auto_testing_hook.h revision 5821806d5e7f356e8fa4b058a389a808ea183019 
1// Copyright (c) 2010 The Chromium Authors. All rights reserved.
2//
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4// modification, are permitted provided that the following conditions are
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6//
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16//
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28//
29// Utility for using SideStep with unit tests.
30
31#ifndef CEEE_TESTING_SIDESTEP_AUTO_TESTING_HOOK_H_
32#define CEEE_TESTING_SIDESTEP_AUTO_TESTING_HOOK_H_
33
34#include "base/basictypes.h"
35#include "base/logging.h"
36#include "preamble_patcher.h"
37
38#define SIDESTEP_CHK(x)  CHECK(x)
39#define SIDESTEP_EXPECT_TRUE(x)  SIDESTEP_CHK(x)
40
41namespace sidestep {
42
43// Same trick as common/scope_cleanup.h ScopeGuardImplBase
44class AutoTestingHookBase {
45 public:
46  virtual ~AutoTestingHookBase() {}
47};
48
49// This is the typedef you normally use for the class, e.g.
50//
51// AutoTestingHook hook = MakeTestingHook(TargetFunc, HookTargetFunc);
52//
53// The 'hook' variable will then be destroyed when it goes out of scope.
54//
55// NOTE: You must not hold this type as a member of another class.  Its
56// destructor will not get called.
57typedef const AutoTestingHookBase& AutoTestingHook;
58
59// This is the class you must use when holding a hook as a member of another
60// class, e.g.
61//
62// public:
63//  AutoTestingHookHolder holder_;
64//  MyClass() : my_hook_holder(MakeTestingHookHolder(Target, Hook)) {}
65class AutoTestingHookHolder {
66 public:
67  explicit AutoTestingHookHolder(AutoTestingHookBase* hook) : hook_(hook) {}
68  ~AutoTestingHookHolder() { delete hook_; }
69 private:
70  AutoTestingHookHolder() {}  // disallow
71  AutoTestingHookBase* hook_;
72};
73
74// This class helps patch a function, then unpatch it when the object exits
75// scope, and also maintains the pointer to the original function stub.
76//
77// To enable use of the class without having to explicitly provide the
78// type of the function pointers (and instead only providing it
79// implicitly) we use the same trick as ScopeGuard (see
80// common/scope_cleanup.h) uses, so to create a hook you use the MakeHook
81// function rather than a constructor.
82//
83// NOTE:  This function is only safe for e.g. unit tests and _not_ for
84// production code.  See PreamblePatcher class for details.
85template <typename T>
86class AutoTestingHookImpl : public AutoTestingHookBase {
87 public:
88  static AutoTestingHookImpl<T> MakeTestingHook(T target_function,
89                                                T replacement_function,
90                                                bool do_it) {
91    return AutoTestingHookImpl<T>(target_function, replacement_function, do_it);
92  }
93
94  static AutoTestingHookImpl<T>* MakeTestingHookHolder(T target_function,
95                                                       T replacement_function,
96                                                       bool do_it) {
97    return new AutoTestingHookImpl<T>(target_function,
98                                      replacement_function, do_it);
99  }
100
101  ~AutoTestingHookImpl() {
102    if (did_it_) {
103      SIDESTEP_CHK(SIDESTEP_SUCCESS == PreamblePatcher::Unpatch(
104          (void*)target_function_, (void*)replacement_function_,
105          (void*)original_function_));
106    }
107  }
108
109  // Returns a pointer to the original function.  To use this method you will
110  // have to explicitly create an AutoTestingHookImpl of the specific
111  // function pointer type (i.e. not use the AutoTestingHook typedef).
112  T original_function() {
113    return original_function_;
114  }
115
116 private:
117  AutoTestingHookImpl(T target_function, T replacement_function, bool do_it)
118      : target_function_(target_function),
119        original_function_(NULL),
120        replacement_function_(replacement_function),
121        did_it_(do_it) {
122    if (do_it) {
123      SIDESTEP_CHK(SIDESTEP_SUCCESS == PreamblePatcher::Patch(target_function,
124                                                     replacement_function,
125                                                     &original_function_));
126    }
127  }
128
129  T target_function_;  // always valid
130  T original_function_;  // always valid
131  T replacement_function_;  // always valid
132  bool did_it_;  // Remember if we did it or not...
133};
134
135template <typename T>
136inline AutoTestingHookImpl<T> MakeTestingHook(T target,
137                                              T replacement,
138                                              bool do_it) {
139  return AutoTestingHookImpl<T>::MakeTestingHook(target, replacement, do_it);
140}
141
142template <typename T>
143inline AutoTestingHookImpl<T> MakeTestingHook(T target, T replacement) {
144  return AutoTestingHookImpl<T>::MakeTestingHook(target, replacement, true);
145}
146
147template <typename T>
148inline AutoTestingHookImpl<T>* MakeTestingHookHolder(T target, T replacement) {
149  return AutoTestingHookImpl<T>::MakeTestingHookHolder(target, replacement,
150                                                       true);
151}
152
153};  // namespace sidestep
154
155#endif  // CEEE_TESTING_SIDESTEP_AUTO_TESTING_HOOK_H_
156