libstdc++

future

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00001 // <future> -*- C++ -*-
00002 
00003 // Copyright (C) 2009, 2010, 2011 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file include/future
00026  *  This is a Standard C++ Library header.
00027  */
00028 
00029 #ifndef _GLIBCXX_FUTURE
00030 #define _GLIBCXX_FUTURE 1
00031 
00032 #pragma GCC system_header
00033 
00034 #ifndef __GXX_EXPERIMENTAL_CXX0X__
00035 # include <bits/c++0x_warning.h>
00036 #else
00037 
00038 #include <functional>
00039 #include <memory>
00040 #include <mutex>
00041 #include <thread>
00042 #include <condition_variable>
00043 #include <system_error>
00044 #include <exception>
00045 #include <atomic>
00046 #include <bits/functexcept.h>
00047 
00048 namespace std _GLIBCXX_VISIBILITY(default)
00049 {
00050 _GLIBCXX_BEGIN_NAMESPACE_VERSION
00051 
00052   /**
00053    * @defgroup futures Futures
00054    * @ingroup concurrency
00055    *
00056    * Classes for futures support.
00057    * @{
00058    */
00059 
00060   /// Error code for futures
00061   enum class future_errc
00062   {
00063     broken_promise,
00064     future_already_retrieved,
00065     promise_already_satisfied,
00066     no_state
00067   };
00068 
00069   /// Specialization.
00070   template<>
00071     struct is_error_code_enum<future_errc> : public true_type { };
00072 
00073   /// Points to a statically-allocated object derived from error_category.
00074   const error_category&
00075   future_category();
00076 
00077   /// Overload for make_error_code.
00078   inline error_code 
00079   make_error_code(future_errc __errc)
00080   { return error_code(static_cast<int>(__errc), future_category()); }
00081 
00082   /// Overload for make_error_condition.
00083   inline error_condition 
00084   make_error_condition(future_errc __errc)
00085   { return error_condition(static_cast<int>(__errc), future_category()); }
00086 
00087   /**
00088    *  @brief Exception type thrown by futures.
00089    *  @ingroup exceptions
00090    */
00091   class future_error : public logic_error
00092   {
00093     error_code          _M_code;
00094 
00095   public:
00096     explicit future_error(error_code __ec)
00097     : logic_error("std::future_error"), _M_code(__ec)
00098     { }
00099 
00100     virtual ~future_error() throw();
00101 
00102     virtual const char* 
00103     what() const throw();
00104 
00105     const error_code& 
00106     code() const throw() { return _M_code; }
00107   };
00108 
00109   // Forward declarations.
00110   template<typename _Res>
00111     class future;
00112 
00113   template<typename _Res>
00114     class shared_future;
00115 
00116   template<typename _Res>
00117     class atomic_future;
00118 
00119   template<typename _Signature> 
00120     class packaged_task;
00121 
00122   template<typename _Res>
00123     class promise;
00124 
00125   /// Launch code for futures
00126   enum class launch 
00127   { 
00128     any, 
00129     async, 
00130     sync 
00131   };
00132 
00133   /// Status code for futures
00134   enum class future_status 
00135   {
00136     ready,
00137     timeout,
00138     deferred
00139   };
00140 
00141   template<typename _Fn, typename... _Args>
00142     future<typename result_of<_Fn(_Args...)>::type>
00143     async(launch __policy, _Fn&& __fn, _Args&&... __args);
00144 
00145   template<typename _Fn, typename... _Args>
00146     typename
00147     enable_if<!is_same<typename decay<_Fn>::type, launch>::value,
00148               future<decltype(std::declval<_Fn>()(std::declval<_Args>()...))>
00149              >::type
00150     async(_Fn&& __fn, _Args&&... __args);
00151 
00152 #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) \
00153   && defined(_GLIBCXX_ATOMIC_BUILTINS_4)
00154 
00155   /// Base class and enclosing scope.
00156   struct __future_base
00157   {
00158     /// Base class for results.
00159     struct _Result_base
00160     {
00161       exception_ptr     _M_error;
00162 
00163       _Result_base(const _Result_base&) = delete;
00164       _Result_base& operator=(const _Result_base&) = delete;
00165 
00166       // _M_destroy() allows derived classes to control deallocation
00167       virtual void _M_destroy() = 0;
00168 
00169       struct _Deleter
00170       {
00171     void operator()(_Result_base* __fr) const { __fr->_M_destroy(); }
00172       };
00173 
00174     protected:
00175       _Result_base();
00176       virtual ~_Result_base();
00177     };
00178 
00179     /// Result.
