tools/aapt2/DominatorTree.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef AAPT_DOMINATOR_TREE_H
#define AAPT_DOMINATOR_TREE_H

#include "ResourceTable.h"

#include <map>
#include <memory>
#include <string>
#include <vector>

namespace aapt {

/**
 * A dominator tree of configurations as defined by resolution rules for Android
 * resources.
 *
 * A node in the tree represents a resource configuration.
 *
 * The tree has the following property:
 *
 * Each child of a given configuration defines a strict superset of qualifiers
 * and has a value that is at least as specific as that of its ancestors. A
 * value is "at least as specific" if it is either identical or it represents a
 * stronger requirement.
 * For example, v21 is more specific than v11, and w1200dp is more specific than
 * w800dp.
 *
 * The dominator tree relies on the underlying configurations passed to it. If
 * the configurations passed to the dominator tree go out of scope, the tree
 * will exhibit undefined behavior.
 */
class DominatorTree {
public:
    explicit DominatorTree(const std::vector<std::unique_ptr<ResourceConfigValue>>& configs);

    class Node {
    public:
        explicit Node(ResourceConfigValue* value = nullptr, Node* parent = nullptr) :
                mValue(value), mParent(parent) {
        }

        inline ResourceConfigValue* value() const {
            return mValue;
        }

        inline Node* parent() const {
            return mParent;
        }

        inline bool isRootNode() const {
            return !mValue;
        }

        inline const std::vector<std::unique_ptr<Node>>& children() const {
            return mChildren;
        }

        bool tryAddChild(std::unique_ptr<Node> newChild);

    private:
        bool addChild(std::unique_ptr<Node> newChild);
        bool dominates(const Node* other) const;

        ResourceConfigValue* mValue;
        Node* mParent;
        std::vector<std::unique_ptr<Node>> mChildren;

        DISALLOW_COPY_AND_ASSIGN(Node);
    };

    struct Visitor {
        virtual ~Visitor() = default;
        virtual void visitTree(const std::string& product, Node* root) = 0;
    };

    class BottomUpVisitor : public Visitor {
    public:
        virtual ~BottomUpVisitor() = default;

        void visitTree(const std::string& product, Node* root) override {
            for (auto& child : root->children()) {
                visitNode(child.get());
            }
        }

        virtual void visitConfig(Node* node) = 0;

    private:
        void visitNode(Node* node) {
            for (auto& child : node->children()) {
                visitNode(child.get());
            }
            visitConfig(node);
        }
    };

    void accept(Visitor* visitor);

    inline const std::map<std::string, Node>& getProductRoots() const {
        return mProductRoots;
    }

private:
    DISALLOW_COPY_AND_ASSIGN(DominatorTree);

    std::map<std::string, Node> mProductRoots;
};

} // namespace aapt

#endif // AAPT_DOMINATOR_TREE_H