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 issued if the object is destroyed at the time
 147 //   it's issued. 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 //   void foo(int arg) { cout << arg << endl }
 218 //   int n = 1;
 219 //   base::Closure has_ref = base::Bind(&foo, base::ConstRef(n));
 220 //   n = 2;
 221 //   has_ref.Run();  // Prints "2"
 222 //
 223 //   Normally parameters are copied in the closure. DANGER: ConstRef stores a
 224 //   const reference instead, referencing the original parameter. This means
 225 //   that you must ensure the object outlives the callback!
 226 //
 227 //
 228 // -----------------------------------------------------------------------------
 229 // Implementation notes
 230 // -----------------------------------------------------------------------------
 231 //
 232 // WHERE IS THIS DESIGN FROM:
 233 //
 234 // The design Callback and Bind is heavily influenced by C++'s
 235 // tr1::function/tr1::bind, and by the "Google Callback" system used inside
 236 // Google.
 237 //
 238 //
 239 // HOW THE IMPLEMENTATION WORKS:
 240 //
 241 // There are three main components to the system:
 242 //   1) The Callback classes.
 243 //   2) The Bind() functions.
 244 //   3) The arguments wrappers (e.g., Unretained() and ConstRef()).
 245 //
 246 // The Callback classes represent a generic function pointer. Internally,
 247 // it stores a refcounted piece of state that represents the target function
 248 // and all its bound parameters.  Each Callback specialization has a templated
 249 // constructor that takes an BindState<>*.  In the context of the constructor,
 250 // the static type of this BindState<> pointer uniquely identifies the
 251 // function it is representing, all its bound parameters, and a Run() method
 252 // that is capable of invoking the target.
 253 //
 254 // Callback's constructor takes the BindState<>* that has the full static type
 255 // and erases the target function type as well as the types of the bound
 256 // parameters.  It does this by storing a pointer to the specific Run()
 257 // function, and upcasting the state of BindState<>* to a
 258 // BindStateBase*. This is safe as long as this BindStateBase pointer
 259 // is only used with the stored Run() pointer.
 260 //
 261 // To BindState<> objects are created inside the Bind() functions.
 262 // These functions, along with a set of internal templates, are responsible for
 263 //
 264 //  - Unwrapping the function signature into return type, and parameters
 265 //  - Determining the number of parameters that are bound
 266 //  - Creating the BindState storing the bound parameters
 267 //  - Performing compile-time asserts to avoid error-prone behavior
 268 //  - Returning an Callback<> with an arity matching the number of unbound
 269 //    parameters and that knows the correct refcounting semantics for the
 270 //    target object if we are binding a method.
 271 //
 272 // The Bind functions do the above using type-inference, and template
 273 // specializations.
 274 //
 275 // By default Bind() will store copies of all bound parameters, and attempt
 276 // to refcount a target object if the function being bound is a class method.
 277 // These copies are created even if the function takes parameters as const
 278 // references. (Binding to non-const references is forbidden, see bind.h.)
 279 //
 280 // To change this behavior, we introduce a set of argument wrappers
 281 // (e.g., Unretained(), and ConstRef()).  These are simple container templates
 282 // that are passed by value, and wrap a pointer to argument.  See the
 283 // file-level comment in base/bind_helpers.h for more info.
 284 //
 285 // These types are passed to the Unwrap() functions, and the MaybeRefcount()
 286 // functions respectively to modify the behavior of Bind().  The Unwrap()
 287 // and MaybeRefcount() functions change behavior by doing partial
 288 // specialization based on whether or not a parameter is a wrapper type.
 289 //
 290 // ConstRef() is similar to tr1::cref.  Unretained() is specific to Chromium.
 291 //
 292 //
 293 // WHY NOT TR1 FUNCTION/BIND?
 294 //
 295 // Direct use of tr1::function and tr1::bind was considered, but ultimately
 296 // rejected because of the number of copy constructors invocations involved
 297 // in the binding of arguments during construction, and the forwarding of
 298 // arguments during invocation.  These copies will no longer be an issue in
 299 // C++0x because C++0x will support rvalue reference allowing for the compiler
 300 // to avoid these copies.  However, waiting for C++0x is not an option.
 301 //
 302 // Measured with valgrind on gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5), the
 303 // tr1::bind call itself will invoke a non-trivial copy constructor three times
 304 // for each bound parameter.  Also, each when passing a tr1::function, each
 305 // bound argument will be copied again.
