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1 | // Copyright (c) 2011-present, Facebook, Inc. All rights reserved. |
2 | // This source code is licensed under the BSD-style license found in the | |
3 | // LICENSE file in the root directory of this source tree. An additional grant | |
4 | // of patent rights can be found in the PATENTS file in the same directory. | |
5 | // | |
6 | // Copyright (c) 2011 The LevelDB Authors. All rights reserved. | |
7 | // Use of this source code is governed by a BSD-style license that can be | |
8 | // found in the LICENSE file. See the AUTHORS file for names of contributors. | |
9 | ||
10 | #pragma once | |
11 | ||
12 | #include <set> | |
13 | ||
14 | #include "table/internal_iterator.h" | |
15 | ||
16 | namespace rocksdb { | |
17 | ||
18 | // A internal wrapper class with an interface similar to Iterator that caches | |
19 | // the valid() and key() results for an underlying iterator. | |
20 | // This can help avoid virtual function calls and also gives better | |
21 | // cache locality. | |
22 | class IteratorWrapper { | |
23 | public: | |
24 | IteratorWrapper() : iter_(nullptr), valid_(false) {} | |
25 | explicit IteratorWrapper(InternalIterator* _iter) : iter_(nullptr) { | |
26 | Set(_iter); | |
27 | } | |
28 | ~IteratorWrapper() {} | |
29 | InternalIterator* iter() const { return iter_; } | |
30 | ||
31 | // Set the underlying Iterator to _iter and return | |
32 | // previous underlying Iterator. | |
33 | InternalIterator* Set(InternalIterator* _iter) { | |
34 | InternalIterator* old_iter = iter_; | |
35 | ||
36 | iter_ = _iter; | |
37 | if (iter_ == nullptr) { | |
38 | valid_ = false; | |
39 | } else { | |
40 | Update(); | |
41 | } | |
42 | return old_iter; | |
43 | } | |
44 | ||
45 | void DeleteIter(bool is_arena_mode) { | |
46 | if (iter_) { | |
47 | if (!is_arena_mode) { | |
48 | delete iter_; | |
49 | } else { | |
50 | iter_->~InternalIterator(); | |
51 | } | |
52 | } | |
53 | } | |
54 | ||
55 | // Iterator interface methods | |
56 | bool Valid() const { return valid_; } | |
57 | Slice key() const { assert(Valid()); return key_; } | |
58 | Slice value() const { assert(Valid()); return iter_->value(); } | |
59 | // Methods below require iter() != nullptr | |
60 | Status status() const { assert(iter_); return iter_->status(); } | |
61 | void Next() { assert(iter_); iter_->Next(); Update(); } | |
62 | void Prev() { assert(iter_); iter_->Prev(); Update(); } | |
63 | void Seek(const Slice& k) { assert(iter_); iter_->Seek(k); Update(); } | |
64 | void SeekForPrev(const Slice& k) { | |
65 | assert(iter_); | |
66 | iter_->SeekForPrev(k); | |
67 | Update(); | |
68 | } | |
69 | void SeekToFirst() { assert(iter_); iter_->SeekToFirst(); Update(); } | |
70 | void SeekToLast() { assert(iter_); iter_->SeekToLast(); Update(); } | |
71 | ||
72 | void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) { | |
73 | assert(iter_); | |
74 | iter_->SetPinnedItersMgr(pinned_iters_mgr); | |
75 | } | |
76 | bool IsKeyPinned() const { | |
77 | assert(Valid()); | |
78 | return iter_->IsKeyPinned(); | |
79 | } | |
80 | bool IsValuePinned() const { | |
81 | assert(Valid()); | |
82 | return iter_->IsValuePinned(); | |
83 | } | |
84 | ||
85 | private: | |
86 | void Update() { | |
87 | valid_ = iter_->Valid(); | |
88 | if (valid_) { | |
89 | key_ = iter_->key(); | |
90 | } | |
91 | } | |
92 | ||
93 | InternalIterator* iter_; | |
94 | bool valid_; | |
95 | Slice key_; | |
96 | }; | |
97 | ||
98 | class Arena; | |
99 | // Return an empty iterator (yields nothing) allocated from arena. | |
100 | extern InternalIterator* NewEmptyInternalIterator(Arena* arena); | |
101 | ||
102 | // Return an empty iterator with the specified status, allocated arena. | |
103 | extern InternalIterator* NewErrorInternalIterator(const Status& status, | |
104 | Arena* arena); | |
105 | ||
106 | } // namespace rocksdb |