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1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #ifndef UI_BASE_MODELS_TREE_NODE_ITERATOR_H_ | 5 #ifndef UI_BASE_MODELS_TREE_NODE_ITERATOR_H_ |
6 #define UI_BASE_MODELS_TREE_NODE_ITERATOR_H_ | 6 #define UI_BASE_MODELS_TREE_NODE_ITERATOR_H_ |
7 #pragma once | 7 #pragma once |
8 | 8 |
9 #include <stack> | 9 #include <stack> |
10 | 10 |
11 #include "base/basictypes.h" | 11 #include "base/basictypes.h" |
12 #include "base/logging.h" | 12 #include "base/logging.h" |
13 | 13 |
14 namespace ui { | 14 namespace ui { |
15 | 15 |
16 // Iterator that iterates over the descendants of a node. The iteration does | 16 // Iterator that iterates over the descendants of a node. The iteration does |
17 // not include the node itself, only the descendants. The following illustrates | 17 // not include the node itself, only the descendants. The following illustrates |
18 // typical usage: | 18 // typical usage: |
19 // while (iterator.has_next()) { | 19 // while (iterator.has_next()) { |
20 // Node* node = iterator.Next(); | 20 // Node* node = iterator.Next(); |
21 // // do something with node. | 21 // // do something with node. |
22 // } | 22 // } |
23 template <class NodeType> | 23 template <class NodeType> |
24 class TreeNodeIterator { | 24 class TreeNodeIterator { |
25 public: | 25 public: |
26 // This contructor accepts an optional filter function |prune| which could be | 26 explicit TreeNodeIterator(NodeType* node) { |
27 // used to prune complete branches of the tree. The filter function will be | |
28 // evaluated on each tree node and if it evaluates to true the node and all | |
29 // its descendants will be skipped by the iterator. | |
30 TreeNodeIterator(NodeType* node, bool (*prune)(NodeType*)) | |
31 : prune_(prune) { | |
32 int index = 0; | |
33 | |
34 // Move forward through the children list until the first non prunable node. | |
35 // This is to satisfy the iterator invariant that the current index in the | |
36 // Position at the top of the _positions list must point to a node the | |
37 // iterator will be returning. | |
38 for (; index < node->child_count(); ++index) | |
39 if (!prune || !prune(node->GetChild(index))) | |
40 break; | |
41 | |
42 if (index < node->child_count()) | |
43 positions_.push(Position<NodeType>(node, index)); | |
44 } | |
45 | |
46 explicit TreeNodeIterator(NodeType* node) : prune_(NULL) { | |
47 if (!node->empty()) | 27 if (!node->empty()) |
48 positions_.push(Position<NodeType>(node, 0)); | 28 positions_.push(Position<NodeType>(node, 0)); |
49 } | 29 } |
50 | 30 |
51 // Returns true if there are more descendants. | 31 // Returns true if there are more descendants. |
52 bool has_next() const { return !positions_.empty(); } | 32 bool has_next() const { return !positions_.empty(); } |
53 | 33 |
54 // Returns the next descendant. | 34 // Returns the next descendant. |
55 NodeType* Next() { | 35 NodeType* Next() { |
56 if (!has_next()) { | 36 if (!has_next()) { |
57 NOTREACHED(); | 37 NOTREACHED(); |
58 return NULL; | 38 return NULL; |
59 } | 39 } |
60 | 40 |
61 // There must always be a valid node in the current Position index. | 41 // There must always be a valid node in the current Position index. |
62 NodeType* result = positions_.top().node->GetChild(positions_.top().index); | 42 NodeType* result = positions_.top().node->GetChild(positions_.top().index); |
63 | 43 |
64 // Make sure we don't attempt to visit result again. | 44 // Make sure we don't attempt to visit result again. |
65 positions_.top().index++; | 45 positions_.top().index++; |
66 | 46 |
67 // Iterate over result's children. | 47 // Iterate over result's children. |
68 positions_.push(Position<NodeType>(result, 0)); | 48 positions_.push(Position<NodeType>(result, 0)); |
69 | 49 |
70 // Advance to next valid node by skipping over the pruned nodes and the | 50 while (!positions_.empty() && |
71 // empty Positions. At the end of this loop two cases are possible: | 51 positions_.top().index >= positions_.top().node->child_count()) { |
72 // - the current index of the top() Position points to a valid node | 52 positions_.pop(); // This Position is all processed, move to the next. |
73 // - the _position list is empty, the iterator has_next() will return false. | |
74 while (!positions_.empty()) { | |
75 if (positions_.top().index >= positions_.top().node->child_count()) | |
76 positions_.pop(); // This Position is all processed, move to the next. | |
77 else if (prune_ && | |
78 prune_(positions_.top().node->GetChild(positions_.top().index))) | |
79 positions_.top().index++; // Prune the branch. | |
80 else | |
81 break; // Now positioned at the next node to be returned. | |
82 } | 53 } |
83 | 54 |
84 return result; | 55 return result; |
85 } | 56 } |
86 | 57 |
87 private: | 58 private: |
88 template <class PositionNodeType> | 59 template <class PositionNodeType> |
89 struct Position { | 60 struct Position { |
90 Position(PositionNodeType* node, int index) : node(node), index(index) {} | 61 Position(PositionNodeType* node, int index) : node(node), index(index) {} |
91 Position() : node(NULL), index(-1) {} | 62 Position() : node(NULL), index(-1) {} |
92 | 63 |
93 PositionNodeType* node; | 64 PositionNodeType* node; |
94 int index; | 65 int index; |
95 }; | 66 }; |
96 | 67 |
97 std::stack<Position<NodeType> > positions_; | 68 std::stack<Position<NodeType> > positions_; |
98 bool (*prune_)(NodeType*); | |
99 | 69 |
100 DISALLOW_COPY_AND_ASSIGN(TreeNodeIterator); | 70 DISALLOW_COPY_AND_ASSIGN(TreeNodeIterator); |
101 }; | 71 }; |
102 | 72 |
103 } // namespace ui | 73 } // namespace ui |
104 | 74 |
105 #endif // UI_BASE_MODELS_TREE_NODE_ITERATOR_H_ | 75 #endif // UI_BASE_MODELS_TREE_NODE_ITERATOR_H_ |
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