summaryrefslogtreecommitdiffstats
path: root/Source/cmLinkedTree.h
blob: 975f05240cca426b60abc3cadef291539c168223 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
   file Copyright.txt or https://cmake.org/licensing for details.  */
#ifndef cmLinkedTree_h
#define cmLinkedTree_h

#include "cmConfigure.h" // IWYU pragma: keep

#include <assert.h>
#include <iterator>
#include <vector>

/**
  @brief A adaptor for traversing a tree structure in a vector

  This class is not intended to be wholly generic like a standard library
  container adaptor.  Mostly it exists to facilitate code sharing for the
  needs of the cmState.  For example, the Truncate() method is a specific
  requirement of the cmState.

  An empty cmLinkedTree provides a Root() method, and an Push() method,
  each of which return iterators.  A Tree can be built up by extending
  from the root, and then extending from any other iterator.

  An iterator resulting from this tree construction can be
  forward-only-iterated toward the root.  Extending the tree never
  invalidates existing iterators.
 */
template <typename T>
class cmLinkedTree
{
  typedef typename std::vector<T>::size_type PositionType;
  typedef T* PointerType;
  typedef T& ReferenceType;

public:
  class iterator : public std::iterator<std::forward_iterator_tag, T>
  {
    friend class cmLinkedTree;
    cmLinkedTree* Tree;

    // The Position is always 'one past the end'.
    PositionType Position;

    iterator(cmLinkedTree* tree, PositionType pos)
      : Tree(tree)
      , Position(pos)
    {
    }

  public:
    iterator()
      : Tree(nullptr)
      , Position(0)
    {
    }

    void operator++()
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      assert(this->Position <= this->Tree->Data.size());
      assert(this->Position > 0);
      this->Position = this->Tree->UpPositions[this->Position - 1];
    }

    PointerType operator->() const
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      assert(this->Position <= this->Tree->Data.size());
      assert(this->Position > 0);
      return this->Tree->GetPointer(this->Position - 1);
    }

    PointerType operator->()
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      assert(this->Position <= this->Tree->Data.size());
      assert(this->Position > 0);
      return this->Tree->GetPointer(this->Position - 1);
    }

    ReferenceType operator*() const
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      assert(this->Position <= this->Tree->Data.size());
      assert(this->Position > 0);
      return this->Tree->GetReference(this->Position - 1);
    }

    ReferenceType operator*()
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      assert(this->Position <= this->Tree->Data.size());
      assert(this->Position > 0);
      return this->Tree->GetReference(this->Position - 1);
    }

    bool operator==(iterator other) const
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      assert(this->Tree == other.Tree);
      return this->Position == other.Position;
    }

    bool operator!=(iterator other) const
    {
      assert(this->Tree);
      assert(this->Tree->UpPositions.size() == this->Tree->Data.size());
      return !(*this == other);
    }

    bool IsValid() const
    {
      if (!this->Tree) {
        return false;
      }
      return this->Position <= this->Tree->Data.size();
    }

    bool StrictWeakOrdered(iterator other) const
    {
      assert(this->Tree);
      assert(this->Tree == other.Tree);
      return this->Position < other.Position;
    }
  };

  iterator Root() const
  {
    return iterator(const_cast<cmLinkedTree*>(this), 0);
  }

  iterator Push(iterator it) { return Push_impl(it, T()); }

  iterator Push(iterator it, T t) { return Push_impl(it, std::move(t)); }

  bool IsLast(iterator it) { return it.Position == this->Data.size(); }

  iterator Pop(iterator it)
  {
    assert(!this->Data.empty());
    assert(this->UpPositions.size() == this->Data.size());
    bool const isLast = this->IsLast(it);
    ++it;
    // If this is the last entry then no other entry can refer
    // to it so we can drop its storage.
    if (isLast) {
      this->Data.pop_back();
      this->UpPositions.pop_back();
    }
    return it;
  }

  iterator Truncate()
  {
    assert(!this->UpPositions.empty());
    this->UpPositions.erase(this->UpPositions.begin() + 1,
                            this->UpPositions.end());
    assert(!this->Data.empty());
    this->Data.erase(this->Data.begin() + 1, this->Data.end());
    return iterator(this, 1);
  }

  void Clear()
  {
    this->UpPositions.clear();
    this->Data.clear();
  }

private:
  T& GetReference(PositionType pos) { return this->Data[pos]; }

  T* GetPointer(PositionType pos) { return &this->Data[pos]; }

  iterator Push_impl(iterator it, T&& t)
  {
    assert(this->UpPositions.size() == this->Data.size());
    assert(it.Position <= this->UpPositions.size());
    this->UpPositions.push_back(it.Position);
    this->Data.push_back(std::move(t));
    return iterator(this, this->UpPositions.size());
  }

  std::vector<T> Data;
  std::vector<PositionType> UpPositions;
};

#endif