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rspangler@google.com49fdf182009-10-10 00:57:34 +00001// Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
Gilad Arnoldcf175a02014-07-10 16:48:47 -07005#ifndef UPDATE_ENGINE_ACTION_PIPE_H_
6#define UPDATE_ENGINE_ACTION_PIPE_H_
rspangler@google.com49fdf182009-10-10 00:57:34 +00007
8#include <stdio.h>
Alex Deymobc91a272014-05-20 16:45:33 -07009
rspangler@google.com49fdf182009-10-10 00:57:34 +000010#include <map>
Alex Deymobc91a272014-05-20 16:45:33 -070011#include <memory>
rspangler@google.com49fdf182009-10-10 00:57:34 +000012#include <string>
Alex Deymobc91a272014-05-20 16:45:33 -070013
Alex Deymobc91a272014-05-20 16:45:33 -070014#include <base/logging.h>
Ben Chan05735a12014-09-03 07:48:22 -070015#include <base/macros.h>
rspangler@google.com49fdf182009-10-10 00:57:34 +000016
17// The structure of these classes (Action, ActionPipe, ActionProcessor, etc.)
18// is based on the KSAction* classes from the Google Update Engine code at
19// http://code.google.com/p/update-engine/ . The author of this file sends
20// a big thanks to that team for their high quality design, implementation,
21// and documentation.
22
23// This class serves as a temporary holding area for an object passed out
24// from one Action and into another Action. It's templated so that it may
25// contain any type of object that an Action outputs/inputs. Actions
26// cannot be bonded (i.e., connected with a pipe) if their output/input
27// object types differ (a compiler error will result).
28//
29// An ActionPipe is generally created with the Bond() method and owned by
30// the two Action objects. a shared_ptr is used so that when the last Action
31// pointing to an ActionPipe dies, the ActionPipe dies, too.
32
rspangler@google.com49fdf182009-10-10 00:57:34 +000033namespace chromeos_update_engine {
34
35// Used by Actions an InputObjectType or OutputObjectType to specify that
36// for that type, no object is taken/given.
37class NoneType {};
38
39template<typename T>
40class Action;
41
42template<typename ObjectType>
43class ActionPipe {
44 public:
Darin Petkovfbb40092010-07-29 17:05:50 -070045 virtual ~ActionPipe() {}
rspangler@google.com49fdf182009-10-10 00:57:34 +000046
47 // This should be called by an Action on its input pipe.
48 // Returns a reference to the stored object.
49 const ObjectType& contents() const { return contents_; }
50
51 // This should be called by an Action on its output pipe.
52 // Stores a copy of the passed object in this pipe.
53 void set_contents(const ObjectType& contents) { contents_ = contents; }
54
55 // Bonds two Actions together with a new ActionPipe. The ActionPipe is
56 // jointly owned by the two Actions and will be automatically destroyed
57 // when the last Action is destroyed.
58 template<typename FromAction, typename ToAction>
59 static void Bond(FromAction* from, ToAction* to) {
Ben Chanf9cb98c2014-09-21 18:31:30 -070060 std::shared_ptr<ActionPipe<ObjectType>> pipe(new ActionPipe<ObjectType>);
rspangler@google.com49fdf182009-10-10 00:57:34 +000061 from->set_out_pipe(pipe);
62
63 to->set_in_pipe(pipe); // If you get an error on this line, then
64 // it most likely means that the From object's OutputObjectType is
65 // different from the To object's InputObjectType.
66 }
67
68 private:
69 ObjectType contents_;
70
71 // The ctor is private. This is because this class should construct itself
72 // via the static Bond() method.
73 ActionPipe() {}
74 DISALLOW_COPY_AND_ASSIGN(ActionPipe);
75};
76
77// Utility function
78template<typename FromAction, typename ToAction>
79void BondActions(FromAction* from, ToAction* to) {
80 // TODO(adlr): find something like this that the compiler accepts:
81 // COMPILE_ASSERT(typeof(typename FromAction::OutputObjectType) ==
82 // typeof(typename ToAction::InputObjectType),
83 // FromAction_OutputObjectType_doesnt_match_ToAction_InputObjectType);
84 ActionPipe<typename FromAction::OutputObjectType>::Bond(from, to);
85}
86
87} // namespace chromeos_update_engine
88
Gilad Arnoldcf175a02014-07-10 16:48:47 -070089#endif // UPDATE_ENGINE_ACTION_PIPE_H_