1 //
2 // Copyright (C) 2014 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_UPDATE_MANAGER_POLICY_UTILS_H_
18 #define UPDATE_ENGINE_UPDATE_MANAGER_POLICY_UTILS_H_
19 
20 #include <string>
21 #include <vector>
22 
23 #include "update_engine/update_manager/policy.h"
24 
25 // Checks that the passed pointer value is not null, returning kFailed on the
26 // current context and setting the *error description when it is null. The
27 // intended use is to validate variable failures while using
28 // EvaluationContext::GetValue, for example:
29 //
30 //   const int* my_value = ec->GetValue(state->my_provider()->var_my_value());
31 //   POLICY_CHECK_VALUE_AND_FAIL(my_value, error);
32 //
33 #define POLICY_CHECK_VALUE_AND_FAIL(ptr, error)    \
34   do {                                             \
35     if ((ptr) == nullptr) {                        \
36       *(error) = #ptr " is required but is null."; \
37       return EvalStatus::kFailed;                  \
38     }                                              \
39   } while (false)
40 
41 namespace chromeos_update_manager {
42 
43 // Call the passed-in Policy method on a series of Policy implementations, until
44 // one of them renders a decision by returning a value other than
45 // |EvalStatus::kContinue|.
46 template <typename T, typename R, typename... Args>
47 EvalStatus ConsultPolicies(const std::vector<Policy const*> policies,
48                            T policy_method,
49                            EvaluationContext* ec,
50                            State* state,
51                            std::string* error,
52                            R* result,
53                            Args... args) {
54   for (auto policy : policies) {
55     EvalStatus status =
56         (policy->*policy_method)(ec, state, error, result, args...);
57     if (status != EvalStatus::kContinue) {
58       LOG(INFO) << "decision by " << policy->PolicyRequestName(policy_method);
59       return status;
60     }
61   }
62   return EvalStatus::kContinue;
63 }
64 
65 // Base class implementation that returns |EvalStatus::kContinue| for all
66 // decisions, to be used as a base-class for various Policy facets that only
67 // pertain to certain situations. This might be better folded into Policy
68 // instead of using pure-virtual methods on that class.
69 class PolicyImplBase : public Policy {
70  public:
71   // Policy overrides.
72   EvalStatus UpdateCheckAllowed(EvaluationContext* ec,
73                                 State* state,
74                                 std::string* error,
75                                 UpdateCheckParams* result) const override {
76     return EvalStatus::kContinue;
77   };
78 
79   EvalStatus UpdateCanBeApplied(
80       EvaluationContext* ec,
81       State* state,
82       std::string* error,
83       chromeos_update_engine::ErrorCode* result,
84       chromeos_update_engine::InstallPlan* install_plan) const override {
85     return EvalStatus::kContinue;
86   };
87 
88   EvalStatus UpdateCanStart(EvaluationContext* ec,
89                             State* state,
90                             std::string* error,
91                             UpdateDownloadParams* result,
92                             UpdateState update_state) const override {
93     return EvalStatus::kContinue;
94   };
95 
96   EvalStatus UpdateDownloadAllowed(EvaluationContext* ec,
97                                    State* state,
98                                    std::string* error,
99                                    bool* result) const override {
100     return EvalStatus::kContinue;
101   };
102 
103   EvalStatus P2PEnabled(EvaluationContext* ec,
104                         State* state,
105                         std::string* error,
106                         bool* result) const override {
107     return EvalStatus::kContinue;
108   };
109 
110   EvalStatus P2PEnabledChanged(EvaluationContext* ec,
111                                State* state,
112                                std::string* error,
113                                bool* result,
114                                bool prev_result) const override {
115     return EvalStatus::kContinue;
116   };
117 };
118 
119 }  // namespace chromeos_update_manager
120 
121 #endif  // UPDATE_ENGINE_UPDATE_MANAGER_POLICY_UTILS_H_
122