 306 //
 307 // In addition to the copies taken at binding and invocation, copying a
 308 // tr1::function causes a copy to be made of all the bound parameters and
 309 // state.
 310 //
 311 // Furthermore, in Chromium, it is desirable for the Callback to take a
 312 // reference on a target object when representing a class method call.  This
 313 // is not supported by tr1.
 314 //
 315 // Lastly, tr1::function and tr1::bind has a more general and flexible API.
 316 // This includes things like argument reordering by use of
 317 // tr1::bind::placeholder, support for non-const reference parameters, and some
 318 // limited amount of subtyping of the tr1::function object (e.g.,
 319 // tr1::function<int(int)> is convertible to tr1::function<void(int)>).
 320 //
 321 // These are not features that are required in Chromium. Some of them, such as
 322 // allowing for reference parameters, and subtyping of functions, may actually
 323 // become a source of errors. Removing support for these features actually
 324 // allows for a simpler implementation, and a terser Currying API.
 325 //
 326 //
 327 // WHY NOT GOOGLE CALLBACKS?
 328 //
 329 // The Google callback system also does not support refcounting.  Furthermore,
 330 // its implementation has a number of strange edge cases with respect to type
 331 // conversion of its arguments.  In particular, the argument's constness must
 332 // at times match exactly the function signature, or the type-inference might
 333 // break.  Given the above, writing a custom solution was easier.
 334 //
 335 //
 336 // MISSING FUNCTIONALITY
 337 //  - Invoking the return of Bind.  Bind(&foo).Run() does not work;
 338 //  - Binding arrays to functions that take a non-const pointer.
 339 //    Example:
 340 //      void Foo(const char* ptr);
 341 //      void Bar(char* ptr);
 342 //      Bind(&Foo, "test");
 343 //      Bind(&Bar, "test");  // This fails because ptr is not const.
 344
 345 namespace base {
 346
 347 // First, we forward declare the Callback class template. This informs the
 348 // compiler that the template only has 1 type parameter which is the function
 349 // signature that the Callback is representing.
 350 //
 351 // After this, create template specializations for 0-7 parameters. Note that
 352 // even though the template typelist grows, the specialization still
 353 // only has one type: the function signature.
 354 //
 355 // If you are thinking of forward declaring Callback in your own header file,
 356 // please include "base/callback_forward.h" instead.
 357 template <typename Sig>
 358 class Callback;
 359
 360 namespace internal {
 361 template <typename Runnable, typename RunType, typename BoundArgsType>
 362 struct BindState;
 363 }  // namespace internal
 364
 365 template <typename R>
 366 class Callback<R(void)> : public internal::CallbackBase {
 367  public:
 368   typedef R(RunType)();
 369
 370   Callback() : CallbackBase(NULL) { }
 371
 372   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 373   // return the exact Callback<> type.  See base/bind.h for details.
 374   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 375   Callback(internal::BindState<Runnable, BindRunType,
 376            BoundArgsType>* bind_state)
 377       : CallbackBase(bind_state) {
 378
 379     // Force the assignment to a local variable of PolymorphicInvoke
 380     // so the compiler will typecheck that the passed in Run() method has
 381     // the correct type.
 382     PolymorphicInvoke invoke_func =
 383         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 384             ::InvokerType::Run;
 385     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 386   }
 387
 388   bool Equals(const Callback& other) const {
 389     return CallbackBase::Equals(other);
 390   }
 391
 392   R Run() const {
 393     PolymorphicInvoke f =
 394         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 395
 396     return f(bind_state_.get());
 397   }
 398
 399  private:
 400   typedef R(*PolymorphicInvoke)(
 401       internal::BindStateBase*);
 402
 403 };
 404
 405 template <typename R, typename A1>
 406 class Callback<R(A1)> : public internal::CallbackBase {
 407  public:
 408   typedef R(RunType)(A1);
 409
 410   Callback() : CallbackBase(NULL) { }
 411
 412   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 413   // return the exact Callback<> type.  See base/bind.h for details.
 414   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 415   Callback(internal::BindState<Runnable, BindRunType,
 416            BoundArgsType>* bind_state)
 417       : CallbackBase(bind_state) {
 418
 419     // Force the assignment to a local variable of PolymorphicInvoke
 420     // so the compiler will typecheck that the passed in Run() method has
 421     // the correct type.
