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 45namespace chromeos_update_engine { 46 47// Used by Actions an InputObjectType or OutputObjectType to specify that 48// for that type, no object is taken/given. 49class NoneType {}; 50 51template<typename T> 52class Action; 53 54template<typename ObjectType> 55class 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 90template<typename FromAction, typename ToAction> 91void 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