1 /*
2  * Copyright (c) 2021 Huawei Device Co., Ltd.
3  * Licensed under the Apache License, Version 2.0 (the "License");
4  * you may not use this file except in compliance with the License.
5  * You may obtain a copy of the License at
6  *
7  *     http://www.apache.org/licenses/LICENSE-2.0
8  *
9  * Unless required by applicable law or agreed to in writing, software
10  * distributed under the License is distributed on an "AS IS" BASIS,
11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  * See the License for the specific language governing permissions and
13  * limitations under the License.
14  */
15 
16 #ifndef RESULT_ENTRIES_WINDOW_H
17 #define RESULT_ENTRIES_WINDOW_H
18 
19 #include "macro_utils.h"
20 #include "ikvdb_raw_cursor.h"
21 
22 namespace DistributedDB {
23 class ResultEntriesWindow {
24 public:
25     ResultEntriesWindow();
26     ~ResultEntriesWindow();
27     int Init(IKvDBRawCursor *rawCursor, int64_t windowSize, double scale);
28     DISABLE_COPY_ASSIGN_MOVE(ResultEntriesWindow);
29     int GetTotalCount() const;
30     int GetCurrentPosition() const;
31     bool MoveToPosition(int position);
32     int GetEntry(Entry &entry) const;
33 
34 private:
35     void ResetWindow();
36     int SetCursor(int begin, int target);
37     int LoadData(int begin, int target) const;
38 
39 private:
40     static const int64_t MAX_WINDOW_SIZE = 0xFFFFFFFFL; // 4G - 1
41     mutable IKvDBRawCursor *rawCursor_;
42     int64_t windowSize_;
43     int totalCount_;
44     mutable std::vector<Entry> buffer_;
45     int begin_;
46     int currentPosition_;
47 };
48 } // namespace DistributedDB
49 
50 #endif // RESULT_ENTRIES_WINDOW_H
51