//
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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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