base/callback.h

   1 // This file was GENERATED by command:
   2 //     pump.py callback.h.pump
   3 // DO NOT EDIT BY HAND!!!
   4
   5
   6 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   7 // Use of this source code is governed by a BSD-style license that can be
   8 // found in the LICENSE file.
   9
  10 #ifndef BASE_CALLBACK_H_
  11 #define BASE_CALLBACK_H_
  12
  13 #include "base/callback_forward.h"
  14 #include "base/callback_internal.h"
  15 #include "base/template_util.h"
  16
  17 // NOTE: Header files that do not require the full definition of Callback or
  18 // Closure should #include "base/callback_forward.h" instead of this file.
  19
  20 // -----------------------------------------------------------------------------
  21 // Introduction
  22 // -----------------------------------------------------------------------------
  23 //
  24 // The templated Callback class is a generalized function object. Together
  25 // with the Bind() function in bind.h, they provide a type-safe method for
  26 // performing partial application of functions.
  27 //
  28 // Partial application (or "currying") is the process of binding a subset of
  29 // a function's arguments to produce another function that takes fewer
  30 // arguments. This can be used to pass around a unit of delayed execution,
  31 // much like lexical closures are used in other languages. For example, it
  32 // is used in Chromium code to schedule tasks on different MessageLoops.
  33 //
  34 // A callback with no unbound input parameters (base::Callback<void(void)>)
  35 // is called a base::Closure. Note that this is NOT the same as what other
  36 // languages refer to as a closure -- it does not retain a reference to its
  37 // enclosing environment.
  38 //
  39 // MEMORY MANAGEMENT AND PASSING
  40 //
  41 // The Callback objects themselves should be passed by const-reference, and
  42 // stored by copy. They internally store their state via a refcounted class
  43 // and thus do not need to be deleted.
  44 //
  45 // The reason to pass via a const-reference is to avoid unnecessary
  46 // AddRef/Release pairs to the internal state.
  47 //
  48 //
  49 // -----------------------------------------------------------------------------
  50 // Quick reference for basic stuff
  51 // -----------------------------------------------------------------------------
  52 //
  53 // BINDING A BARE FUNCTION
  54 //
  55 //   int Return5() { return 5; }
  56 //   base::Callback<int(void)> func_cb = base::Bind(&Return5);
  57 //   LOG(INFO) << func_cb.Run();  // Prints 5.
  58 //
  59 // BINDING A CLASS METHOD
  60 //
  61 //   The first argument to bind is the member function to call, the second is
  62 //   the object on which to call it.
  63 //
  64 //   class Ref : public base::RefCountedThreadSafe<Ref> {
  65 //    public:
  66 //     int Foo() { return 3; }
  67 //     void PrintBye() { LOG(INFO) << "bye."; }
  68 //   };
  69 //   scoped_refptr<Ref> ref = new Ref();
  70 //   base::Callback<void(void)> ref_cb = base::Bind(&Ref::Foo, ref);
  71 //   LOG(INFO) << ref_cb.Run();  // Prints out 3.
  72 //
  73 //   By default the object must support RefCounted or you will get a compiler
  74 //   error. If you're passing between threads, be sure it's
  75 //   RefCountedThreadSafe! See "Advanced binding of member functions" below if
  76 //   you don't want to use reference counting.
  77 //
  78 // RUNNING A CALLBACK
  79 //
  80 //   Callbacks can be run with their "Run" method, which has the same
  81 //   signature as the template argument to the callback.
  82 //
  83 //   void DoSomething(const base::Callback<void(int, std::string)>& callback) {
  84 //     callback.Run(5, "hello");
  85 //   }
  86 //
  87 //   Callbacks can be run more than once (they don't get deleted or marked when
  88 //   run). However, this precludes using base::Passed (see below).
