refactor: refact listpack

internal/list/bench_test.go

@@ -8,23 +8,38 @@ func BenchmarkListPack(b *testing.B) {
 	const N = 1000
 	b.Run("next", func(b *testing.B) {
 		ls := genListPack(0, N)
+		it := ls.NewIterator()
 		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
-			it := ls.NewIterator()
-			for i := 0; i < N; i++ {
-				it.Next()
-			}
+			it.SeekBegin()
+			it.Next()
 		}
 	})
 	b.Run("prev", func(b *testing.B) {
 		ls := genListPack(0, N)
+		it := ls.NewIterator()
 		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
-			it := ls.NewIterator()
 			it.SeekEnd()
-			for i := 0; i < N; i++ {
-				it.Prev()
-			}
+			it.Prev()
+		}
+	})
+	b.Run("lpush", func(b *testing.B) {
+		ls := NewListPack()
+		it := ls.NewIterator()
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			it.SeekBegin()
+			it.Insert(genKey(i))
+		}
+	})
+	b.Run("rpush", func(b *testing.B) {
+		ls := NewListPack()
+		it := ls.NewIterator()
+		b.ResetTimer()
+		for i := 0; i < b.N; i++ {
+			it.SeekEnd()
+			it.Insert(genKey(i))
 		}
 	})
 }

internal/list/listpack.go

@@ -106,16 +106,26 @@ func (it *lpIterator) Insert(data string) {
 	bpool.Put(alloc)
 }
 
-func (it *lpIterator) Remove() []byte {
+func (it *lpIterator) RemoveNext() []byte {
 	before := it.index
 	data := slices.Clone(it.Next())
 	after := it.index
 	it.data = slices.Delete(it.data, before, after)
+	it.index -= (after - before)
+	it.size--
+	return data
+}
+
+func (it *lpIterator) RemovePrev() []byte {
+	after := it.index
+	data := slices.Clone(it.Prev())
+	before := it.index
+	it.data = slices.Delete(it.data, before, after)
+	it.index -= (after - before)
 	it.size--
 	return data
 }
 
-// encode data to [data_len, data, entry_len].
 func appendEntry(dst []byte, data string) []byte {
 	if dst == nil {
 		dst = bpool.Get(maxListPackSize)[:0]

internal/list/listpack_test.go

@@ -266,13 +266,15 @@ func TestIterator(t *testing.T) {
 	data = it.Next()
 	assert.Equal(string(data), "004")
 
-	removed := it.Remove()
+	removed := it.RemoveNext()
 	assert.Equal(string(removed), "002")
 
+	removed = it.RemovePrev()
+	assert.Equal(string(removed), "004")
+
 	it.SeekEnd()
 
 	assert.Equal(string(it.Prev()), "003")
-	assert.Equal(string(it.Prev()), "004")
 	assert.Equal(string(it.Prev()), "001")
 }