streaming

commit e3016940734400ce1534d0b208b08f301cb9a3b7
parent b77e66b7ee9f5346dd68fe44fd01aff3e36b1eeb
Author: Oliver Lowe <o@olowe.co>
Date:   Sat, 29 Jun 2024 22:56:49 +1000

sdp: add package for Session Description Protocol (SDP)

Incomplete. Don't know how to handle optional fields in a description
yet.

Diffstat:
A
sdp/sdp.go
 | 
132
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
sdp/sdp_test.go
 | 
31
+++++++++++++++++++++++++++++++

2 files changed, 163 insertions(+), 0 deletions(-)
diff --git a/sdp/sdp.go b/sdp/sdp.go
@@ -0,0 +1,132 @@
+// Package sdp implements a decoder and encoder for
+// Session Description Protocol formatted data as specified in
+// RFC 8866.
+package sdp
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"net/mail"
+	"net/url"
+	"strconv"
+	"strings"
+)
+
+type Session struct {
+	Version int
+	Origin  Origin
+	Name    string
+
+	Info    string
+	URI     *url.URL
+	Email   *mail.Address
+	Phone   string
+	// TODO(otl): add rest of fields
+}
+
+type Origin struct {
+	Username    string
+	ID          int
+	Version     int
+	Network     string // TODO(otl): only "IN" is valid... so int type?
+	AddressType string // TODO(otl): only "IP4", "IP6" valid... new int type?
+	Address     string
+}
+
+func ReadSession(rd io.Reader) (*Session, error) {
+	sc := bufio.NewScanner(rd)
+	next := "v"
+	var session Session
+	for sc.Scan() {
+		if sc.Text() == "" {
+			continue // TODO(otl): empty lines allowed?
+		}
+		k, v, found := strings.Cut(sc.Text(), "=")
+		if !found {
+			return nil, fmt.Errorf("parse field %q: missing %q", next, "=")
+		}
+		if k != next {
+			return nil, fmt.Errorf("expected field %q, found %q", next, k)
+		}
+		switch k {
+		case "v":
+			i, err := strconv.Atoi(v)
+			if err != nil {
+				return nil, fmt.Errorf("parse version: %w", err)
+			}
+			if i != 0 {
+				return nil, fmt.Errorf("parse version: unsupported version %d", i)
+			}
+			session.Version = i
+			next = "o"
+		case "o":
+			o, err := parseOrigin(v)
+			if err != nil {
+				return nil, fmt.Errorf("parse origin: %w", err)
+			}
+			session.Origin = o
+			next = "s"
+		case "s":
+			if v == "" {
+				return nil, fmt.Errorf("empty name")
+			}
+			session.Name = v
+		case "i":
+			session.Info = v
+			// TODO(otl): what do we expect next?
+		case "u":
+			u, err := url.Parse(v)
+			if err != nil {
+				return nil, fmt.Errorf("parse uri: %w", err)
+			}
+			session.URI = u
+			// TODO(otl): what do we expect next?
+		case "e":
+			addr, err := parseEmail(v)
+			if err != nil {
+				return nil, fmt.Errorf("parse email: %w", err)
+			}
+			session.Email = addr
+			// TODO(otl): what do we expect next?
+		default:
+			return &session, fmt.Errorf("unsupported field %q", k)
+		}
+	}
+	return &session, sc.Err()
+}
+
+func parseOrigin(line string) (Origin, error) {
+	fields := strings.Fields(line)
+	if len(fields) != 6 {
+		return Origin{}, fmt.Errorf("need %d fields but only have %d", 6, len(fields))
+	}
+	o := Origin{Username: fields[0]}
+	var err error
+	o.ID, err = strconv.Atoi(fields[1])
+	if err != nil {
+		return o, fmt.Errorf("parse session id: %w", err)
+	}
+	o.Version, err = strconv.Atoi(fields[2])
+	if err != nil {
+		return o, fmt.Errorf("parse version: %w", err)
+	}
+	o.Network = fields[3]
+	o.AddressType = fields[4]
+	o.Address = fields[5]
+	return o, nil
+}
+
+// parseEmail returns the parsed email address from s.
+// Addresses should be in RFC 5322 form, for instance
+// "Oliver Lowe <o@olowe.co>" or just "o@olowe.co".
+// They can also be in the form detailed in the SDP specification,
+// for instance
+// "Oliver Lowe (o@olowe.co)".
+func parseEmail(s string) (*mail.Address, error) {
+	// Oliver Lowe (o@olowe.co) to RFC 5322 format
+	// Oliver Lowe <o@olowe.co>
+	s = strings.ReplaceAll(s, "(", "<")
+	s = strings.ReplaceAll(s, ")", ">")
+	return mail.ParseAddress(s)
+}
diff --git a/sdp/sdp_test.go b/sdp/sdp_test.go
@@ -0,0 +1,31 @@
+package sdp
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestReadSession(t *testing.T) {
+	s := `
+v=0
+o=jdoe 3724394400 3724394405 IN IP4 198.51.100.1
+s=Call to John Smith
+i=SDP Offer #1
+u=http://www.jdoe.example.com/home.html
+e=Jane Doe <jane@jdoe.example.com>
+p=+1 617 555-6011
+c=IN IP4 198.51.100.1
+t=0 0
+m=audio 49170 RTP/AVP 0
+m=audio 49180 RTP/AVP 0
+m=video 51372 RTP/AVP 99
+c=IN IP6 2001:db8::2
+a=rtpmap:99 h263-1998/90000`
+	session, err := ReadSession(strings.NewReader(s))
+	if err != nil {
+		t.Fatalf("read session: %v", err)
+	}
+	if session.Name != "Call to John Smith" {
+		t.Errorf("bad name bla bla TODO")
+	}
+}