  89 //
  90 //   void DoSomething(const base::Callback<double(double)>& callback) {
  91 //     double myresult = callback.Run(3.14159);
  92 //     myresult += callback.Run(2.71828);
  93 //   }
  94 //
  95 // PASSING UNBOUND INPUT PARAMETERS
  96 //
  97 //   Unbound parameters are specified at the time a callback is Run(). They are
  98 //   specified in the Callback template type:
  99 //
 100 //   void MyFunc(int i, const std::string& str) {}
 101 //   base::Callback<void(int, const std::string&)> cb = base::Bind(&MyFunc);
 102 //   cb.Run(23, "hello, world");
 103 //
 104 // PASSING BOUND INPUT PARAMETERS
 105 //
 106 //   Bound parameters are specified when you create thee callback as arguments
 107 //   to Bind(). They will be passed to the function and the Run()ner of the
 108 //   callback doesn't see those values or even know that the function it's
 109 //   calling.
 110 //
 111 //   void MyFunc(int i, const std::string& str) {}
 112 //   base::Callback<void(void)> cb = base::Bind(&MyFunc, 23, "hello world");
 113 //   cb.Run();
 114 //
 115 //   A callback with no unbound input parameters (base::Callback<void(void)>)
 116 //   is called a base::Closure. So we could have also written:
 117 //
 118 //   base::Closure cb = base::Bind(&MyFunc, 23, "hello world");
 119 //
 120 //   When calling member functions, bound parameters just go after the object
 121 //   pointer.
 122 //
 123 //   base::Closure cb = base::Bind(&MyClass::MyFunc, this, 23, "hello world");
 124 //
 125 // PARTIAL BINDING OF PARAMETERS
 126 //
 127 //   You can specify some parameters when you create the callback, and specify
 128 //   the rest when you execute the callback.
 129 //
 130 //   void MyFunc(int i, const std::string& str) {}
 131 //   base::Callback<void(const std::string&)> cb = base::Bind(&MyFunc, 23);
 132 //   cb.Run("hello world");
 133 //
 134 //   When calling a function bound parameters are first, followed by unbound
 135 //   parameters.
 136 //
 137 //
 138 // -----------------------------------------------------------------------------
 139 // Quick reference for advanced binding
 140 // -----------------------------------------------------------------------------
 141 //
 142 // BINDING A CLASS METHOD WITH WEAK POINTERS
 143 //
 144 //   base::Bind(&MyClass::Foo, GetWeakPtr());
 145 //
 146 //   The callback will not be run if the object has already been destroyed.
 147 //   DANGER: weak pointers are not threadsafe, so don't use this
 148 //   when passing between threads!
 149 //
 150 // BINDING A CLASS METHOD WITH MANUAL LIFETIME MANAGEMENT
 151 //
 152 //   base::Bind(&MyClass::Foo, base::Unretained(this));
 153 //
 154 //   This disables all lifetime management on the object. You're responsible
 155 //   for making sure the object is alive at the time of the call. You break it,
 156 //   you own it!
 157 //
 158 // BINDING A CLASS METHOD AND HAVING THE CALLBACK OWN THE CLASS
 159 //
 160 //   MyClass* myclass = new MyClass;
 161 //   base::Bind(&MyClass::Foo, base::Owned(myclass));
 162 //
 163 //   The object will be deleted when the callback is destroyed, even if it's
 164 //   not run (like if you post a task during shutdown). Potentially useful for
 165 //   "fire and forget" cases.
 166 //
 167 // IGNORING RETURN VALUES
 168 //
 169 //   Sometimes you want to call a function that returns a value in a callback
 170 //   that doesn't expect a return value.
 171 //
 172 //   int DoSomething(int arg) { cout << arg << endl; }
 173 //   base::Callback<void<int>) cb =
 174 //       base::Bind(base::IgnoreResult(&DoSomething));
 175 //
 176 //
 177 // -----------------------------------------------------------------------------
 178 // Quick reference for binding parameters to Bind()
 179 // -----------------------------------------------------------------------------
 180 //
 181 // Bound parameters are specified as arguments to Bind() and are passed to the
 182 // function. A callback with no parameters or no unbound parameters is called a
 183 // Closure (base::Callback<void(void)> and base::Closure are the same thing).
