feat(tmdl): add multiplexer support

pkg/tmdl/mux.go

@@ -0,0 +1,61 @@
+package tmdl
+
+import "errors"
+
+// VirtualChannelMultiplexer handles frame scheduling from multiple Virtual Channels.
+type VirtualChannelMultiplexer struct {
+	VChannels map[uint8]*VirtualChannel // Map of VCID to VirtualChannel
+	Priority  map[uint8]int             // Scheduling weight per VC
+	lastUsed  uint8                     // Tracks last scheduled VC
+}
+
+// NewMultiplexer initializes a Virtual Channel multiplexer.
+func NewMultiplexer() *VirtualChannelMultiplexer {
+	return &VirtualChannelMultiplexer{
+		VChannels: make(map[uint8]*VirtualChannel),
+		Priority:  make(map[uint8]int),
+		lastUsed:  0,
+	}
+}
+
+// AddVirtualChannel registers a Virtual Channel with a priority weight.
+func (mux *VirtualChannelMultiplexer) AddVirtualChannel(vc *VirtualChannel, priority int) {
+	mux.VChannels[vc.VCID] = vc
+	mux.Priority[vc.VCID] = priority
+}
+
+// GetNextFrame selects the next frame for transmission based on priority.
+func (mux *VirtualChannelMultiplexer) GetNextFrame() (*TMTransferFrame, error) {
+	if len(mux.VChannels) == 0 {
+		return nil, errors.New("no virtual channels available")
+	}
+
+	// Collect all VCIDs in a slice for round-robin selection
+	vcids := make([]uint8, 0, len(mux.VChannels))
+	for vcid := range mux.VChannels {
+		vcids = append(vcids, vcid)
+	}
+
+	// Find the next eligible VC with available frames
+	for i := 0; i < len(vcids); i++ {
+		mux.lastUsed = (mux.lastUsed + 1) % uint8(len(vcids)) // Round-robin selection
+		vcid := vcids[mux.lastUsed]
+		vc := mux.VChannels[vcid]
+
+		// Check if VC has frames
+		if vc.HasFrames() {
+			return vc.GetNextFrame()
+		}
+	}
+	return nil, errors.New("no frames available in any virtual channel")
+}
+
+// HasPendingFrames checks if any Virtual Channel has pending frames.
+func (mux *VirtualChannelMultiplexer) HasPendingFrames() bool {
+	for _, vc := range mux.VChannels {
+		if vc.HasFrames() {
+			return true
+		}
+	}
+	return false
+}

pkg/tmdl/mux_test.go

@@ -0,0 +1,115 @@
+package tmdl_test
+
+import (
+	"github.com/ravisuhag/astro/pkg/tmdl"
+	"testing"
+)
+
+func TestNewMultiplexer(t *testing.T) {
+	mux := tmdl.NewMultiplexer()
+
+	if len(mux.VChannels) != 0 {
+		t.Errorf("Expected VChannels length 0, got %v", len(mux.VChannels))
+	}
+
+	if len(mux.Priority) != 0 {
+		t.Errorf("Expected Priority length 0, got %v", len(mux.Priority))
+	}
+}
+
+func TestMultiplexerAddVirtualChannel(t *testing.T) {
+	mux := tmdl.NewMultiplexer()
+	vcid := uint8(0x01)
+	bufferSize := 10
+	priority := 1
+
+	vc := tmdl.NewVirtualChannel(vcid, bufferSize)
+	mux.AddVirtualChannel(vc, priority)
+
+	if len(mux.VChannels) != 1 {
+		t.Errorf("Expected VChannels length 1, got %v", len(mux.VChannels))
+	}
+
+	if mux.VChannels[vcid] != vc {
+		t.Errorf("Expected VirtualChannel %v, got %v", vc, mux.VChannels[vcid])
+	}
+
+	if mux.Priority[vcid] != priority {
+		t.Errorf("Expected Priority %v, got %v", priority, mux.Priority[vcid])
+	}
+}
+
+func TestMultiplexerGetNextFrame(t *testing.T) {
+	mux := tmdl.NewMultiplexer()
+	vcid1 := uint8(0x01)
+	vcid2 := uint8(0x02)
+	bufferSize := 10
+	priority := 1
+
+	vc1 := tmdl.NewVirtualChannel(vcid1, bufferSize)
+	vc2 := tmdl.NewVirtualChannel(vcid2, bufferSize)
+	mux.AddVirtualChannel(vc1, priority)
+	mux.AddVirtualChannel(vc2, priority)
+
+	frame1 := &tmdl.TMTransferFrame{}
+	frame2 := &tmdl.TMTransferFrame{}
+	err := vc1.AddFrame(frame1)
+	if err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+	err = vc2.AddFrame(frame2)
+	if err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	retrievedFrame, err := mux.GetNextFrame()
+
+	if err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	if retrievedFrame != frame1 && retrievedFrame != frame2 {
+		t.Errorf("Expected frame1 or frame2, got %v", retrievedFrame)
+	}
+
+	retrievedFrame, err = mux.GetNextFrame()
+	if err != nil {
+		t.Fatalf("Expected no error, got %v", err)
+	}
+
+	if retrievedFrame != frame1 && retrievedFrame != frame2 {
+		t.Errorf("Expected frame1 or frame2, got %v", retrievedFrame)
+	}
+
+	_, err = mux.GetNextFrame()
+	if err == nil {
+		t.Fatalf("Expected error, got nil")
+	}
+}
+
+func TestMultiplexerHasPendingFrames(t *testing.T) {
+	mux := tmdl.NewMultiplexer()
+	vcid := uint8(0x01)
+	bufferSize := 10
+	priority := 1
+
+	vc := tmdl.NewVirtualChannel(vcid, bufferSize)
+	mux.AddVirtualChannel(vc, priority)
+
+	if mux.HasPendingFrames() {
+		t.Errorf("Expected HasPendingFrames to be false, got true")
+	}
+
+	frame := &tmdl.TMTransferFrame{}
+	vc.AddFrame(frame)
+
+	if !mux.HasPendingFrames() {
+		t.Errorf("Expected HasPendingFrames to be true, got false")
+	}
+
+	mux.GetNextFrame()
+
+	if mux.HasPendingFrames() {
+		t.Errorf("Expected HasPendingFrames to be false, got true")
+	}
+}