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101 lines
3.6 KiB
101 lines
3.6 KiB
// |
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// Copyright (C) 2009 The Android Open Source Project |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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// |
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#ifndef UPDATE_ENGINE_COMMON_ACTION_PIPE_H_ |
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#define UPDATE_ENGINE_COMMON_ACTION_PIPE_H_ |
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#include <stdio.h> |
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#include <map> |
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#include <memory> |
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#include <string> |
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#include <base/logging.h> |
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#include <base/macros.h> |
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// The structure of these classes (Action, ActionPipe, ActionProcessor, etc.) |
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// is based on the KSAction* classes from the Google Update Engine code at |
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// http://code.google.com/p/update-engine/ . The author of this file sends |
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// a big thanks to that team for their high quality design, implementation, |
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// and documentation. |
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// This class serves as a temporary holding area for an object passed out |
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// from one Action and into another Action. It's templated so that it may |
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// contain any type of object that an Action outputs/inputs. Actions |
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// cannot be bonded (i.e., connected with a pipe) if their output/input |
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// object types differ (a compiler error will result). |
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// |
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// An ActionPipe is generally created with the Bond() method and owned by |
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// the two Action objects. a shared_ptr is used so that when the last Action |
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// pointing to an ActionPipe dies, the ActionPipe dies, too. |
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namespace chromeos_update_engine { |
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// Used by Actions an InputObjectType or OutputObjectType to specify that |
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// for that type, no object is taken/given. |
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class NoneType {}; |
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template<typename T> |
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class Action; |
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template<typename ObjectType> |
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class ActionPipe { |
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public: |
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virtual ~ActionPipe() {} |
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// This should be called by an Action on its input pipe. |
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// Returns a reference to the stored object. |
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const ObjectType& contents() const { return contents_; } |
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// This should be called by an Action on its output pipe. |
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// Stores a copy of the passed object in this pipe. |
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void set_contents(const ObjectType& contents) { contents_ = contents; } |
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// Bonds two Actions together with a new ActionPipe. The ActionPipe is |
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// jointly owned by the two Actions and will be automatically destroyed |
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// when the last Action is destroyed. |
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template<typename FromAction, typename ToAction> |
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static void Bond(FromAction* from, ToAction* to) { |
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std::shared_ptr<ActionPipe<ObjectType>> pipe(new ActionPipe<ObjectType>); |
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from->set_out_pipe(pipe); |
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to->set_in_pipe(pipe); // If you get an error on this line, then |
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// it most likely means that the From object's OutputObjectType is |
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// different from the To object's InputObjectType. |
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} |
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private: |
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ObjectType contents_; |
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// The ctor is private. This is because this class should construct itself |
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// via the static Bond() method. |
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ActionPipe() {} |
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DISALLOW_COPY_AND_ASSIGN(ActionPipe); |
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}; |
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// Utility function |
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template<typename FromAction, typename ToAction> |
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void BondActions(FromAction* from, ToAction* to) { |
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static_assert( |
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std::is_same<typename FromAction::OutputObjectType, |
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typename ToAction::InputObjectType>::value, |
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"FromAction::OutputObjectType doesn't match ToAction::InputObjectType"); |
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ActionPipe<typename FromAction::OutputObjectType>::Bond(from, to); |
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} |
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} // namespace chromeos_update_engine |
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#endif // UPDATE_ENGINE_COMMON_ACTION_PIPE_H_
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