 184 //
 185 // PASSING PARAMETERS OWNED BY THE CALLBACK
 186 //
 187 //   void Foo(int* arg) { cout << *arg << endl; }
 188 //   int* pn = new int(1);
 189 //   base::Closure foo_callback = base::Bind(&foo, base::Owned(pn));
 190 //
 191 //   The parameter will be deleted when the callback is destroyed, even if it's
 192 //   not run (like if you post a task during shutdown).
 193 //
 194 // PASSING PARAMETERS AS A scoped_ptr
 195 //
 196 //   void TakesOwnership(scoped_ptr<Foo> arg) {}
 197 //   scoped_ptr<Foo> f(new Foo);
 198 //   // f becomes null during the following call.
 199 //   base::Closure cb = base::Bind(&TakesOwnership, base::Passed(&f));
 200 //
 201 //   Ownership of the parameter will be with the callback until the it is run,
 202 //   when ownership is passed to the callback function. This means the callback
 203 //   can only be run once. If the callback is never run, it will delete the
 204 //   object when it's destroyed.
 205 //
 206 // PASSING PARAMETERS AS A scoped_refptr
 207 //
 208 //   void TakesOneRef(scoped_refptr<Foo> arg) {}
 209 //   scoped_refptr<Foo> f(new Foo)
 210 //   base::Closure cb = base::Bind(&TakesOneRef, f);
 211 //
 212 //   This should "just work." The closure will take a reference as long as it
 213 //   is alive, and another reference will be taken for the called function.
 214 //
 215 // PASSING PARAMETERS BY REFERENCE
 216 //
 217 //   Const references are *copied* unless ConstRef is used. Example:
 218 //
 219 //   void foo(const int& arg) { printf("%d %p\n", arg, &arg); }
 220 //   int n = 1;
 221 //   base::Closure has_copy = base::Bind(&foo, n);
 222 //   base::Closure has_ref = base::Bind(&foo, base::ConstRef(n));
 223 //   n = 2;
 224 //   foo(n);                        // Prints "2 0xaaaaaaaaaaaa"
 225 //   has_copy.Run();                // Prints "1 0xbbbbbbbbbbbb"
 226 //   has_ref.Run();                 // Prints "2 0xaaaaaaaaaaaa"
 227 //
 228 //   Normally parameters are copied in the closure. DANGER: ConstRef stores a
 229 //   const reference instead, referencing the original parameter. This means
 230 //   that you must ensure the object outlives the callback!
 231 //
 232 //
 233 // -----------------------------------------------------------------------------
 234 // Implementation notes
 235 // -----------------------------------------------------------------------------
 236 //
 237 // WHERE IS THIS DESIGN FROM:
 238 //
 239 // The design Callback and Bind is heavily influenced by C++'s
 240 // tr1::function/tr1::bind, and by the "Google Callback" system used inside
 241 // Google.
 242 //
 243 //
 244 // HOW THE IMPLEMENTATION WORKS:
 245 //
 246 // There are three main components to the system:
 247 //   1) The Callback classes.
 248 //   2) The Bind() functions.
 249 //   3) The arguments wrappers (e.g., Unretained() and ConstRef()).
 250 //
 251 // The Callback classes represent a generic function pointer. Internally,
 252 // it stores a refcounted piece of state that represents the target function
 253 // and all its bound parameters.  Each Callback specialization has a templated
 254 // constructor that takes an BindState<>*.  In the context of the constructor,
 255 // the static type of this BindState<> pointer uniquely identifies the
 256 // function it is representing, all its bound parameters, and a Run() method
 257 // that is capable of invoking the target.
