move codec-specific utilities into pkg/codecs

pkg/codecs/jpeg/start_of_scan_test.go

@@ -0,0 +1,42 @@
+package jpeg
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+var casesStartOfScan = []struct {
+	name string
+	enc  []byte
+	dec  StartOfScan
+}{
+	{
+		"base",
+		[]byte{
+			0xff, 0xda, 0x0, 0xc, 0x3, 0x0, 0x0, 0x1,
+			0x11, 0x2, 0x11, 0x0, 0x3f, 0x0,
+		},
+		StartOfScan{},
+	},
+}
+
+func TestStartOfScanUnmarshal(t *testing.T) {
+	for _, ca := range casesStartOfScan {
+		t.Run(ca.name, func(t *testing.T) {
+			var h StartOfScan
+			err := h.Unmarshal(ca.enc[4:])
+			require.NoError(t, err)
+			require.Equal(t, ca.dec, h)
+		})
+	}
+}
+
+func TestStartOfScanMarshal(t *testing.T) {
+	for _, ca := range casesStartOfScan {
+		t.Run(ca.name, func(t *testing.T) {
+			byts := ca.dec.Marshal(nil)
+			require.Equal(t, ca.enc, byts)
+		})
+	}
+}