1  // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
 2  // Use of this source code is governed by a BSD-style license that can be
 3  // found in the LICENSE file. See the AUTHORS file for names of contributors.
 4  
 5  #include "leveldb/iterator.h"
 6  
 7  namespace leveldb {
 8  
 9  Iterator::Iterator() {
10    cleanup_head_.function = nullptr;
11    cleanup_head_.next = nullptr;
12  }
13  
14  Iterator::~Iterator() {
15    if (!cleanup_head_.IsEmpty()) {
16      cleanup_head_.Run();
17      for (CleanupNode* node = cleanup_head_.next; node != nullptr;) {
18        node->Run();
19        CleanupNode* next_node = node->next;
20        delete node;
21        node = next_node;
22      }
23    }
24  }
25  
26  void Iterator::RegisterCleanup(CleanupFunction func, void* arg1, void* arg2) {
27    assert(func != nullptr);
28    CleanupNode* node;
29    if (cleanup_head_.IsEmpty()) {
30      node = &cleanup_head_;
31    } else {
32      node = new CleanupNode();
33      node->next = cleanup_head_.next;
34      cleanup_head_.next = node;
35    }
36    node->function = func;
37    node->arg1 = arg1;
38    node->arg2 = arg2;
39  }
40  
41  namespace {
42  
43  class EmptyIterator : public Iterator {
44   public:
45    EmptyIterator(const Status& s) : status_(s) {}
46    ~EmptyIterator() override = default;
47  
48    bool Valid() const override { return false; }
49    void Seek(const Slice& target) override {}
50    void SeekToFirst() override {}
51    void SeekToLast() override {}
52    void Next() override { assert(false); }
53    void Prev() override { assert(false); }
54    Slice key() const override {
55      assert(false);
56      return Slice();
57    }
58    Slice value() const override {
59      assert(false);
60      return Slice();
61    }
62    Status status() const override { return status_; }
63  
64   private:
65    Status status_;
66  };
67  
68  }  // anonymous namespace
69  
70  Iterator* NewEmptyIterator() { return new EmptyIterator(Status::OK()); }
71  
72  Iterator* NewErrorIterator(const Status& status) {
73    return new EmptyIterator(status);
74  }
75  
76  }  // namespace leveldb