 258 //
 259 // Callback's constructor takes the BindState<>* that has the full static type
 260 // and erases the target function type as well as the types of the bound
 261 // parameters.  It does this by storing a pointer to the specific Run()
 262 // function, and upcasting the state of BindState<>* to a
 263 // BindStateBase*. This is safe as long as this BindStateBase pointer
 264 // is only used with the stored Run() pointer.
 265 //
 266 // To BindState<> objects are created inside the Bind() functions.
 267 // These functions, along with a set of internal templates, are responsible for
 268 //
 269 //  - Unwrapping the function signature into return type, and parameters
 270 //  - Determining the number of parameters that are bound
 271 //  - Creating the BindState storing the bound parameters
 272 //  - Performing compile-time asserts to avoid error-prone behavior
 273 //  - Returning an Callback<> with an arity matching the number of unbound
 274 //    parameters and that knows the correct refcounting semantics for the
 275 //    target object if we are binding a method.
 276 //
 277 // The Bind functions do the above using type-inference, and template
 278 // specializations.
 279 //
 280 // By default Bind() will store copies of all bound parameters, and attempt
 281 // to refcount a target object if the function being bound is a class method.
 282 // These copies are created even if the function takes parameters as const
 283 // references. (Binding to non-const references is forbidden, see bind.h.)
 284 //
 285 // To change this behavior, we introduce a set of argument wrappers
 286 // (e.g., Unretained(), and ConstRef()).  These are simple container templates
 287 // that are passed by value, and wrap a pointer to argument.  See the
 288 // file-level comment in base/bind_helpers.h for more info.
 289 //
 290 // These types are passed to the Unwrap() functions, and the MaybeRefcount()
 291 // functions respectively to modify the behavior of Bind().  The Unwrap()
 292 // and MaybeRefcount() functions change behavior by doing partial
 293 // specialization based on whether or not a parameter is a wrapper type.
 294 //
 295 // ConstRef() is similar to tr1::cref.  Unretained() is specific to Chromium.
 296 //
 297 //
 298 // WHY NOT TR1 FUNCTION/BIND?
 299 //
 300 // Direct use of tr1::function and tr1::bind was considered, but ultimately
 301 // rejected because of the number of copy constructors invocations involved
 302 // in the binding of arguments during construction, and the forwarding of
 303 // arguments during invocation.  These copies will no longer be an issue in
 304 // C++0x because C++0x will support rvalue reference allowing for the compiler
 305 // to avoid these copies.  However, waiting for C++0x is not an option.
 306 //
 307 // Measured with valgrind on gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5), the
 308 // tr1::bind call itself will invoke a non-trivial copy constructor three times
 309 // for each bound parameter.  Also, each when passing a tr1::function, each
 310 // bound argument will be copied again.
 311 //
 312 // In addition to the copies taken at binding and invocation, copying a
 313 // tr1::function causes a copy to be made of all the bound parameters and
 314 // state.
 315 //
 316 // Furthermore, in Chromium, it is desirable for the Callback to take a
 317 // reference on a target object when representing a class method call.  This
 318 // is not supported by tr1.
 319 //
 320 // Lastly, tr1::function and tr1::bind has a more general and flexible API.
 321 // This includes things like argument reordering by use of
 322 // tr1::bind::placeholder, support for non-const reference parameters, and some
 323 // limited amount of subtyping of the tr1::function object (e.g.,
 324 // tr1::function<int(int)> is convertible to tr1::function<void(int)>).
 325 //
 326 // These are not features that are required in Chromium. Some of them, such as
 327 // allowing for reference parameters, and subtyping of functions, may actually
 328 // become a source of errors. Removing support for these features actually
 329 // allows for a simpler implementation, and a terser Currying API.
 330 //
 331 //
 332 // WHY NOT GOOGLE CALLBACKS?
 333 //
 334 // The Google callback system also does not support refcounting.  Furthermore,
 335 // its implementation has a number of strange edge cases with respect to type
 336 // conversion of its arguments.  In particular, the argument's constness must
 337 // at times match exactly the function signature, or the type-inference might
 338 // break.  Given the above, writing a custom solution was easier.
