1 // 2 // Copyright (C) 2009 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_ACTION_PIPE_H_ 18 #define UPDATE_ENGINE_COMMON_ACTION_PIPE_H_ 19 20 #include <stdio.h> 21 22 #include <map> 23 #include <memory> 24 #include <string> 25 26 #include <base/logging.h> 27 #include <base/macros.h> 28 29 // The structure of these classes (Action, ActionPipe, ActionProcessor, etc.) 30 // is based on the KSAction* classes from the Google Update Engine code at 31 // http://code.google.com/p/update-engine/ . The author of this file sends 32 // a big thanks to that team for their high quality design, implementation, 33 // and documentation. 34 35 // This class serves as a temporary holding area for an object passed out 36 // from one Action and into another Action. It's templated so that it may 37 // contain any type of object that an Action outputs/inputs. Actions 38 // cannot be bonded (i.e., connected with a pipe) if their output/input 39 // object types differ (a compiler error will result). 40 // 41 // An ActionPipe is generally created with the Bond() method and owned by 42 // the two Action objects. a shared_ptr is used so that when the last Action 43 // pointing to an ActionPipe dies, the ActionPipe dies, too. 44 45 namespace chromeos_update_engine { 46 47 // Used by Actions an InputObjectType or OutputObjectType to specify that 48 // for that type, no object is taken/given. 49 class NoneType {}; 50 51 template<typename T> 52 class Action; 53 54 template<typename ObjectType> 55 class ActionPipe { 56 public: 57 virtual ~ActionPipe() {} 58 59 // This should be called by an Action on its input pipe. 60 // Returns a reference to the stored object. 61 const ObjectType& contents() const { return contents_; } 62 63 // This should be called by an Action on its output pipe. 64 // Stores a copy of the passed object in this pipe. 65 void set_contents(const ObjectType& contents) { contents_ = contents; } 66 67 // Bonds two Actions together with a new ActionPipe. The ActionPipe is 68 // jointly owned by the two Actions and will be automatically destroyed 69 // when the last Action is destroyed. 70 template<typename FromAction, typename ToAction> 71 static void Bond(FromAction* from, ToAction* to) { 72 std::shared_ptr<ActionPipe<ObjectType>> pipe(new ActionPipe<ObjectType>); 73 from->set_out_pipe(pipe); 74 75 to->set_in_pipe(pipe); // If you get an error on this line, then 76 // it most likely means that the From object's OutputObjectType is 77 // different from the To object's InputObjectType. 78 } 79 80 private: 81 ObjectType contents_; 82 83 // The ctor is private. This is because this class should construct itself 84 // via the static Bond() method. 85 ActionPipe() {} 86 DISALLOW_COPY_AND_ASSIGN(ActionPipe); 87 }; 88 89 // Utility function 90 template<typename FromAction, typename ToAction> 91 void BondActions(FromAction* from, ToAction* to) { 92 static_assert( 93 std::is_same<typename FromAction::OutputObjectType, 94 typename ToAction::InputObjectType>::value, 95 "FromAction::OutputObjectType doesn't match ToAction::InputObjectType"); 96 ActionPipe<typename FromAction::OutputObjectType>::Bond(from, to); 97 } 98 99 } // namespace chromeos_update_engine 100 101 #endif // UPDATE_ENGINE_COMMON_ACTION_PIPE_H_ 102
