1//
2// Copyright (C) 2012 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 UPDATE_ENGINE_COMMON_PREFS_H_
18#define UPDATE_ENGINE_COMMON_PREFS_H_
19
20#include <map>
21#include <string>
22#include <vector>
23
24#include <base/files/file_path.h>
25
26#include "gtest/gtest_prod.h"  // for FRIEND_TEST
27#include "update_engine/common/prefs_interface.h"
28
29namespace chromeos_update_engine {
30
31// Implements a preference store by storing the value associated with a key
32// in a given storage passed during construction.
33class PrefsBase : public PrefsInterface {
34 public:
35  // Storage interface used to set and retrieve keys.
36  class StorageInterface {
37   public:
38    StorageInterface() = default;
39    virtual ~StorageInterface() = default;
40
41    // Get the key named |key| and store its value in the referenced |value|.
42    // Returns whether the operation succeeded.
43    virtual bool GetKey(const std::string& key, std::string* value) const = 0;
44
45    // Set the value of the key named |key| to |value| regardless of the
46    // previous value. Returns whether the operation succeeded.
47    virtual bool SetKey(const std::string& key, const std::string& value) = 0;
48
49    // Returns whether the key named |key| exists.
50    virtual bool KeyExists(const std::string& key) const = 0;
51
52    // Deletes the value associated with the key name |key|. Returns whether the
53    // key was deleted.
54    virtual bool DeleteKey(const std::string& key) = 0;
55
56   private:
57    DISALLOW_COPY_AND_ASSIGN(StorageInterface);
58  };
59
60  explicit PrefsBase(StorageInterface* storage) : storage_(storage) {}
61
62  // PrefsInterface methods.
63  bool GetString(const std::string& key, std::string* value) const override;
64  bool SetString(const std::string& key, const std::string& value) override;
65  bool GetInt64(const std::string& key, int64_t* value) const override;
66  bool SetInt64(const std::string& key, const int64_t value) override;
67  bool GetBoolean(const std::string& key, bool* value) const override;
68  bool SetBoolean(const std::string& key, const bool value) override;
69
70  bool Exists(const std::string& key) const override;
71  bool Delete(const std::string& key) override;
72
73  void AddObserver(const std::string& key,
74                   ObserverInterface* observer) override;
75  void RemoveObserver(const std::string& key,
76                      ObserverInterface* observer) override;
77
78 private:
79  // The registered observers watching for changes.
80  std::map<std::string, std::vector<ObserverInterface*>> observers_;
81
82  // The concrete implementation of the storage used for the keys.
83  StorageInterface* storage_;
84
85  DISALLOW_COPY_AND_ASSIGN(PrefsBase);
86};
87
88// Implements a preference store by storing the value associated with
89// a key in a separate file named after the key under a preference
90// store directory.
91
92class Prefs : public PrefsBase {
93 public:
94  Prefs() : PrefsBase(&file_storage_) {}
95
96  // Initializes the store by associating this object with |prefs_dir|
97  // as the preference store directory. Returns true on success, false
98  // otherwise.
99  bool Init(const base::FilePath& prefs_dir);
100
101 private:
102  FRIEND_TEST(PrefsTest, GetFileNameForKey);
103  FRIEND_TEST(PrefsTest, GetFileNameForKeyBadCharacter);
104  FRIEND_TEST(PrefsTest, GetFileNameForKeyEmpty);
105
106  class FileStorage : public PrefsBase::StorageInterface {
107   public:
108    FileStorage() = default;
109
110    bool Init(const base::FilePath& prefs_dir);
111
112    // PrefsBase::StorageInterface overrides.
113    bool GetKey(const std::string& key, std::string* value) const override;
114    bool SetKey(const std::string& key, const std::string& value) override;
115    bool KeyExists(const std::string& key) const override;
116    bool DeleteKey(const std::string& key) override;
117
118   private:
119    FRIEND_TEST(PrefsTest, GetFileNameForKey);
120    FRIEND_TEST(PrefsTest, GetFileNameForKeyBadCharacter);
121    FRIEND_TEST(PrefsTest, GetFileNameForKeyEmpty);
122
123    // Sets |filename| to the full path to the file containing the data
124    // associated with |key|. Returns true on success, false otherwise.
125    bool GetFileNameForKey(const std::string& key,
126                           base::FilePath* filename) const;
127
128    // Preference store directory.
129    base::FilePath prefs_dir_;
130  };
131
132  // The concrete file storage implementation.
133  FileStorage file_storage_;
134
135  DISALLOW_COPY_AND_ASSIGN(Prefs);
136};
137
138// Implements a preference store in memory. The stored values are lost when the
139// object is destroyed.
140
141class MemoryPrefs : public PrefsBase {
142 public:
143  MemoryPrefs() : PrefsBase(&mem_storage_) {}
144
145 private:
146  class MemoryStorage : public PrefsBase::StorageInterface {
147   public:
148    MemoryStorage() = default;
149
150    // PrefsBase::StorageInterface overrides.
151    bool GetKey(const std::string& key, std::string* value) const override;
152    bool SetKey(const std::string& key, const std::string& value) override;
153    bool KeyExists(const std::string& key) const override;
154    bool DeleteKey(const std::string& key) override;
155
156   private:
157    // The std::map holding the values in memory.
158    std::map<std::string, std::string> values_;
159  };
160
161  // The concrete memory storage implementation.
162  MemoryStorage mem_storage_;
163
164  DISALLOW_COPY_AND_ASSIGN(MemoryPrefs);
165};
166}  // namespace chromeos_update_engine
167
168#endif  // UPDATE_ENGINE_COMMON_PREFS_H_
169