summaryrefslogtreecommitdiffstats
path: root/ipc/chromium/src/base/task.h
blob: 9b1ae7feffba10d13e73b568d4e3051a84780130 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_TASK_H_
#define BASE_TASK_H_

#include "base/revocable_store.h"
#include "base/tuple.h"

#include "nsISupportsImpl.h"
#include "nsThreadUtils.h"

#include <type_traits>
#include <utility>

// Helper functions so that we can call a function a pass it arguments that come
// from a Tuple.

namespace details {

// Call the given method on the given object. Arguments are passed by move
// semantics from the given tuple. If the tuple has length N, the sequence must
// be IndexSequence<0, 1, ..., N-1>.
template <size_t... Indices, class ObjT, class Method, typename... Args>
void CallMethod(std::index_sequence<Indices...>, ObjT* obj, Method method,
                std::tuple<Args...>& arg) {
  (obj->*method)(std::move(std::get<Indices>(arg))...);
}

// Same as above, but call a function.
template <size_t... Indices, typename Function, typename... Args>
void CallFunction(std::index_sequence<Indices...>, Function function,
                  std::tuple<Args...>& arg) {
  (*function)(std::move(std::get<Indices>(arg))...);
}

}  // namespace details

// Call a method on the given object. Arguments are passed by move semantics
// from the given tuple.
template <class ObjT, class Method, typename... Args>
void DispatchTupleToMethod(ObjT* obj, Method method, std::tuple<Args...>& arg) {
  details::CallMethod(std::index_sequence_for<Args...>{}, obj, method, arg);
}

// Same as above, but call a function.
template <typename Function, typename... Args>
void DispatchTupleToFunction(Function function, std::tuple<Args...>& arg) {
  details::CallFunction(std::index_sequence_for<Args...>{}, function, arg);
}

// General task implementations ------------------------------------------------

// Task to delete an object
template <class T>
class DeleteTask : public mozilla::CancelableRunnable {
 public:
  explicit DeleteTask(T* obj)
      : mozilla::CancelableRunnable("DeleteTask"), obj_(obj) {}
  NS_IMETHOD Run() override {
    delete obj_;
    return NS_OK;
  }
  virtual nsresult Cancel() override {
    obj_ = NULL;
    return NS_OK;
  }

 private:
  T* MOZ_UNSAFE_REF(
      "The validity of this pointer must be enforced by "
      "external factors.") obj_;
};

// RunnableMethodTraits --------------------------------------------------------
//
// This traits-class is used by RunnableMethod to manage the lifetime of the
// callee object.  By default, it is assumed that the callee supports AddRef
// and Release methods.  A particular class can specialize this template to
// define other lifetime management.  For example, if the callee is known to
// live longer than the RunnableMethod object, then a RunnableMethodTraits
// struct could be defined with empty RetainCallee and ReleaseCallee methods.

template <class T>
struct RunnableMethodTraits {
  static void RetainCallee(T* obj) { obj->AddRef(); }
  static void ReleaseCallee(T* obj) { obj->Release(); }
};

// This allows using the NewRunnableMethod() functions with a const pointer
// to the callee object. See the similar support in nsRefPtr for a rationale
// of why this is reasonable.
template <class T>
struct RunnableMethodTraits<const T> {
  static void RetainCallee(const T* obj) { const_cast<T*>(obj)->AddRef(); }
  static void ReleaseCallee(const T* obj) { const_cast<T*>(obj)->Release(); }
};

