s.Origin.Username = NoUsername
 	}
-	ipv := "IP6"
-	if s.Origin.Address.Is4() {
-		ipv = "IP4"
-	}
-	fmt.Fprintf(buf, "o=%s %d %d IN %s %s\n", s.Origin.Username, s.Origin.ID, s.Origin.Version, ipv, s.Origin.Address)
+
+	fmt.Fprintln(buf, s.Origin)
+
 	fmt.Fprintf(buf, "s=%s\n", s.Name)
 
 	if s.Info != "" {
@@ -65,5 +65,5 @@ func (s Session) String() string {
 		fmt.Fprintln(buf, m)
 	}
 
-	return strings.TrimSpace(buf.String())
+	return bytes.TrimSpace([]byte(buf.String())), nil
 }
blob - d10ffc423a447ce6efdde01f4ab25e59de6225a4
blob + 913d63f5e7abd39ee8edc4b0886360022651c06f
--- sdp/encode_test.go
+++ sdp/encode_test.go
@@ -12,18 +12,21 @@ func TestWriteSession(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	b, err := io.ReadAll(f)
+	want, err := io.ReadAll(f)
 	if err != nil {
 		t.Fatal(err)
 	}
-	want := string(b)
-	session, err := ReadSession(bytes.NewReader(b))
+	session, err := ReadSession(bytes.NewReader(want))
 	if err != nil {
 		t.Fatal(err)
 	}
-	if want != session.String() {
+	got, err := session.MarshalText()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(want, got) {
 		t.Errorf("mismatched sdp text")
-		t.Log("want", want)
-		t.Log("got", session.String())
+		t.Log("want", string(want))
+		t.Log("got", string(got))
 	}
 }
blob - a2f6d52965ac0aa8362e39972003ca2ce9e7d658
blob + d20edbe5e9f6f46e74631c9cc31a88cfcd21d4b5
--- sdp/example_test.go
+++ sdp/example_test.go
@@ -12,8 +12,8 @@ import (
 // audio in RTP starts by setting the mandatory fields Origin and Name.
 // The Media field contains information about the audio such as the sample rate
 // and the number of audio channels.
-// The Session type implements fmt.Stringer;
-// to encode a Session in the SDP text format, use Session.String().
+// Session implements encoding.TextMarshaler;
+// to encode a Session in the SDP text format, use Session.MarshalText().
 func Example() {
 	session := sdp.Session{
 		Origin: sdp.Origin{
@@ -35,7 +35,8 @@ func Example() {
 			},
 		},
 	}
-	fmt.Printf("%s", session)
+	text, _ := session.MarshalText()
+	fmt.Printf("%s", text)
 	// Output:
 	// v=0
 	// o=- 3930287268 3930287268 IN IP6 2001:db8::1
blob - 6031e234406a2f1fae937eec38a27f50b6436e6e
blob + 8c78e45e3f32c9bfa9527df8f3d3377919b99f85
--- sdp/sdp.go
+++ sdp/sdp.go
@@ -60,6 +60,14 @@ type Origin struct {
 	Address netip.Addr
 }
 
+func (o Origin) String() string {
+	ipv := "IP6"
+	if o.Address.Is4() {
+		ipv = "IP4"
+	}
+	return fmt.Sprintf("o=%s %d %d IN %s %s", o.Username, o.ID, o.Version, ipv, o.Address)
+}
+
 func ReadSession(rd io.Reader) (*Session, error) {
 	parser := &parser{Scanner: bufio.NewScanner(rd)}
 	if err := parser.parse(); err != nil {