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