// RunnableMethod and RunnableFunction -----------------------------------------
//
// Runnable methods are a type of task that call a function on an object when
// they are run. We implement both an object and a set of NewRunnableMethod and
// NewRunnableFunction functions for convenience. These functions are
// overloaded and will infer the template types, simplifying calling code.
//
// The template definitions all use the following names:
// T                - the class type of the object you're supplying
//                    this is not needed for the Static version of the call
// Method/Function  - the signature of a pointer to the method or function you
//                    want to call
// Param            - the parameter(s) to the method, possibly packed as a Tuple
// A                - the first parameter (if any) to the method
// B                - the second parameter (if any) to the mathod
//
// Put these all together and you get an object that can call a method whose
// signature is:
//   R T::MyFunction([A[, B]])
//
// Usage:
// PostTask(NewRunnableMethod(object, &Object::method[, a[, b]])
// PostTask(NewRunnableFunction(&function[, a[, b]])

// RunnableMethod and NewRunnableMethod implementation -------------------------

template <class T, class Method, class Params>
class RunnableMethod : public mozilla::CancelableRunnable,
                       public RunnableMethodTraits<T> {
 public:
  RunnableMethod(T* obj, Method meth, Params&& params)
      : mozilla::CancelableRunnable("RunnableMethod"),
        obj_(obj),
        meth_(meth),
        params_(std::forward<Params>(params)) {
    this->RetainCallee(obj_);
  }
  ~RunnableMethod() { ReleaseCallee(); }

  NS_IMETHOD Run() override {
    if (obj_) DispatchTupleToMethod(obj_, meth_, params_);
    return NS_OK;
  }

  virtual nsresult Cancel() override {
    ReleaseCallee();
    return NS_OK;
  }

 private:
  void ReleaseCallee() {
    if (obj_) {
      RunnableMethodTraits<T>::ReleaseCallee(obj_);
      obj_ = nullptr;
    }
  }

  // This is owning because of the RetainCallee and ReleaseCallee calls in the
  // constructor and destructor.
  T* MOZ_OWNING_REF obj_;
  Method meth_;
  Params params_;
};

namespace dont_add_new_uses_of_this {

// Don't add new uses of this!!!!
template <class T, class Method, typename... Args>
inline already_AddRefed<mozilla::Runnable> NewRunnableMethod(T* object,
                                                             Method method,
                                                             Args&&... args) {
  typedef std::tuple<std::decay_t<Args>...> ArgsTuple;
  RefPtr<mozilla::Runnable> t = new RunnableMethod<T, Method, ArgsTuple>(
      object, method, std::make_tuple(std::forward<Args>(args)...));
  return t.forget();
}

}  // namespace dont_add_new_uses_of_this

// RunnableFunction and NewRunnableFunction implementation ---------------------

template <class Function, class Params>
class RunnableFunction : public mozilla::CancelableRunnable {
 public:
  RunnableFunction(const char* name, Function function, Params&& params)
      : mozilla::CancelableRunnable(name),
        function_(function),
        params_(std::forward<Params>(params)) {}

  ~RunnableFunction() {}

  NS_IMETHOD Run() override {
    if (function_) DispatchTupleToFunction(function_, params_);
    return NS_OK;
  }

  virtual nsresult Cancel() override {
    function_ = nullptr;
    return NS_OK;
  }

  Function function_;
  Params params_;
};

template <class Function, typename... Args>
inline already_AddRefed<mozilla::CancelableRunnable>
NewCancelableRunnableFunction(const char* name, Function function,
                              Args&&... args) {
  typedef std::tuple<std::decay_t<Args>...> ArgsTuple;
  RefPtr<mozilla::CancelableRunnable> t =
      new RunnableFunction<Function, ArgsTuple>(
          name, function, std::make_tuple(std::forward<Args>(args)...));
  return t.forget();
}

template <class Function, typename... Args>
inline already_AddRefed<mozilla::Runnable> NewRunnableFunction(
    const char* name, Function function, Args&&... args) {
  typedef std::tuple<std::decay_t<Args>...> ArgsTuple;
  RefPtr<mozilla::Runnable> t = new RunnableFunction<Function, ArgsTuple>(
      name, function, std::make_tuple(std::forward<Args>(args)...));
  return t.forget();
}

#endif  // BASE_TASK_H_