implement btree.item on item itelf, not only its pointer. (#254)

Per #186, this may help reduce allocation overhead.

Co-authored-by: romelukaku <[email protected]>

memdb.go

@@ -26,20 +26,20 @@ type item struct {
 }
 
 // Less implements btree.Item.
-func (i *item) Less(other btree.Item) bool {
+func (i item) Less(other btree.Item) bool {
 	// this considers nil == []byte{}, but that's ok since we handle nil endpoints
 	// in iterators specially anyway
-	return bytes.Compare(i.key, other.(*item).key) == -1
+	return bytes.Compare(i.key, other.(item).key) == -1
 }
 
 // newKey creates a new key item.
-func newKey(key []byte) *item {
-	return &item{key: key}
+func newKey(key []byte) item {
+	return item{key: key}
 }
 
 // newPair creates a new pair item.
-func newPair(key, value []byte) *item {
-	return &item{key: key, value: value}
+func newPair(key, value []byte) item {
+	return item{key: key, value: value}
 }
 
 // MemDB is an in-memory database backend using a B-tree for storage.
@@ -73,7 +73,7 @@ func (db *MemDB) Get(key []byte) ([]byte, error) {
 
 	i := db.btree.Get(newKey(key))
 	if i != nil {
-		return i.(*item).value, nil
+		return i.(item).value, nil
 	}
 	return nil, nil
 }
@@ -150,7 +150,7 @@ func (db *MemDB) Print() error {
 	defer db.mtx.RUnlock()
 
 	db.btree.Ascend(func(i btree.Item) bool {
-		item := i.(*item)
+		item := i.(item)
 		fmt.Printf("[%X]:\t[%X]\n", item.key, item.value)
 		return true
 	})

memdb_iterator.go

@@ -56,7 +56,7 @@ func newMemDBIteratorMtxChoice(db *MemDB, start []byte, end []byte, reverse bool
 			abortLessThan []byte
 		)
 		visitor := func(i btree.Item) bool {
-			item := i.(*item)
+			item := i.(item)
 			if skipEqual != nil && bytes.Equal(item.key, skipEqual) {
 				skipEqual = nil
 				return true
@@ -67,7 +67,7 @@ func newMemDBIteratorMtxChoice(db *MemDB, start []byte, end []byte, reverse bool
 			select {
 			case <-ctx.Done():
 				return false
-			case ch <- item:
+			case ch <- &item:
 				return true
 			}
 		}