internal/uevent: kobject_action lookup

This is encoded as part of kobject uevent message headers.

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

internal/uevent/action.go

@@ -0,0 +1,74 @@
+package uevent
+
+import (
+	"strconv"
+	"syscall"
+)
+
+// KobjectAction represents enum kobject_action found in include/linux/kobject.h
+// and their corresponding string representations in lib/kobject_uevent.c.
+type KobjectAction uint32
+
+// include/linux/kobject.h
+const (
+	KOBJ_ADD KobjectAction = iota
+	KOBJ_REMOVE
+	KOBJ_CHANGE
+	KOBJ_MOVE
+	KOBJ_ONLINE
+	KOBJ_OFFLINE
+	KOBJ_BIND
+	KOBJ_UNBIND
+)
+
+// lib/kobject_uevent.c
+var kobject_actions = [...]string{
+	KOBJ_ADD:     "add",
+	KOBJ_REMOVE:  "remove",
+	KOBJ_CHANGE:  "change",
+	KOBJ_MOVE:    "move",
+	KOBJ_ONLINE:  "online",
+	KOBJ_OFFLINE: "offline",
+	KOBJ_BIND:    "bind",
+	KOBJ_UNBIND:  "unbind",
+}
+
+// Valid returns whether the value of act is defined.
+func (act KobjectAction) Valid() bool { return int(act) < len(kobject_actions) }
+
+// String returns the corresponding string sent over netlink.
+func (act KobjectAction) String() string {
+	if !act.Valid() {
+		return "unsupported kobject_action " + strconv.Itoa(int(act))
+	}
+	return kobject_actions[act]
+}
+
+func (act KobjectAction) AppendText(b []byte) ([]byte, error) {
+	if !act.Valid() {
+		return b, syscall.EINVAL
+	}
+	return append(b, act.String()...), nil
+}
+
+func (act KobjectAction) MarshalText() ([]byte, error) {
+	return act.AppendText(nil)
+}
+
+// An UnsupportedActionError describes a string representation of [KobjectAction]
+// not yet supported by this package.
+type UnsupportedActionError string
+
+func (e UnsupportedActionError) Error() string {
+	return "unsupported kobject_action " + strconv.Quote(string(e))
+}
+
+func (act *KobjectAction) UnmarshalText(data []byte) error {
+	for v, s := range kobject_actions {
+		if string(data) == s {
+			*act = KobjectAction(v)
+			return nil
+		}
+	}
+	return UnsupportedActionError(data)
+}

internal/uevent/action_test.go

@@ -0,0 +1,32 @@
+package uevent_test
+
+import (
+	"syscall"
+	"testing"
+
+	"hakurei.app/internal/uevent"
+)
+
+func TestKobjectAction(t *testing.T) {
+	t.Parallel()
+
+	adeT(t, "add", uevent.KOBJ_ADD, "add", nil, nil)
+	adeT(t, "remove", uevent.KOBJ_REMOVE, "remove", nil, nil)
+	adeT(t, "change", uevent.KOBJ_CHANGE, "change", nil, nil)
+	adeT(t, "move", uevent.KOBJ_MOVE, "move", nil, nil)
+	adeT(t, "online", uevent.KOBJ_ONLINE, "online", nil, nil)
+	adeT(t, "offline", uevent.KOBJ_OFFLINE, "offline", nil, nil)
+	adeT(t, "bind", uevent.KOBJ_BIND, "bind", nil, nil)
+	adeT(t, "unbind", uevent.KOBJ_UNBIND, "unbind", nil, nil)
+
+	adeT(t, "unsupported", uevent.KobjectAction(0xbad), "explode",
+		uevent.UnsupportedActionError("explode"), syscall.EINVAL)
+	t.Run("oob string", func(t *testing.T) {
+		t.Parallel()
+
+		const want = "unsupported kobject_action 2989"
+		if got := uevent.KobjectAction(0xbad).String(); got != want {
+			t.Errorf("String: %q, want %q", got, want)
+		}
+	})
+}

internal/uevent/uevent_test.go

@@ -0,0 +1,83 @@
+package uevent_test
+
+import (
+	"encoding"
+	"fmt"
+	"reflect"
+	"testing"
+
+	"hakurei.app/internal/uevent"
+)
+
+// adeT sets up a parallel subtest for a textual appender/decoder/encoder.
+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()
+		t.Helper()
+
+		t.Run("decode", func(t *testing.T) {
+			t.Parallel()
+			t.Helper()
+
+			var got V
+			if err := S(&got).UnmarshalText([]byte(want)); !reflect.DeepEqual(err, wantErr) {
+				t.Fatalf("UnmarshalText: error = %v, want %v", err, wantErr)
+			}
+			if wantErr != nil {
+				return
+			}
+
+			if !reflect.DeepEqual(&got, &v) {
+				t.Errorf("UnmarshalText: %#v, want %#v", got, v)
+			}
+		})
+
+		t.Run("encode", func(t *testing.T) {
+			t.Parallel()
+			t.Helper()
+
+			if got, err := S(&v).MarshalText(); !reflect.DeepEqual(err, wantErrE) {
+				t.Fatalf("MarshalText: error = %v, want %v", err, wantErrE)
+			} else if err == nil && string(got) != want {
+				t.Errorf("MarshalText: %q, want %q", string(got), want)
+			}
+			if wantErrE != nil {
+				return
+			}
+
+			if got := S(&v).String(); got != want {
+				t.Errorf("String: %q, want %q", got, want)
+			}
+		})
+	})
+}
+
+func TestErrors(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name string
+		err  error
+		want string
+	}{
+		{"UnsupportedActionError", uevent.UnsupportedActionError("explode"),
+			`unsupported kobject_action "explode"`},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			if got := tc.err.Error(); got != tc.want {
+				t.Errorf("Error: %q, want %q", got, tc.want)
+			}
+		})
+	}
+}