tools/aapt2/process/SymbolTable.h

/*
 * Copyright (C) 2015 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_PROCESS_SYMBOLTABLE_H
#define AAPT_PROCESS_SYMBOLTABLE_H

#include <algorithm>
#include <memory>
#include <vector>

#include "android-base/macros.h"
#include "androidfw/AssetManager.h"
#include "utils/JenkinsHash.h"
#include "utils/LruCache.h"

#include "Resource.h"
#include "ResourceTable.h"
#include "ResourceValues.h"
#include "util/Util.h"

namespace aapt {

inline android::hash_t hash_type(const ResourceName& name) {
  std::hash<std::string> str_hash;
  android::hash_t hash = 0;
  hash = android::JenkinsHashMix(hash, (uint32_t)str_hash(name.package));
  hash = android::JenkinsHashMix(hash, (uint32_t)name.type);
  hash = android::JenkinsHashMix(hash, (uint32_t)str_hash(name.entry));
  return hash;
}

inline android::hash_t hash_type(const ResourceId& id) {
  return android::hash_type(id.id);
}

class ISymbolSource;

class SymbolTable {
 public:
  struct Symbol {
    Symbol() : Symbol(Maybe<ResourceId>{}) {}

    explicit Symbol(const Maybe<ResourceId>& i) : Symbol(i, nullptr) {}

    Symbol(const Maybe<ResourceId>& i, const std::shared_ptr<Attribute>& attr)
        : Symbol(i, attr, false) {}

    Symbol(const Maybe<ResourceId>& i, const std::shared_ptr<Attribute>& attr,
           bool pub)
        : id(i), attribute(attr), is_public(pub) {}

    Symbol(const Symbol&) = default;
    Symbol(Symbol&&) = default;
    Symbol& operator=(const Symbol&) = default;
    Symbol& operator=(Symbol&&) = default;

    Maybe<ResourceId> id;
    std::shared_ptr<Attribute> attribute;
    bool is_public = false;
  };

  SymbolTable() : cache_(200), id_cache_(200) {}

  void AppendSource(std::unique_ptr<ISymbolSource> source);
  void PrependSource(std::unique_ptr<ISymbolSource> source);

  /**
   * Never hold on to the result between calls to FindByName or FindById. The
   * results stored in a cache which may evict entries.
   */
  const Symbol* FindByName(const ResourceName& name);
  const Symbol* FindById(const ResourceId& id);

  /**
   * Let's the ISymbolSource decide whether looking up by name or ID is faster,
   * if both are available.
   */
  const Symbol* FindByReference(const Reference& ref);

 private:
  std::vector<std::unique_ptr<ISymbolSource>> sources_;

  // We use shared_ptr because unique_ptr is not supported and
  // we need automatic deletion.
  android::LruCache<ResourceName, std::shared_ptr<Symbol>> cache_;
  android::LruCache<ResourceId, std::shared_ptr<Symbol>> id_cache_;

  DISALLOW_COPY_AND_ASSIGN(SymbolTable);
};

/**
 * An interface that a symbol source implements in order to surface symbol
 * information
 * to the symbol table.
 */
class ISymbolSource {
 public:
  virtual ~ISymbolSource() = default;

  virtual std::unique_ptr<SymbolTable::Symbol> FindByName(
      const ResourceName& name) = 0;
  virtual std::unique_ptr<SymbolTable::Symbol> FindById(ResourceId id) = 0;

  /**
   * Default implementation tries the name if it exists, else the ID.
   */
  virtual std::unique_ptr<SymbolTable::Symbol> FindByReference(
      const Reference& ref) {
    if (ref.name) {
      return FindByName(ref.name.value());
    } else if (ref.id) {
      return FindById(ref.id.value());
    }
    return {};
  }
};

/**
 * Exposes the resources in a ResourceTable as symbols for SymbolTable.
 * Instances of this class must outlive the encompassed ResourceTable.
 * Lookups by ID are ignored.
 */
class ResourceTableSymbolSource : public ISymbolSource {
 public:
  explicit ResourceTableSymbolSource(ResourceTable* table) : table_(table) {}

  std::unique_ptr<SymbolTable::Symbol> FindByName(
      const ResourceName& name) override;

  std::unique_ptr<SymbolTable::Symbol> FindById(ResourceId id) override {
    return {};
  }

 private:
  ResourceTable* table_;

  DISALLOW_COPY_AND_ASSIGN(ResourceTableSymbolSource);
};

class AssetManagerSymbolSource : public ISymbolSource {
 public:
  AssetManagerSymbolSource() = default;

  bool AddAssetPath(const StringPiece& path);

  std::unique_ptr<SymbolTable::Symbol> FindByName(
      const ResourceName& name) override;
  std::unique_ptr<SymbolTable::Symbol> FindById(ResourceId id) override;
  std::unique_ptr<SymbolTable::Symbol> FindByReference(
      const Reference& ref) override;

 private:
  android::AssetManager assets_;

  DISALLOW_COPY_AND_ASSIGN(AssetManagerSymbolSource);
};

}  // namespace aapt

#endif /* AAPT_PROCESS_SYMBOLTABLE_H */