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      1 /*
      2  * Copyright (C) 2016 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef AAPT_DOMINATOR_TREE_H
     18 #define AAPT_DOMINATOR_TREE_H
     19 
     20 #include <map>
     21 #include <memory>
     22 #include <string>
     23 #include <vector>
     24 
     25 #include "ResourceTable.h"
     26 
     27 namespace aapt {
     28 
     29 /**
     30  * A dominator tree of configurations as defined by resolution rules for Android
     31  * resources.
     32  *
     33  * A node in the tree represents a resource configuration.
     34  *
     35  * The tree has the following property:
     36  *
     37  * Each child of a given configuration defines a strict superset of qualifiers
     38  * and has a value that is at least as specific as that of its ancestors. A
     39  * value is "at least as specific" if it is either identical or it represents a
     40  * stronger requirement.
     41  * For example, v21 is more specific than v11, and w1200dp is more specific than
     42  * w800dp.
     43  *
     44  * The dominator tree relies on the underlying configurations passed to it. If
     45  * the configurations passed to the dominator tree go out of scope, the tree
     46  * will exhibit undefined behavior.
     47  */
     48 class DominatorTree {
     49  public:
     50   explicit DominatorTree(
     51       const std::vector<std::unique_ptr<ResourceConfigValue>>& configs);
     52 
     53   class Node {
     54    public:
     55     explicit Node(ResourceConfigValue* value = nullptr, Node* parent = nullptr)
     56         : value_(value), parent_(parent) {}
     57 
     58     inline ResourceConfigValue* value() const { return value_; }
     59 
     60     inline Node* parent() const { return parent_; }
     61 
     62     inline bool is_root_node() const { return !value_; }
     63 
     64     inline const std::vector<std::unique_ptr<Node>>& children() const {
     65       return children_;
     66     }
     67 
     68     bool TryAddChild(std::unique_ptr<Node> new_child);
     69 
     70    private:
     71     bool AddChild(std::unique_ptr<Node> new_child);
     72     bool Dominates(const Node* other) const;
     73 
     74     ResourceConfigValue* value_;
     75     Node* parent_;
     76     std::vector<std::unique_ptr<Node>> children_;
     77 
     78     DISALLOW_COPY_AND_ASSIGN(Node);
     79   };
     80 
     81   struct Visitor {
     82     virtual ~Visitor() = default;
     83     virtual void VisitTree(const std::string& product, Node* root) = 0;
     84   };
     85 
     86   class BottomUpVisitor : public Visitor {
     87    public:
     88     virtual ~BottomUpVisitor() = default;
     89 
     90     void VisitTree(const std::string& product, Node* root) override {
     91       for (auto& child : root->children()) {
     92         VisitNode(child.get());
     93       }
     94     }
     95 
     96     virtual void VisitConfig(Node* node) = 0;
     97 
     98    private:
     99     void VisitNode(Node* node) {
    100       for (auto& child : node->children()) {
    101         VisitNode(child.get());
    102       }
    103       VisitConfig(node);
    104     }
    105   };
    106 
    107   void Accept(Visitor* visitor);
    108 
    109   inline const std::map<std::string, Node>& product_roots() const {
    110     return product_roots_;
    111   }
    112 
    113  private:
    114   DISALLOW_COPY_AND_ASSIGN(DominatorTree);
    115 
    116   std::map<std::string, Node> product_roots_;
    117 };
    118 
    119 }  // namespace aapt
    120 
    121 #endif  // AAPT_DOMINATOR_TREE_H
    122