 422     PolymorphicInvoke invoke_func =
 423         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 424             ::InvokerType::Run;
 425     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 426   }
 427
 428   bool Equals(const Callback& other) const {
 429     return CallbackBase::Equals(other);
 430   }
 431
 432   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1) const {
 433     PolymorphicInvoke f =
 434         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 435
 436     return f(bind_state_.get(), internal::CallbackForward(a1));
 437   }
 438
 439  private:
 440   typedef R(*PolymorphicInvoke)(
 441       internal::BindStateBase*,
 442           typename internal::CallbackParamTraits<A1>::ForwardType);
 443
 444 };
 445
 446 template <typename R, typename A1, typename A2>
 447 class Callback<R(A1, A2)> : public internal::CallbackBase {
 448  public:
 449   typedef R(RunType)(A1, A2);
 450
 451   Callback() : CallbackBase(NULL) { }
 452
 453   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 454   // return the exact Callback<> type.  See base/bind.h for details.
 455   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 456   Callback(internal::BindState<Runnable, BindRunType,
 457            BoundArgsType>* bind_state)
 458       : CallbackBase(bind_state) {
 459
 460     // Force the assignment to a local variable of PolymorphicInvoke
 461     // so the compiler will typecheck that the passed in Run() method has
 462     // the correct type.
 463     PolymorphicInvoke invoke_func =
 464         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 465             ::InvokerType::Run;
 466     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 467   }
 468
 469   bool Equals(const Callback& other) const {
 470     return CallbackBase::Equals(other);
 471   }
 472
 473   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 474         typename internal::CallbackParamTraits<A2>::ForwardType a2) const {
 475     PolymorphicInvoke f =
 476         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 477
 478     return f(bind_state_.get(), internal::CallbackForward(a1),
 479              internal::CallbackForward(a2));
 480   }
 481
 482  private:
 483   typedef R(*PolymorphicInvoke)(
 484       internal::BindStateBase*,
 485           typename internal::CallbackParamTraits<A1>::ForwardType,
 486           typename internal::CallbackParamTraits<A2>::ForwardType);
 487
 488 };
 489
 490 template <typename R, typename A1, typename A2, typename A3>
 491 class Callback<R(A1, A2, A3)> : public internal::CallbackBase {
 492  public:
 493   typedef R(RunType)(A1, A2, A3);
 494
 495   Callback() : CallbackBase(NULL) { }
 496
 497   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 498   // return the exact Callback<> type.  See base/bind.h for details.
 499   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 500   Callback(internal::BindState<Runnable, BindRunType,
 501            BoundArgsType>* bind_state)
 502       : CallbackBase(bind_state) {
 503
 504     // Force the assignment to a local variable of PolymorphicInvoke
 505     // so the compiler will typecheck that the passed in Run() method has
 506     // the correct type.
 507     PolymorphicInvoke invoke_func =
 508         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 509             ::InvokerType::Run;
 510     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 511   }
 512
 513   bool Equals(const Callback& other) const {
 514     return CallbackBase::Equals(other);
 515   }
 516
 517   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 518         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 519         typename internal::CallbackParamTraits<A3>::ForwardType a3) const {
 520     PolymorphicInvoke f =
 521         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 522
 523     return f(bind_state_.get(), internal::CallbackForward(a1),
 524              internal::CallbackForward(a2),
 525              internal::CallbackForward(a3));
 526   }
 527
 528  private:
 529   typedef R(*PolymorphicInvoke)(
 530       internal::BindStateBase*,
 531           typename internal::CallbackParamTraits<A1>::ForwardType,
 532           typename internal::CallbackParamTraits<A2>::ForwardType,
 533           typename internal::CallbackParamTraits<A3>::ForwardType);
 534
 535 };
 536
 537 template <typename R, typename A1, typename A2, typename A3, typename A4>
 538 class Callback<R(A1, A2, A3, A4)> : public internal::CallbackBase {
 539  public:
 540   typedef R(RunType)(A1, A2, A3, A4);
 541
 542   Callback() : CallbackBase(NULL) { }
 543
 544   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 545   // return the exact Callback<> type.  See base/bind.h for details.
 546   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 547   Callback(internal::BindState<Runnable, BindRunType,
 548            BoundArgsType>* bind_state)
 549       : CallbackBase(bind_state) {
 550
 551     // Force the assignment to a local variable of PolymorphicInvoke
 552     // so the compiler will typecheck that the passed in Run() method has
 553     // the correct type.
