1 /* 2 * Copyright (C) 2022 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 ART_LIBARTTOOLS_TOOLS_SYSTEM_PROPERTIES_H_ 18 #define ART_LIBARTTOOLS_TOOLS_SYSTEM_PROPERTIES_H_ 19 20 #include <string> 21 22 #include "android-base/parsebool.h" 23 #include "android-base/properties.h" 24 25 namespace art { 26 namespace tools { 27 28 // A class for getting system properties with fallback lookup support. Different from 29 // android::base::GetProperty, this class is mockable. 30 class SystemProperties { 31 public: 32 virtual ~SystemProperties() = default; 33 34 // Returns the current value of the system property `key`, or `default_value` if the property 35 // doesn't have a value. Get(const std::string & key,const std::string & default_value)36 std::string Get(const std::string& key, const std::string& default_value) const { 37 std::string value = GetProperty(key); 38 if (!value.empty()) { 39 return value; 40 } 41 return default_value; 42 } 43 44 // Same as above, but allows specifying one or more fallback keys. The last argument is a string 45 // default value that will be used if none of the given keys has a value. 46 // 47 // Usage: 48 // 49 // Look up for "key_1", then "key_2", then "key_3". If none of them has a value, return "default": 50 // Get("key_1", "key_2", "key_3", /*default_value=*/"default") 51 template <typename... Args> Get(const std::string & key,const std::string & fallback_key,Args...args)52 std::string Get(const std::string& key, const std::string& fallback_key, Args... args) const { 53 return Get(key, Get(fallback_key, args...)); 54 } 55 56 // Returns the current value of the system property `key` with zero or more fallback keys, or an 57 // empty string if none of the given keys has a value. 58 // 59 // Usage: 60 // 61 // Look up for "key_1". If it doesn't have a value, return an empty string: 62 // GetOrEmpty("key_1") 63 // 64 // Look up for "key_1", then "key_2", then "key_3". If none of them has a value, return an empty 65 // string: 66 // GetOrEmpty("key_1", "key_2", "key_3") 67 template <typename... Args> GetOrEmpty(const std::string & key,Args...fallback_keys)68 std::string GetOrEmpty(const std::string& key, Args... fallback_keys) const { 69 return Get(key, fallback_keys..., /*default_value=*/""); 70 } 71 72 // Returns the current value of the boolean system property `key`, or `default_value` if the 73 // property doesn't have a value. See `android::base::ParseBool` for how the value is parsed. GetBool(const std::string & key,bool default_value)74 bool GetBool(const std::string& key, bool default_value) const { 75 android::base::ParseBoolResult result = android::base::ParseBool(GetProperty(key)); 76 if (result != android::base::ParseBoolResult::kError) { 77 return result == android::base::ParseBoolResult::kTrue; 78 } 79 return default_value; 80 } 81 82 // Same as above, but allows specifying one or more fallback keys. The last argument is a bool 83 // default value that will be used if none of the given keys has a value. 84 // 85 // Usage: 86 // 87 // Look up for "key_1", then "key_2", then "key_3". If none of them has a value, return true: 88 // Get("key_1", "key_2", "key_3", /*default_value=*/true) 89 template <typename... Args> GetBool(const std::string & key,const std::string & fallback_key,Args...args)90 bool GetBool(const std::string& key, const std::string& fallback_key, Args... args) const { 91 return GetBool(key, GetBool(fallback_key, args...)); 92 } 93 94 protected: 95 // The single source of truth of system properties. Can be mocked in unit tests. GetProperty(const std::string & key)96 virtual std::string GetProperty(const std::string& key) const { 97 return android::base::GetProperty(key, /*default_value=*/""); 98 } 99 }; 100 101 } // namespace tools 102 } // namespace art 103 104 #endif // ART_LIBARTTOOLS_TOOLS_SYSTEM_PROPERTIES_H_ 105