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
3 // found in the LICENSE file.
5 #ifndef UI_BASE_MODELS_TREE_NODE_ITERATOR_H_
6 #define UI_BASE_MODELS_TREE_NODE_ITERATOR_H_
10 #include "base/basictypes.h"
11 #include "base/logging.h"
15 // Iterator that iterates over the descendants of a node. The iteration does
16 // not include the node itself, only the descendants. The following illustrates
18 // while (iterator.has_next()) {
19 // Node* node = iterator.Next();
20 // // do something with node.
22 template <class NodeType>
23 class TreeNodeIterator {
25 // This contructor accepts an optional filter function |prune| which could be
26 // used to prune complete branches of the tree. The filter function will be
27 // evaluated on each tree node and if it evaluates to true the node and all
28 // its descendants will be skipped by the iterator.
29 TreeNodeIterator(NodeType* node, bool (*prune)(NodeType*))
33 // Move forward through the children list until the first non prunable node.
34 // This is to satisfy the iterator invariant that the current index in the
35 // Position at the top of the _positions list must point to a node the
36 // iterator will be returning.
37 for (; index < node->child_count(); ++index)
38 if (!prune || !prune(node->GetChild(index)))
41 if (index < node->child_count())
42 positions_.push(Position<NodeType>(node, index));
45 explicit TreeNodeIterator(NodeType* node) : prune_(NULL) {
47 positions_.push(Position<NodeType>(node, 0));
50 // Returns true if there are more descendants.
51 bool has_next() const { return !positions_.empty(); }
53 // Returns the next descendant.
60 // There must always be a valid node in the current Position index.
61 NodeType* result = positions_.top().node->GetChild(positions_.top().index);
63 // Make sure we don't attempt to visit result again.
64 positions_.top().index++;
66 // Iterate over result's children.
67 positions_.push(Position<NodeType>(result, 0));
69 // Advance to next valid node by skipping over the pruned nodes and the
70 // empty Positions. At the end of this loop two cases are possible:
71 // - the current index of the top() Position points to a valid node
72 // - the _position list is empty, the iterator has_next() will return false.
73 while (!positions_.empty()) {
74 if (positions_.top().index >= positions_.top().node->child_count())
75 positions_.pop(); // This Position is all processed, move to the next.
77 prune_(positions_.top().node->GetChild(positions_.top().index)))
78 positions_.top().index++; // Prune the branch.
80 break; // Now positioned at the next node to be returned.
87 template <class PositionNodeType>
89 Position(PositionNodeType* node, int index) : node(node), index(index) {}
90 Position() : node(NULL), index(-1) {}
92 PositionNodeType* node;
96 std::stack<Position<NodeType> > positions_;
97 bool (*prune_)(NodeType*);
99 DISALLOW_COPY_AND_ASSIGN(TreeNodeIterator);
104 #endif // UI_BASE_MODELS_TREE_NODE_ITERATOR_H_