 339 //
 340 //
 341 // MISSING FUNCTIONALITY
 342 //  - Invoking the return of Bind.  Bind(&foo).Run() does not work;
 343 //  - Binding arrays to functions that take a non-const pointer.
 344 //    Example:
 345 //      void Foo(const char* ptr);
 346 //      void Bar(char* ptr);
 347 //      Bind(&Foo, "test");
 348 //      Bind(&Bar, "test");  // This fails because ptr is not const.
 349
 350 namespace base {
 351
 352 // First, we forward declare the Callback class template. This informs the
 353 // compiler that the template only has 1 type parameter which is the function
 354 // signature that the Callback is representing.
 355 //
 356 // After this, create template specializations for 0-7 parameters. Note that
 357 // even though the template typelist grows, the specialization still
 358 // only has one type: the function signature.
 359 //
 360 // If you are thinking of forward declaring Callback in your own header file,
 361 // please include "base/callback_forward.h" instead.
 362 template <typename Sig>
 363 class Callback;
 364
 365 namespace internal {
 366 template <typename Runnable, typename RunType, typename BoundArgsType>
 367 struct BindState;
 368 }  // namespace internal
 369
 370 template <typename R>
 371 class Callback<R(void)> : public internal::CallbackBase {
 372  public:
 373   typedef R(RunType)();
 374
 375   Callback() : CallbackBase(NULL) { }
 376
 377   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 378   // return the exact Callback<> type.  See base/bind.h for details.
 379   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 380   Callback(internal::BindState<Runnable, BindRunType,
 381            BoundArgsType>* bind_state)
 382       : CallbackBase(bind_state) {
 383
 384     // Force the assignment to a local variable of PolymorphicInvoke
 385     // so the compiler will typecheck that the passed in Run() method has
 386     // the correct type.
 387     PolymorphicInvoke invoke_func =
 388         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 389             ::InvokerType::Run;
 390     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 391   }
 392
 393   bool Equals(const Callback& other) const {
 394     return CallbackBase::Equals(other);
 395   }
 396
 397   R Run() const {
 398     PolymorphicInvoke f =
 399         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 400
 401     return f(bind_state_.get());
 402   }
 403
 404  private:
 405   typedef R(*PolymorphicInvoke)(
 406       internal::BindStateBase*);
 407
 408 };
 409
 410 template <typename R, typename A1>
 411 class Callback<R(A1)> : public internal::CallbackBase {
 412  public:
 413   typedef R(RunType)(A1);
 414
 415   Callback() : CallbackBase(NULL) { }
 416
 417   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 418   // return the exact Callback<> type.  See base/bind.h for details.
 419   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 420   Callback(internal::BindState<Runnable, BindRunType,
 421            BoundArgsType>* bind_state)
 422       : CallbackBase(bind_state) {
 423
 424     // Force the assignment to a local variable of PolymorphicInvoke
 425     // so the compiler will typecheck that the passed in Run() method has
 426     // the correct type.
 427     PolymorphicInvoke invoke_func =
 428         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 429             ::InvokerType::Run;
 430     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 431   }
 432
 433   bool Equals(const Callback& other) const {
 434     return CallbackBase::Equals(other);
 435   }
 436
 437   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1) const {
 438     PolymorphicInvoke f =
 439         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 440
 441     return f(bind_state_.get(), internal::CallbackForward(a1));
 442   }
 443
 444  private:
 445   typedef R(*PolymorphicInvoke)(
 446       internal::BindStateBase*,
 447           typename internal::CallbackParamTraits<A1>::ForwardType);
 448
 449 };
 450
 451 template <typename R, typename A1, typename A2>
 452 class Callback<R(A1, A2)> : public internal::CallbackBase {
 453  public:
 454   typedef R(RunType)(A1, A2);
 455
 456   Callback() : CallbackBase(NULL) { }
 457
 458   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 459   // return the exact Callback<> type.  See base/bind.h for details.
