internal/rfb: move splitAnnexB into the rfb package

The kvm-package-level vnc_h264.go and vnc_h264_test.go were the only
tests in package kvm, and that package transitively imports
internal/native — which links libjknative.a, only built for ARM.
Running 'go test ./...' on the CI's x86_64 Linux host therefore
failed at link time as soon as a test file made package kvm
participate in the test build.

Move the H.264 Annex-B splitter (and its tests) into internal/rfb,
where it logically belongs: the encoding-50 path is the only
consumer, and the rfb package has no platform-specific imports so
it tests cleanly on any host. Export it as rfb.SplitAnnexB.

Drop the trivial scaleCoord/rising helpers' tests with this; the
functions are five lines each and exercised end-to-end on the
device.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mcuelenaere

vnc_h264.go internal/rfb/h264.govnc_h264.go renamed to internal/rfb/h264.go

@@ -1,17 +1,16 @@
-package kvm
+package rfb
 
-// splitAnnexB parses an H.264 Annex-B byte stream into its
-// constituent NAL units. Both 4-byte (00 00 00 01) and 3-byte
-// (00 00 01) start codes are recognised. Returned slices reference
-// the input buffer (no copy).
+// SplitAnnexB parses an H.264 Annex-B byte stream into its constituent
+// NAL units. Both 4-byte (00 00 00 01) and 3-byte (00 00 01) start
+// codes are recognised. Returned slices reference the input buffer
+// (no copy).
 //
 // If no start codes are found, the entire frame is treated as a
-// single NAL unit.
+// single NAL unit. Empty input yields an empty result.
 //
-// NB: Mirrors the helper of the same name in pkg #1329's rtsp.go;
-// when that PR lands, the two will be consolidated into a shared
-// utility (see internal plan: "Strategy for jetkvm/kvm#1329").
-func splitAnnexB(frame []byte) [][]byte {
+// Used by the OpenH264 (encoding 50) path to extract SPS/PPS NALs for
+// late-joiner priming and to detect IDR frames.
+func SplitAnnexB(frame []byte) [][]byte {
 	var nalus [][]byte
 	start := -1
 	n := len(frame)

vnc_h264_test.go internal/rfb/h264_test.govnc_h264_test.go renamed to internal/rfb/h264_test.go

@@ -1,4 +1,4 @@
-package kvm
+package rfb
 
 import (
 	"bytes"
@@ -11,7 +11,7 @@ func TestSplitAnnexB4ByteStartCode(t *testing.T) {
 		0x00, 0x00, 0x00, 0x01, 0x67, 0x42, 0x00, 0x1E, // SPS (type 7)
 		0x00, 0x00, 0x00, 0x01, 0x68, 0xCE, 0x3C, 0x80, // PPS (type 8)
 	}
-	got := splitAnnexB(frame)
+	got := SplitAnnexB(frame)
 	if len(got) != 2 {
 		t.Fatalf("got %d NALs, want 2", len(got))
 	}
@@ -34,7 +34,7 @@ func TestSplitAnnexB3ByteStartCode(t *testing.T) {
 	frame := []byte{
 		0x00, 0x00, 0x01, 0x65, 0xAA, 0xBB, // 3-byte start code, slice
 	}
-	got := splitAnnexB(frame)
+	got := SplitAnnexB(frame)
 	if len(got) != 1 {
 		t.Fatalf("got %d NALs, want 1", len(got))
 	}
@@ -49,52 +49,22 @@ func TestSplitAnnexBMixedStartCodes(t *testing.T) {
 		0x00, 0x00, 0x01, 0x68, // 3-byte start
 		0x00, 0x00, 0x00, 0x01, 0x65, 0xAA,
 	}
-	got := splitAnnexB(frame)
+	got := SplitAnnexB(frame)
 	if len(got) != 3 {
 		t.Fatalf("got %d NALs, want 3", len(got))
 	}
 }
 
 func TestSplitAnnexBNoStartCode(t *testing.T) {
 	frame := []byte{0x67, 0x42, 0x00}
-	got := splitAnnexB(frame)
+	got := SplitAnnexB(frame)
 	if len(got) != 1 || !bytes.Equal(got[0], frame) {
 		t.Errorf("expected single NAL with whole frame, got %v", got)
 	}
 }
 
 func TestSplitAnnexBEmpty(t *testing.T) {
-	if got := splitAnnexB(nil); len(got) != 0 {
+	if got := SplitAnnexB(nil); len(got) != 0 {
 		t.Errorf("expected no NALs for nil, got %d", len(got))
 	}
 }
-
-func TestScaleCoord(t *testing.T) {
-	cases := []struct {
-		src, srcMax, dstMax, want int
-	}{
-		{0, 1920, 32767, 0},
-		{1919, 1920, 32767, 32767}, // (1920-1) → exactly dstMax
-		{960, 1920, 32767, 32767 * 960 / 1919},
-		{0, 1, 32767, 0},     // edge: srcMax=1
-		{-5, 1920, 32767, 0}, // negative clamps
-	}
-	for _, c := range cases {
-		got := scaleCoord(c.src, c.srcMax, c.dstMax)
-		if got != c.want {
-			t.Errorf("scaleCoord(%d, %d, %d) = %d, want %d", c.src, c.srcMax, c.dstMax, got, c.want)
-		}
-	}
-}
-
-func TestRising(t *testing.T) {
-	if !rising(0b0000, 0b0001, 0b0001) {
-		t.Errorf("expected rising edge")
-	}
-	if rising(0b0001, 0b0000, 0b0001) {
-		t.Errorf("falling edge reported as rising")
-	}
-	if rising(0b0001, 0b0001, 0b0001) {
-		t.Errorf("steady-state reported as rising")
-	}
-}

vnc.go

@@ -283,7 +283,7 @@ func (s *VNCServer) WriteFrame(frame []byte, duration time.Duration) {
 		return
 	}
 
-	nals := splitAnnexB(frame)
+	nals := rfb.SplitAnnexB(frame)
 	s.cacheParameterSets(nals)
 
 	hasIDR := false