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// Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <stdio.h>
#include <iostream>
#include <map>
#include <string>
#include <tr1/memory>
#include "base/basictypes.h"
#include "base/logging.h"
// The structure of these classes (Action, ActionPipe, ActionProcessor, etc.)
// is based on the KSAction* classes from the Google Update Engine code at
// . 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 {
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::tr1::shared_ptr<ActionPipe<ObjectType> > pipe(
new ActionPipe<ObjectType>);
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.
ObjectType contents_;
// The ctor is private. This is because this class should construct itself
// via the static Bond() method.
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