 554     PolymorphicInvoke invoke_func =
 555         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 556             ::InvokerType::Run;
 557     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 558   }
 559
 560   bool Equals(const Callback& other) const {
 561     return CallbackBase::Equals(other);
 562   }
 563
 564   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 565         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 566         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 567         typename internal::CallbackParamTraits<A4>::ForwardType a4) const {
 568     PolymorphicInvoke f =
 569         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 570
 571     return f(bind_state_.get(), internal::CallbackForward(a1),
 572              internal::CallbackForward(a2),
 573              internal::CallbackForward(a3),
 574              internal::CallbackForward(a4));
 575   }
 576
 577  private:
 578   typedef R(*PolymorphicInvoke)(
 579       internal::BindStateBase*,
 580           typename internal::CallbackParamTraits<A1>::ForwardType,
 581           typename internal::CallbackParamTraits<A2>::ForwardType,
 582           typename internal::CallbackParamTraits<A3>::ForwardType,
 583           typename internal::CallbackParamTraits<A4>::ForwardType);
 584
 585 };
 586
 587 template <typename R, typename A1, typename A2, typename A3, typename A4,
 588     typename A5>
 589 class Callback<R(A1, A2, A3, A4, A5)> : public internal::CallbackBase {
 590  public:
 591   typedef R(RunType)(A1, A2, A3, A4, A5);
 592
 593   Callback() : CallbackBase(NULL) { }
 594
 595   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 596   // return the exact Callback<> type.  See base/bind.h for details.
 597   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 598   Callback(internal::BindState<Runnable, BindRunType,
 599            BoundArgsType>* bind_state)
 600       : CallbackBase(bind_state) {
 601
 602     // Force the assignment to a local variable of PolymorphicInvoke
 603     // so the compiler will typecheck that the passed in Run() method has
 604     // the correct type.
 605     PolymorphicInvoke invoke_func =
 606         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 607             ::InvokerType::Run;
 608     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 609   }
 610
 611   bool Equals(const Callback& other) const {
 612     return CallbackBase::Equals(other);
 613   }
 614
 615   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 616         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 617         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 618         typename internal::CallbackParamTraits<A4>::ForwardType a4,
 619         typename internal::CallbackParamTraits<A5>::ForwardType a5) const {
 620     PolymorphicInvoke f =
 621         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 622
 623     return f(bind_state_.get(), internal::CallbackForward(a1),
 624              internal::CallbackForward(a2),
 625              internal::CallbackForward(a3),
 626              internal::CallbackForward(a4),
 627              internal::CallbackForward(a5));
 628   }
 629
 630  private:
 631   typedef R(*PolymorphicInvoke)(
 632       internal::BindStateBase*,
 633           typename internal::CallbackParamTraits<A1>::ForwardType,
 634           typename internal::CallbackParamTraits<A2>::ForwardType,
 635           typename internal::CallbackParamTraits<A3>::ForwardType,
 636           typename internal::CallbackParamTraits<A4>::ForwardType,
 637           typename internal::CallbackParamTraits<A5>::ForwardType);
 638
 639 };
 640
 641 template <typename R, typename A1, typename A2, typename A3, typename A4,
 642     typename A5, typename A6>
 643 class Callback<R(A1, A2, A3, A4, A5, A6)> : public internal::CallbackBase {
 644  public:
 645   typedef R(RunType)(A1, A2, A3, A4, A5, A6);
 646
 647   Callback() : CallbackBase(NULL) { }
 648
 649   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 650   // return the exact Callback<> type.  See base/bind.h for details.
 651   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 652   Callback(internal::BindState<Runnable, BindRunType,
 653            BoundArgsType>* bind_state)
 654       : CallbackBase(bind_state) {
 655
 656     // Force the assignment to a local variable of PolymorphicInvoke
 657     // so the compiler will typecheck that the passed in Run() method has
 658     // the correct type.
