internal/uevent: decode uevent messages

The wire format and behaviour is entirely undocumented. This is implemented by reading lib/kobject_uevent.c, with testdata collected from the internal/rosa kernel.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/uevent/uevent_test.go

@@ -2,7 +2,6 @@ package uevent_test
 
 import (
 	"encoding"
-	"fmt"
 	"reflect"
 	"testing"
 
@@ -14,13 +13,14 @@ func adeT[V any, S interface {
 	encoding.TextAppender
 	encoding.TextMarshaler
 	encoding.TextUnmarshaler
-	fmt.Stringer
 
 	*V
 }](t *testing.T, name string, v V, want string, wantErr, wantErrE error) {
 	t.Helper()
-	t.Run(name, func(t *testing.T) {
-		t.Parallel()
+	f := func(t *testing.T) {
+		if name != "" {
+			t.Parallel()
+		}
 		t.Helper()
 
 		t.Run("decode", func(t *testing.T) {
@@ -49,15 +49,63 @@ func adeT[V any, S interface {
 			} else if err == nil && string(got) != want {
 				t.Errorf("MarshalText: %q, want %q", string(got), want)
 			}
-			if wantErrE != nil {
+		})
+	}
+	if name != "" {
+		t.Run(name, f)
+	} else {
+		f(t)
+	}
+}
+
+// adeT sets up a binary subtest for a textual appender/decoder/encoder.
+func adeB[V any, S interface {
+	encoding.BinaryAppender
+	encoding.BinaryMarshaler
+	encoding.BinaryUnmarshaler
+
+	*V
+}](t *testing.T, name string, v V, want string, wantErr, wantErrE error) {
+	t.Helper()
+	f := func(t *testing.T) {
+		if name != "" {
+			t.Parallel()
+		}
+		t.Helper()
+
+		t.Run("decode", func(t *testing.T) {
+			t.Parallel()
+			t.Helper()
+
+			var got V
+			if err := S(&got).UnmarshalBinary([]byte(want)); !reflect.DeepEqual(err, wantErr) {
+				t.Fatalf("UnmarshalBinary: error = %v, want %v", err, wantErr)
+			}
+			if wantErr != nil {
 				return
 			}
 
-			if got := S(&v).String(); got != want {
-				t.Errorf("String: %q, want %q", got, want)
+			if !reflect.DeepEqual(&got, &v) {
+				t.Errorf("UnmarshalBinary: %#v, want %#v", got, v)
 			}
 		})
-	})
+
+		t.Run("encode", func(t *testing.T) {
+			t.Parallel()
+			t.Helper()
+
+			if got, err := S(&v).MarshalBinary(); !reflect.DeepEqual(err, wantErrE) {
+				t.Fatalf("MarshalBinary: error = %v, want %v", err, wantErrE)
+			} else if err == nil && string(got) != want {
+				t.Errorf("MarshalBinary: %q, want %q", string(got), want)
+			}
+		})
+	}
+	if name != "" {
+		t.Run(name, f)
+	} else {
+		f(t)
+	}
 }
 
 func TestErrors(t *testing.T) {
@@ -70,6 +118,26 @@ func TestErrors(t *testing.T) {
 	}{
 		{"UnsupportedActionError", uevent.UnsupportedActionError("explode"),
 			`unsupported kobject_action "explode"`},
+
+		{"MissingHeaderError", uevent.MissingHeaderError("move"),
+			`message "move" has no header`},
+
+		{"MessageError MErrorKindHeaderSep", &uevent.MessageError{
+			Data:    "move\x00",
+			Section: "move",
+			Kind:    uevent.MErrorKindHeaderSep,
+		}, `header "move" missing separator`},
+
+		{"MessageError MErrorKindFinalNUL", &uevent.MessageError{
+			Data:    "move\x00truncated",
+			Section: "truncated",
+			Kind:    uevent.MErrorKindFinalNUL,
+		}, `entry "truncated" missing NUL`},
+
+		{"MessageError bad", &uevent.MessageError{
+			Data: "\x00",
+			Kind: 0xbad,
+		}, `section "" is invalid`},
 	}
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {