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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_FAKE_PREFS_H_
18 #define UPDATE_ENGINE_COMMON_FAKE_PREFS_H_
19 
20 #include <map>
21 #include <string>
22 #include <vector>
23 
24 #include <base/macros.h>
25 
26 #include "update_engine/common/prefs_interface.h"
27 
28 namespace chromeos_update_engine {
29 
30 // Implements a fake preference store by storing the value associated with
31 // a key in a std::map, suitable for testing. It doesn't allow to set a value on
32 // a key with a different type than the previously set type. This enforces the
33 // type of a given key to be fixed. Also the class checks that the Get*()
34 // methods aren't called on a key set with a different type.
35 
36 class FakePrefs : public PrefsInterface {
37  public:
38   FakePrefs() = default;
39   ~FakePrefs();
40 
41   // PrefsInterface methods.
42   bool GetString(const std::string& key, std::string* value) const override;
43   bool SetString(const std::string& key, const std::string& value) override;
44   bool GetInt64(const std::string& key, int64_t* value) const override;
45   bool SetInt64(const std::string& key, const int64_t value) override;
46   bool GetBoolean(const std::string& key, bool* value) const override;
47   bool SetBoolean(const std::string& key, const bool value) override;
48 
49   bool Exists(const std::string& key) const override;
50   bool Delete(const std::string& key) override;
51 
52   void AddObserver(const std::string& key,
53                    ObserverInterface* observer) override;
54   void RemoveObserver(const std::string& key,
55                       ObserverInterface* observer) override;
56 
57  private:
58   enum class PrefType {
59     kString,
60     kInt64,
61     kBool,
62   };
63   struct PrefValue {
64     std::string as_str;
65     int64_t as_int64;
66     bool as_bool;
67   };
68 
69   struct PrefTypeValue {
70     PrefType type;
71     PrefValue value;
72   };
73 
74   // Class to store compile-time type-dependent constants.
75   template<typename T>
76   class PrefConsts {
77    public:
78     // The PrefType associated with T.
79     static FakePrefs::PrefType const type;
80 
81     // The data member pointer to PrefValue associated with T.
82     static T FakePrefs::PrefValue::* const member;
83   };
84 
85   // Returns a string representation of the PrefType useful for logging.
86   static std::string GetTypeName(PrefType type);
87 
88   // Checks that the |key| is either not present or has the given |type|.
89   void CheckKeyType(const std::string& key, PrefType type) const;
90 
91   // Helper function to set a value of the passed |key|. It sets the type based
92   // on the template parameter T.
93   template<typename T>
94   void SetValue(const std::string& key, const T& value);
95 
96   // Helper function to get a value from the map checking for invalid calls.
97   // The function fails the test if you attempt to read a value  defined as a
98   // different type. Returns whether the get succeeded.
99   template<typename T>
100   bool GetValue(const std::string& key, T* value) const;
101 
102   // Container for all the key/value pairs.
103   std::map<std::string, PrefTypeValue> values_;
104 
105   // The registered observers watching for changes.
106   std::map<std::string, std::vector<ObserverInterface*>> observers_;
107 
108   DISALLOW_COPY_AND_ASSIGN(FakePrefs);
109 };
110 
111 }  // namespace chromeos_update_engine
112 
113 #endif  // UPDATE_ENGINE_COMMON_FAKE_PREFS_H_
114