 659     PolymorphicInvoke invoke_func =
 660         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 661             ::InvokerType::Run;
 662     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 663   }
 664
 665   bool Equals(const Callback& other) const {
 666     return CallbackBase::Equals(other);
 667   }
 668
 669   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 670         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 671         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 672         typename internal::CallbackParamTraits<A4>::ForwardType a4,
 673         typename internal::CallbackParamTraits<A5>::ForwardType a5,
 674         typename internal::CallbackParamTraits<A6>::ForwardType a6) const {
 675     PolymorphicInvoke f =
 676         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 677
 678     return f(bind_state_.get(), internal::CallbackForward(a1),
 679              internal::CallbackForward(a2),
 680              internal::CallbackForward(a3),
 681              internal::CallbackForward(a4),
 682              internal::CallbackForward(a5),
 683              internal::CallbackForward(a6));
 684   }
 685
 686  private:
 687   typedef R(*PolymorphicInvoke)(
 688       internal::BindStateBase*,
 689           typename internal::CallbackParamTraits<A1>::ForwardType,
 690           typename internal::CallbackParamTraits<A2>::ForwardType,
 691           typename internal::CallbackParamTraits<A3>::ForwardType,
 692           typename internal::CallbackParamTraits<A4>::ForwardType,
 693           typename internal::CallbackParamTraits<A5>::ForwardType,
 694           typename internal::CallbackParamTraits<A6>::ForwardType);
 695
 696 };
 697
 698 template <typename R, typename A1, typename A2, typename A3, typename A4,
 699     typename A5, typename A6, typename A7>
 700 class Callback<R(A1, A2, A3, A4, A5, A6, A7)> : public internal::CallbackBase {
 701  public:
 702   typedef R(RunType)(A1, A2, A3, A4, A5, A6, A7);
 703
 704   Callback() : CallbackBase(NULL) { }
 705
 706   // Note that this constructor CANNOT be explicit, and that Bind() CANNOT
 707   // return the exact Callback<> type.  See base/bind.h for details.
 708   template <typename Runnable, typename BindRunType, typename BoundArgsType>
 709   Callback(internal::BindState<Runnable, BindRunType,
 710            BoundArgsType>* bind_state)
 711       : CallbackBase(bind_state) {
 712
 713     // Force the assignment to a local variable of PolymorphicInvoke
 714     // so the compiler will typecheck that the passed in Run() method has
 715     // the correct type.
 716     PolymorphicInvoke invoke_func =
 717         &internal::BindState<Runnable, BindRunType, BoundArgsType>
 718             ::InvokerType::Run;
 719     polymorphic_invoke_ = reinterpret_cast<InvokeFuncStorage>(invoke_func);
 720   }
 721
 722   bool Equals(const Callback& other) const {
 723     return CallbackBase::Equals(other);
 724   }
 725
 726   R Run(typename internal::CallbackParamTraits<A1>::ForwardType a1,
 727         typename internal::CallbackParamTraits<A2>::ForwardType a2,
 728         typename internal::CallbackParamTraits<A3>::ForwardType a3,
 729         typename internal::CallbackParamTraits<A4>::ForwardType a4,
 730         typename internal::CallbackParamTraits<A5>::ForwardType a5,
 731         typename internal::CallbackParamTraits<A6>::ForwardType a6,
 732         typename internal::CallbackParamTraits<A7>::ForwardType a7) const {
 733     PolymorphicInvoke f =
 734         reinterpret_cast<PolymorphicInvoke>(polymorphic_invoke_);
 735
 736     return f(bind_state_.get(), internal::CallbackForward(a1),
 737              internal::CallbackForward(a2),
 738              internal::CallbackForward(a3),
 739              internal::CallbackForward(a4),
 740              internal::CallbackForward(a5),
 741              internal::CallbackForward(a6),
 742              internal::CallbackForward(a7));
 743   }
 744
 745  private:
 746   typedef R(*PolymorphicInvoke)(
 747       internal::BindStateBase*,
 748           typename internal::CallbackParamTraits<A1>::ForwardType,
 749           typename internal::CallbackParamTraits<A2>::ForwardType,
 750           typename internal::CallbackParamTraits<A3>::ForwardType,
 751           typename internal::CallbackParamTraits<A4>::ForwardType,
 752           typename internal::CallbackParamTraits<A5>::ForwardType,
 753           typename internal::CallbackParamTraits<A6>::ForwardType,
 754           typename internal::CallbackParamTraits<A7>::ForwardType);
 755
 756 };
 757
 758
 759 // Syntactic sugar to make Callbacks<void(void)> easier to declare since it
 760 // will be used in a lot of APIs with delayed execution.
 761 typedef Callback<void(void)> Closure;
 762
 763 }  // namespace base
 764
 765 #endif  // BASE_CALLBACK_H