 460   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 461   Callback(internal::BindState<Runnable, BindRunType,
 462            BoundArgsType>* bind_state)
 463       : CallbackBase(bind_state) {
 464
 465     // Force the assignment to a local variable of PolymorphicInvoke
 466     // so the compiler will typecheck that the passed in Run() method has
 467     // the correct type.
 468     PolymorphicInvoke invoke_func =
 469         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 470             ::InvokerType::Run;
 471     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 472   }
 473
 474   bool Equals(const Callback& other) const {
 475     return CallbackBase::Equals(other);
 476   }
 477
 478   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 479         typename internal::CallbackParamTraits<A2>::ForwardType a2) const {
 480     PolymorphicInvoke f =
 481         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 482
 483     return f(bind_state_.get(), internal::CallbackForward(a1),
 484              internal::CallbackForward(a2));
 485   }
 486
 487  private:
 488   typedef R(*PolymorphicInvoke)(
 489       internal::BindStateBase*,
 490           typename internal::CallbackParamTraits<A1>::ForwardType,
 491           typename internal::CallbackParamTraits<A2>::ForwardType);
 492
 493 };
 494
 495 template <typename R, typename A1, typename A2, typename A3>
 496 class Callback<R(A1, A2, A3)> : public internal::CallbackBase {
 497  public:
 498   typedef R(RunType)(A1, A2, A3);
 499
 500   Callback() : CallbackBase(NULL) { }
 501
 502   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 503   // return the exact Callback<> type.  See base/bind.h for details.
 504   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 505   Callback(internal::BindState<Runnable, BindRunType,
 506            BoundArgsType>* bind_state)
 507       : CallbackBase(bind_state) {
 508
 509     // Force the assignment to a local variable of PolymorphicInvoke
 510     // so the compiler will typecheck that the passed in Run() method has
 511     // the correct type.
 512     PolymorphicInvoke invoke_func =
 513         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 514             ::InvokerType::Run;
 515     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 516   }
 517
 518   bool Equals(const Callback& other) const {
 519     return CallbackBase::Equals(other);
 520   }
 521
 522   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 523         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 524         typename internal::CallbackParamTraits<A3>::ForwardType a3) const {
 525     PolymorphicInvoke f =
 526         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 527
 528     return f(bind_state_.get(), internal::CallbackForward(a1),
 529              internal::CallbackForward(a2),
 530              internal::CallbackForward(a3));
 531   }
 532
 533  private:
 534   typedef R(*PolymorphicInvoke)(
 535       internal::BindStateBase*,
 536           typename internal::CallbackParamTraits<A1>::ForwardType,
 537           typename internal::CallbackParamTraits<A2>::ForwardType,
 538           typename internal::CallbackParamTraits<A3>::ForwardType);
 539
 540 };
 541
 542 template <typename R, typename A1, typename A2, typename A3, typename A4>
 543 class Callback<R(A1, A2, A3, A4)> : public internal::CallbackBase {
 544  public:
 545   typedef R(RunType)(A1, A2, A3, A4);
 546
 547   Callback() : CallbackBase(NULL) { }
 548
 549   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 550   // return the exact Callback<> type.  See base/bind.h for details.
 551   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 552   Callback(internal::BindState<Runnable, BindRunType,
 553            BoundArgsType>* bind_state)
 554       : CallbackBase(bind_state) {
 555
 556     // Force the assignment to a local variable of PolymorphicInvoke
 557     // so the compiler will typecheck that the passed in Run() method has
 558     // the correct type.
