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1 //
2 // Copyright (C) 2011 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_INTERFACE_H_
18 #define UPDATE_ENGINE_COMMON_PREFS_INTERFACE_H_
19 
20 #include <stdint.h>
21 
22 #include <string>
23 #include <vector>
24 
25 namespace chromeos_update_engine {
26 
27 // The prefs interface allows access to a persistent preferences
28 // store. The two reasons for providing this as an interface are
29 // testing as well as easier switching to a new implementation in the
30 // future, if necessary.
31 
32 class PrefsInterface {
33  public:
34   // Observer class to be notified about key value changes.
35   class ObserverInterface {
36    public:
37     virtual ~ObserverInterface() = default;
38 
39     // Called when the value is set for the observed |key|.
40     virtual void OnPrefSet(std::string_view key) = 0;
41 
42     // Called when the observed |key| is deleted.
43     virtual void OnPrefDeleted(std::string_view key) = 0;
44   };
45 
46   virtual ~PrefsInterface() = default;
47 
48   // Gets a string |value| associated with |key|. Returns true on
49   // success, false on failure (including when the |key| is not
50   // present in the store).
51   virtual bool GetString(std::string_view key, std::string* value) const = 0;
52 
53   // Associates |key| with a string |value|. Returns true on success,
54   // false otherwise.
55   virtual bool SetString(std::string_view key, std::string_view value) = 0;
56 
57   // Gets an int64_t |value| associated with |key|. Returns true on
58   // success, false on failure (including when the |key| is not
59   // present in the store).
60   virtual bool GetInt64(std::string_view key, int64_t* value) const = 0;
61 
62   // Associates |key| with an int64_t |value|. Returns true on success,
63   // false otherwise.
64   virtual bool SetInt64(std::string_view key, const int64_t value) = 0;
65 
66   // Gets a boolean |value| associated with |key|. Returns true on
67   // success, false on failure (including when the |key| is not
68   // present in the store).
69   virtual bool GetBoolean(std::string_view key, bool* value) const = 0;
70 
71   // Associates |key| with a boolean |value|. Returns true on success,
72   // false otherwise.
73   virtual bool SetBoolean(std::string_view key, const bool value) = 0;
74 
75   // Returns true if the setting exists (i.e. a file with the given key
76   // exists in the prefs directory)
77   virtual bool Exists(std::string_view key) const = 0;
78 
79   // Returns true if successfully deleted the file corresponding to
80   // this key. Calling with non-existent keys does nothing.
81   virtual bool Delete(std::string_view key) = 0;
82 
83   // Deletes the pref key from platform and given namespace subdirectories.
84   // Keys are matched against end of pref keys in each namespace.
85   // Returns true if all deletes were successful.
86   virtual bool Delete(std::string_view pref_key,
87                       const std::vector<std::string>& nss) = 0;
88 
89   // Creates a key which is part of a sub preference.
90   static std::string CreateSubKey(const std::vector<std::string>& ns_with_key);
91 
92   // Returns a list of keys within the namespace.
93   virtual bool GetSubKeys(std::string_view ns,
94                           std::vector<std::string>* keys) const = 0;
95 
96   // Add an observer to watch whenever the given |key| is modified. The
97   // OnPrefSet() and OnPrefDelete() methods will be called whenever any of the
98   // Set*() methods or the Delete() method are called on the given key,
99   // respectively.
100   virtual void AddObserver(std::string_view key,
101                            ObserverInterface* observer) = 0;
102 
103   // Remove an observer added with AddObserver(). The observer won't be called
104   // anymore for future Set*() and Delete() method calls.
105   virtual void RemoveObserver(std::string_view key,
106                               ObserverInterface* observer) = 0;
107 
108  protected:
109   // Key separator used to create sub key and get file names,
110   static const char kKeySeparator = '/';
111 };
112 
113 }  // namespace chromeos_update_engine
114 
115 #endif  // UPDATE_ENGINE_COMMON_PREFS_INTERFACE_H_
116