Add sACN universe discovery announcements

sacn/sender.go

@@ -3,18 +3,21 @@ package sacn
 import (
 	"crypto/rand"
 	"net"
+	"sort"
 	"sync"
+	"time"
 
 	"golang.org/x/net/ipv4"
 )
 
-// Sender sends sACN (E1.31) packets
 type Sender struct {
 	conn       *net.UDPConn
 	sourceName string
 	cid        [16]byte
 	sequences  map[uint16]uint8
 	seqMu      sync.Mutex
+	universes  map[uint16]bool
+	done       chan struct{}
 }
 
 // NewSender creates a new sACN sender
@@ -45,6 +48,8 @@ func NewSender(sourceName string, ifaceName string) (*Sender, error) {
 		sourceName: sourceName,
 		cid:        cid,
 		sequences:  make(map[uint16]uint8),
+		universes:  make(map[uint16]bool),
+		done:       make(chan struct{}),
 	}, nil
 }
 
@@ -75,7 +80,65 @@ func (s *Sender) SendDMXUnicast(addr *net.UDPAddr, universe uint16, data []byte)
 	return err
 }
 
-// Close closes the sender
 func (s *Sender) Close() error {
+	select {
+	case <-s.done:
+	default:
+		close(s.done)
+	}
 	return s.conn.Close()
 }
+
+func (s *Sender) RegisterUniverse(universe uint16) {
+	s.seqMu.Lock()
+	s.universes[universe] = true
+	s.seqMu.Unlock()
+}
+
+func (s *Sender) StartDiscovery() {
+	go s.discoveryLoop()
+}
+
+func (s *Sender) discoveryLoop() {
+	ticker := time.NewTicker(10 * time.Second)
+	defer ticker.Stop()
+
+	s.sendDiscovery()
+
+	for {
+		select {
+		case <-s.done:
+			return
+		case <-ticker.C:
+			s.sendDiscovery()
+		}
+	}
+}
+
+func (s *Sender) sendDiscovery() {
+	s.seqMu.Lock()
+	universes := make([]uint16, 0, len(s.universes))
+	for u := range s.universes {
+		universes = append(universes, u)
+	}
+	s.seqMu.Unlock()
+
+	if len(universes) == 0 {
+		return
+	}
+
+	sort.Slice(universes, func(i, j int) bool { return universes[i] < universes[j] })
+
+	const maxPerPage = 512
+	totalPages := (len(universes) + maxPerPage - 1) / maxPerPage
+
+	for page := 0; page < totalPages; page++ {
+		start := page * maxPerPage
+		end := start + maxPerPage
+		if end > len(universes) {
+			end = len(universes)
+		}
+		pkt := BuildDiscoveryPacket(s.sourceName, s.cid, uint8(page), uint8(totalPages-1), universes[start:end])
+		s.conn.WriteToUDP(pkt, DiscoveryAddr)
+	}
+}