 559     PolymorphicInvoke invoke_func =
 560         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 561             ::InvokerType::Run;
 562     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 563   }
 564
 565   bool Equals(const Callback& other) const {
 566     return CallbackBase::Equals(other);
 567   }
 568
 569   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 570         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 571         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 572         typename internal::CallbackParamTraits<A4>::ForwardType a4) const {
 573     PolymorphicInvoke f =
 574         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 575
 576     return f(bind_state_.get(), internal::CallbackForward(a1),
 577              internal::CallbackForward(a2),
 578              internal::CallbackForward(a3),
 579              internal::CallbackForward(a4));
 580   }
 581
 582  private:
 583   typedef R(*PolymorphicInvoke)(
 584       internal::BindStateBase*,
 585           typename internal::CallbackParamTraits<A1>::ForwardType,
 586           typename internal::CallbackParamTraits<A2>::ForwardType,
 587           typename internal::CallbackParamTraits<A3>::ForwardType,
 588           typename internal::CallbackParamTraits<A4>::ForwardType);
 589
 590 };
 591
 592 template <typename R, typename A1, typename A2, typename A3, typename A4,
 593     typename A5>
 594 class Callback<R(A1, A2, A3, A4, A5)> : public internal::CallbackBase {
 595  public:
 596   typedef R(RunType)(A1, A2, A3, A4, A5);
 597
 598   Callback() : CallbackBase(NULL) { }
 599
 600   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 601   // return the exact Callback<> type.  See base/bind.h for details.
 602   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 603   Callback(internal::BindState<Runnable, BindRunType,
 604            BoundArgsType>* bind_state)
 605       : CallbackBase(bind_state) {
 606
 607     // Force the assignment to a local variable of PolymorphicInvoke
 608     // so the compiler will typecheck that the passed in Run() method has
 609     // the correct type.
 610     PolymorphicInvoke invoke_func =
 611         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 612             ::InvokerType::Run;
 613     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 614   }
 615
 616   bool Equals(const Callback& other) const {
 617     return CallbackBase::Equals(other);
 618   }
 619
 620   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 621         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 622         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 623         typename internal::CallbackParamTraits<A4>::ForwardType a4,
 624         typename internal::CallbackParamTraits<A5>::ForwardType a5) const {
 625     PolymorphicInvoke f =
 626         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 627
 628     return f(bind_state_.get(), internal::CallbackForward(a1),
 629              internal::CallbackForward(a2),
 630              internal::CallbackForward(a3),
 631              internal::CallbackForward(a4),
 632              internal::CallbackForward(a5));
 633   }
 634
 635  private:
 636   typedef R(*PolymorphicInvoke)(
 637       internal::BindStateBase*,
 638           typename internal::CallbackParamTraits<A1>::ForwardType,
 639           typename internal::CallbackParamTraits<A2>::ForwardType,
 640           typename internal::CallbackParamTraits<A3>::ForwardType,
 641           typename internal::CallbackParamTraits<A4>::ForwardType,
 642           typename internal::CallbackParamTraits<A5>::ForwardType);
 643
 644 };
 645
 646 template <typename R, typename A1, typename A2, typename A3, typename A4,
 647     typename A5, typename A6>
 648 class Callback<R(A1, A2, A3, A4, A5, A6)> : public internal::CallbackBase {
 649  public:
 650   typedef R(RunType)(A1, A2, A3, A4, A5, A6);
 651
 652   Callback() : CallbackBase(NULL) { }
 653
 654   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 655   // return the exact Callback<> type.  See base/bind.h for details.
 656   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 657   Callback(internal::BindState<Runnable, BindRunType,
 658            BoundArgsType>* bind_state)
 659       : CallbackBase(bind_state) {
 660
 661     // Force the assignment to a local variable of PolymorphicInvoke
 662     // so the compiler will typecheck that the passed in Run() method has
 663     // the correct type.
