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 
29 namespace 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.
33 class 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 
PrefsBase(StorageInterface * storage)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 
92 class Prefs : public PrefsBase {
93  public:
Prefs()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 
141 class MemoryPrefs : public PrefsBase {
142  public:
MemoryPrefs()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