summaryrefslogtreecommitdiffstats
path: root/base/callback.h
blob: 7f2eb706a05293ddf3a9ccc6bec267d9eea60d42 (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
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
// Copyright (c) 2010 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_CALLBACK_H_
#define BASE_CALLBACK_H_
#pragma once

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

// Callback --------------------------------------------------------------------
//
// A Callback is like a Task but with unbound parameters. It is basically an
// object-oriented function pointer.
//
// Callbacks are designed to work with Tuples.  A set of helper functions and
// classes is provided to hide the Tuple details from the consumer.  Client
// code will generally work with the CallbackRunner base class, which merely
// provides a Run method and is returned by the New* functions. This allows
// users to not care which type of class implements the callback, only that it
// has a certain number and type of arguments.
//
// The implementation of this is done by CallbackImpl, which inherits
// CallbackStorage to store the data. This allows the storage of the data
// (requiring the class type T) to be hidden from users, who will want to call
// this regardless of the implementor's type T.
//
// Note that callbacks currently have no facility for cancelling or abandoning
// them. We currently handle this at a higher level for cases where this is
// necessary. The pointer in a callback must remain valid until the callback
// is made.
//
// Like Task, the callback executor is responsible for deleting the callback
// pointer once the callback has executed.
//
// Example client usage:
//   void Object::DoStuff(int, string);
//   Callback2<int, string>::Type* callback =
//       NewCallback(obj, &Object::DoStuff);
//   callback->Run(5, string("hello"));
//   delete callback;
// or, equivalently, using tuples directly:
//   CallbackRunner<Tuple2<int, string> >* callback =
//       NewCallback(obj, &Object::DoStuff);
//   callback->RunWithParams(MakeTuple(5, string("hello")));
//
// There is also a 0-args version that returns a value.  Example:
//   int Object::GetNextInt();
//   CallbackWithReturnValue<int>::Type* callback =
//       NewCallbackWithReturnValue(obj, &Object::GetNextInt);
//   int next_int = callback->Run();
//   delete callback;

// Base for all Callbacks that handles storage of the pointers.
template <class T, typename Method>
class CallbackStorage {
 public:
  CallbackStorage(T* obj, Method meth) : obj_(obj), meth_(meth) {
  }

 protected:
  T* obj_;
  Method meth_;
};

// Interface that is exposed to the consumer, that does the actual calling
// of the method.
template <typename Params>
class CallbackRunner {
 public:
  typedef Params TupleType;

  virtual ~CallbackRunner() {}
  virtual void RunWithParams(const Params& params) = 0;

  // Convenience functions so callers don't have to deal with Tuples.
  inline void Run() {
    RunWithParams(Tuple0());
  }

  template <typename Arg1>
  inline void Run(const Arg1& a) {
    RunWithParams(Params(a));
  }

  template <typename Arg1, typename Arg2>
  inline void Run(const Arg1& a, const Arg2& b) {
    RunWithParams(Params(a, b));
  }

  template <typename Arg1, typename Arg2, typename Arg3>
  inline void Run(const Arg1& a, const Arg2& b, const Arg3& c) {
    RunWithParams(Params(a, b, c));
  }

  template <typename Arg1, typename Arg2, typename Arg3, typename Arg4>
  inline void Run(const Arg1& a, const Arg2& b, const Arg3& c, const Arg4& d) {
    RunWithParams(Params(a, b, c, d));
  }

  template <typename Arg1, typename Arg2, typename Arg3,
            typename Arg4, typename Arg5>
  inline void Run(const Arg1& a, const Arg2& b, const Arg3& c,
                  const Arg4& d, const Arg5& e) {
    RunWithParams(Params(a, b, c, d, e));
  }
};

template <class T, typename Method, typename Params>
class CallbackImpl : public CallbackStorage<T, Method>,
                     public CallbackRunner<Params> {
 public:
  CallbackImpl(T* obj, Method meth) : CallbackStorage<T, Method>(obj, meth) {
  }
  virtual void RunWithParams(const Params& params) {
    // use "this->" to force C++ to look inside our templatized base class; see
    // Effective C++, 3rd Ed, item 43, p210 for details.
    DispatchToMethod(this->obj_, this->meth_, params);
  }
};

// 0-arg implementation
struct Callback0 {
  typedef CallbackRunner<Tuple0> Type;
};

template <class T>
typename Callback0::Type* NewCallback(T* object, void (T::*method)()) {
  return new CallbackImpl<T, void (T::*)(), Tuple0 >(object, method);
}

