add generic list type

Author: paulwe

utils/list/list.go

@@ -0,0 +1,124 @@
+package list
+
+type Hook[T any] struct {
+	next *T
+	prev *T
+}
+
+func (h *Hook[T]) getListHook() *Hook[T] {
+	return h
+}
+
+func (h *Hook[T]) Next() *T {
+	if h == nil {
+		return nil
+	}
+	return h.next
+}
+
+func (h *Hook[T]) Prev() *T {
+	if h == nil {
+		return nil
+	}
+	return h.prev
+}
+
+type hookAccessor[T any] interface {
+	getListHook() *Hook[T]
+}
+
+type Hooked[T any] interface {
+	*T
+	hookAccessor[T]
+}
+
+type List[T any, P Hooked[T]] struct {
+	head P
+	tail P
+}
+
+func (l *List[T, P]) Empty() bool {
+	return l.head == nil
+}
+
+func (l *List[T, P]) Front() P {
+	return l.head
+}
+
+func (l *List[T, P]) Back() P {
+	return l.tail
+}
+
+func (l *List[T, P]) PushFront(it P) {
+	l.insert(it, nil, l.head)
+}
+
+func (l *List[T, P]) PushBack(it P) {
+	l.insert(it, l.tail, nil)
+}
+
+func (l *List[T, P]) InsertBefore(it, mark P) {
+	l.insert(it, mark.getListHook().prev, mark)
+}
+
+func (l *List[T, P]) InsertAfter(it, mark P) {
+	l.insert(it, mark, mark.getListHook().next)
+}
+
+func (l *List[T, P]) MoveToFront(it P) {
+	if l.head == it {
+		return
+	}
+	h := it.getListHook()
+	l.unlink(h)
+	l.link(it, h, nil, l.head)
+}
+
+func (l *List[T, P]) MoveToBack(it P) {
+	if l.tail == it {
+		return
+	}
+	h := it.getListHook()
+	l.unlink(h)
+	l.link(it, h, l.tail, nil)
+}
+
+func (l *List[T, P]) Remove(it P) {
+	h := it.getListHook()
+	l.unlink(h)
+	h.next = nil
+	h.prev = nil
+}
+
+func (l *List[T, P]) insert(it, prev, next P) {
+	l.link(it, it.getListHook(), prev, next)
+}
+
+func (l *List[T, P]) link(it P, h *Hook[T], prev, next P) {
+	h.prev = prev
+	h.next = next
+
+	if prev != nil {
+		prev.getListHook().next = it
+	} else {
+		l.head = it
+	}
+	if next != nil {
+		next.getListHook().prev = it
+	} else {
+		l.tail = it
+	}
+}
+
+func (l *List[T, P]) unlink(h *Hook[T]) {
+	if h.prev != nil {
+		P(h.prev).getListHook().next = h.next
+	} else {
+		l.head = h.next
+	}
+	if h.next != nil {
+		P(h.next).getListHook().prev = h.prev
+	} else {
+		l.tail = h.prev
+	}
+}

utils/list/list_test.go

@@ -0,0 +1,80 @@
+package list
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+type testItem struct {
+	Hook[testItem]
+	value string
+}
+
+type testList = List[testItem, *testItem]
+
+func collectValues(l *testList) []string {
+	var out []string
+	for it := l.Front(); it != nil; it = it.Next() {
+		out = append(out, it.value)
+	}
+	return out
+}
+
+func TestTLZeroValue(t *testing.T) {
+	var l testList
+	require.True(t, l.Empty())
+	require.Nil(t, l.Front())
+	require.Nil(t, l.Back())
+}
+
+func TestTLPushFrontBackAndRemove(t *testing.T) {
+	var l testList
+	a := &testItem{value: "a"}
+	b := &testItem{value: "b"}
+	c := &testItem{value: "c"}
+
+	l.PushFront(b)
+	l.PushFront(a)
+	l.PushBack(c)
+
+	require.Equal(t, []string{"a", "b", "c"}, collectValues(&l))
+	require.Same(t, a, l.Front())
+	require.Same(t, c, l.Back())
+	require.Same(t, b, a.Next())
+	require.Same(t, b, c.Prev())
+
+	l.Remove(b)
+	require.Equal(t, []string{"a", "c"}, collectValues(&l))
+	require.Nil(t, b.Next())
+	require.Nil(t, b.Prev())
+
+	l.Remove(a)
+	l.Remove(c)
+	require.True(t, l.Empty())
+	require.Nil(t, l.Front())
+	require.Nil(t, l.Back())
+}
+
+func TestTLInsertAndMove(t *testing.T) {
+	var l testList
+	a := &testItem{value: "a"}
+	b := &testItem{value: "b"}
+	c := &testItem{value: "c"}
+	d := &testItem{value: "d"}
+
+	l.PushBack(a)
+	l.PushBack(c)
+	l.InsertAfter(b, a)
+	l.InsertBefore(d, a)
+
+	require.Equal(t, []string{"d", "a", "b", "c"}, collectValues(&l))
+
+	l.MoveToFront(c)
+	require.Equal(t, []string{"c", "d", "a", "b"}, collectValues(&l))
+
+	l.MoveToBack(d)
+	require.Equal(t, []string{"c", "a", "b", "d"}, collectValues(&l))
+	require.Same(t, c, l.Front())
+	require.Same(t, d, l.Back())
+}