 664     PolymorphicInvoke invoke_func =
 665         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 666             ::InvokerType::Run;
 667     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 668   }
 669
 670   bool Equals(const Callback& other) const {
 671     return CallbackBase::Equals(other);
 672   }
 673
 674   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 675         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 676         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 677         typename internal::CallbackParamTraits<A4>::ForwardType a4,
 678         typename internal::CallbackParamTraits<A5>::ForwardType a5,
 679         typename internal::CallbackParamTraits<A6>::ForwardType a6) const {
 680     PolymorphicInvoke f =
 681         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 682
 683     return f(bind_state_.get(), internal::CallbackForward(a1),
 684              internal::CallbackForward(a2),
 685              internal::CallbackForward(a3),
 686              internal::CallbackForward(a4),
 687              internal::CallbackForward(a5),
 688              internal::CallbackForward(a6));
 689   }
 690
 691  private:
 692   typedef R(*PolymorphicInvoke)(
 693       internal::BindStateBase*,
 694           typename internal::CallbackParamTraits<A1>::ForwardType,
 695           typename internal::CallbackParamTraits<A2>::ForwardType,
 696           typename internal::CallbackParamTraits<A3>::ForwardType,
 697           typename internal::CallbackParamTraits<A4>::ForwardType,
 698           typename internal::CallbackParamTraits<A5>::ForwardType,
 699           typename internal::CallbackParamTraits<A6>::ForwardType);
 700
 701 };
 702
 703 template <typename R, typename A1, typename A2, typename A3, typename A4,
 704     typename A5, typename A6, typename A7>
 705 class Callback<R(A1, A2, A3, A4, A5, A6, A7)> : public internal::CallbackBase {
 706  public:
 707   typedef R(RunType)(A1, A2, A3, A4, A5, A6, A7);
 708
 709   Callback() : CallbackBase(NULL) { }
 710
 711   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 712   // return the exact Callback<> type.  See base/bind.h for details.
 713   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 714   Callback(internal::BindState<Runnable, BindRunType,
 715            BoundArgsType>* bind_state)
 716       : CallbackBase(bind_state) {
 717
 718     // Force the assignment to a local variable of PolymorphicInvoke
 719     // so the compiler will typecheck that the passed in Run() method has
 720     // the correct type.
 721     PolymorphicInvoke invoke_func =
 722         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 723             ::InvokerType::Run;
 724     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 725   }
 726
 727   bool Equals(const Callback& other) const {
 728     return CallbackBase::Equals(other);
 729   }
 730
 731   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 732         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 733         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 734         typename internal::CallbackParamTraits<A4>::ForwardType a4,
 735         typename internal::CallbackParamTraits<A5>::ForwardType a5,
 736         typename internal::CallbackParamTraits<A6>::ForwardType a6,
 737         typename internal::CallbackParamTraits<A7>::ForwardType a7) const {
 738     PolymorphicInvoke f =
 739         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 740
 741     return f(bind_state_.get(), internal::CallbackForward(a1),
 742              internal::CallbackForward(a2),
 743              internal::CallbackForward(a3),
 744              internal::CallbackForward(a4),
 745              internal::CallbackForward(a5),
 746              internal::CallbackForward(a6),
 747              internal::CallbackForward(a7));
 748   }
 749
 750  private:
 751   typedef R(*PolymorphicInvoke)(
 752       internal::BindStateBase*,
 753           typename internal::CallbackParamTraits<A1>::ForwardType,
 754           typename internal::CallbackParamTraits<A2>::ForwardType,
 755           typename internal::CallbackParamTraits<A3>::ForwardType,
 756           typename internal::CallbackParamTraits<A4>::ForwardType,
 757           typename internal::CallbackParamTraits<A5>::ForwardType,
 758           typename internal::CallbackParamTraits<A6>::ForwardType,
 759           typename internal::CallbackParamTraits<A7>::ForwardType);
 760
 761 };
 762
 763
 764 // Syntactic sugar to make Callback<void(void)> easier to declare since it
 765 // will be used in a lot of APIs with delayed execution.
 766 typedef Callback<void(void)> Closure;
 767
 768 }  // namespace base
 769
 770 #endif  // BASE_CALLBACK_H