// 1-arg implementation
template <typename Arg1>
struct Callback1 {
  typedef CallbackRunner<Tuple1<Arg1> > Type;
};

template <class T, typename Arg1>
typename Callback1<Arg1>::Type* NewCallback(T* object,
                                            void (T::*method)(Arg1)) {
  return new CallbackImpl<T, void (T::*)(Arg1), Tuple1<Arg1> >(object, method);
}

// 2-arg implementation
template <typename Arg1, typename Arg2>
struct Callback2 {
  typedef CallbackRunner<Tuple2<Arg1, Arg2> > Type;
};

template <class T, typename Arg1, typename Arg2>
typename Callback2<Arg1, Arg2>::Type* NewCallback(
    T* object,
    void (T::*method)(Arg1, Arg2)) {
  return new CallbackImpl<T, void (T::*)(Arg1, Arg2),
      Tuple2<Arg1, Arg2> >(object, method);
}

// 3-arg implementation
template <typename Arg1, typename Arg2, typename Arg3>
struct Callback3 {
  typedef CallbackRunner<Tuple3<Arg1, Arg2, Arg3> > Type;
};

template <class T, typename Arg1, typename Arg2, typename Arg3>
typename Callback3<Arg1, Arg2, Arg3>::Type* NewCallback(
    T* object,
    void (T::*method)(Arg1, Arg2, Arg3)) {
  return new CallbackImpl<T,  void (T::*)(Arg1, Arg2, Arg3),
      Tuple3<Arg1, Arg2, Arg3> >(object, method);
}

// 4-arg implementation
template <typename Arg1, typename Arg2, typename Arg3, typename Arg4>
struct Callback4 {
  typedef CallbackRunner<Tuple4<Arg1, Arg2, Arg3, Arg4> > Type;
};

template <class T, typename Arg1, typename Arg2, typename Arg3, typename Arg4>
typename Callback4<Arg1, Arg2, Arg3, Arg4>::Type* NewCallback(
    T* object,
    void (T::*method)(Arg1, Arg2, Arg3, Arg4)) {
  return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3, Arg4),
      Tuple4<Arg1, Arg2, Arg3, Arg4> >(object, method);
}

// 5-arg implementation
template <typename Arg1, typename Arg2, typename Arg3,
          typename Arg4, typename Arg5>
struct Callback5 {
  typedef CallbackRunner<Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> > Type;
};

template <class T, typename Arg1, typename Arg2,
          typename Arg3, typename Arg4, typename Arg5>
typename Callback5<Arg1, Arg2, Arg3, Arg4, Arg5>::Type* NewCallback(
    T* object,
    void (T::*method)(Arg1, Arg2, Arg3, Arg4, Arg5)) {
  return new CallbackImpl<T, void (T::*)(Arg1, Arg2, Arg3, Arg4, Arg5),
      Tuple5<Arg1, Arg2, Arg3, Arg4, Arg5> >(object, method);
}

// An UnboundMethod is a wrapper for a method where the actual object is
// provided at Run dispatch time.
template <class T, class Method, class Params>
class UnboundMethod {
 public:
  UnboundMethod(Method m, const Params& p) : m_(m), p_(p) {
    COMPILE_ASSERT((MethodUsesScopedRefptrCorrectly<Method, Params>::value),
                   badunboundmethodparams);
  }
  void Run(T* obj) const {
    DispatchToMethod(obj, m_, p_);
  }
 private:
  Method m_;
  Params p_;
};

// Return value implementation with no args.
template <typename ReturnValue>
struct CallbackWithReturnValue {
  class Type {
   public:
    virtual ~Type() {}
    virtual ReturnValue Run() = 0;
  };
};

template <class T, typename Method, typename ReturnValue>
class CallbackWithReturnValueImpl
    : public CallbackStorage<T, Method>,
      public CallbackWithReturnValue<ReturnValue>::Type {
 public:
  CallbackWithReturnValueImpl(T* obj, Method meth)
      : CallbackStorage<T, Method>(obj, meth) {}

  virtual ReturnValue Run() {
    return (this->obj_->*(this->meth_))();
  }

 protected:
  virtual ~CallbackWithReturnValueImpl() {}
};

template <class T, typename ReturnValue>
typename CallbackWithReturnValue<ReturnValue>::Type*
NewCallbackWithReturnValue(T* object, ReturnValue (T::*method)()) {
  return new CallbackWithReturnValueImpl<T, ReturnValue (T::*)(), ReturnValue>(
      object, method);
}

#endif  // BASE_CALLBACK_H