00180     template<typename _Res>
00181       struct _Result : _Result_base
00182       {
00183       private:
00184     typedef alignment_of<_Res>              __a_of;
00185     typedef aligned_storage<sizeof(_Res), __a_of::value>    __align_storage;
00186     typedef typename __align_storage::type          __align_type;
00187 
00188     __align_type        _M_storage;
00189     bool            _M_initialized;
00190 
00191       public:
00192     _Result() : _M_initialized() { }
00193     
00194     ~_Result()
00195     {
00196       if (_M_initialized)
00197         _M_value().~_Res();
00198     }
00199 
00200     // Return lvalue, future will add const or rvalue-reference
00201     _Res& 
00202     _M_value() { return *static_cast<_Res*>(_M_addr()); }
00203 
00204     void
00205     _M_set(const _Res& __res)
00206     {
00207       ::new (_M_addr()) _Res(__res);
00208       _M_initialized = true;
00209     }
00210 
00211     void
00212     _M_set(_Res&& __res)
00213     {
00214       ::new (_M_addr()) _Res(std::move(__res));
00215       _M_initialized = true;
00216     }
00217 
00218       private:
00219     void _M_destroy() { delete this; }
00220 
00221     void* _M_addr() { return static_cast<void*>(&_M_storage); }
00222     };
00223 
00224     // TODO: use template alias when available
00225     /*
00226       template<typename _Res>
00227       using _Ptr = unique_ptr<_Res, _Result_base::_Deleter>;
00228     */
00229     /// A unique_ptr based on the instantiating type.
00230     template<typename _Res>
00231       struct _Ptr
00232       {
00233     typedef unique_ptr<_Res, _Result_base::_Deleter> type;
00234       };
00235 
00236     /// Result_alloc.
00237     template<typename _Res, typename _Alloc>
00238       struct _Result_alloc : _Result<_Res>, _Alloc
00239       {
00240         typedef typename _Alloc::template rebind<_Result_alloc>::other
00241           __allocator_type;
00242 
00243         explicit
00244     _Result_alloc(const _Alloc& __a) : _Result<_Res>(), _Alloc(__a)
00245         { }
00246     
00247       private:
00248     void _M_destroy()
00249         {
00250           __allocator_type __a(*this);
00251           __a.destroy(this);
00252           __a.deallocate(this, 1);
00253         }
00254       };
00255 
00256     template<typename _Res, typename _Allocator>
00257       static typename _Ptr<_Result_alloc<_Res, _Allocator>>::type
00258       _S_allocate_result(const _Allocator& __a)
00259       {
00260         typedef _Result_alloc<_Res, _Allocator> __result_type;
00261         typename __result_type::__allocator_type __a2(__a);
00262         __result_type* __p = __a2.allocate(1);
00263         __try
00264     {
00265           __a2.construct(__p, __a);
00266         }
00267         __catch(...)
00268         {
00269           __a2.deallocate(__p, 1);
00270           __throw_exception_again;
00271         }
00272         return typename _Ptr<__result_type>::type(__p);
00273       }
00274 
00275 
00276     /// Base class for state between a promise and one or more
00277     /// associated futures.
00278     class _State_base
00279     {
00280       typedef _Ptr<_Result_base>::type _Ptr_type;
00281 
00282       _Ptr_type         _M_result;
00283       mutex                 _M_mutex;
00284       condition_variable    _M_cond;
00285       atomic_flag           _M_retrieved;
00286       once_flag         _M_once;
00287 
00288     public:
00289       _State_base() : _M_result(), _M_retrieved(ATOMIC_FLAG_INIT) { }
00290       _State_base(const _State_base&) = delete;
00291       _State_base& operator=(const _State_base&) = delete;
00292       virtual ~_State_base();
00293 
00294       _Result_base&
00295       wait()
00296       {
00297     _M_run_deferred();
00298     unique_lock<mutex> __lock(_M_mutex);
00299     if (!_M_ready())
00300       _M_cond.wait(__lock, std::bind<bool>(&_State_base::_M_ready, this));
00301     return *_M_result;
00302       }
00303 
00304       template<typename _Rep, typename _Period>
00305         bool
00306         wait_for(const chrono::duration<_Rep, _Period>& __rel)
00307         {
00308       unique_lock<mutex> __lock(_M_mutex);
00309       auto __bound = std::bind<bool>(&_State_base::_M_ready, this);
00310       return _M_ready() || _M_cond.wait_for(__lock, __rel, __bound);
00311     }
00312 
00313       template<typename _Clock, typename _Duration>
00314         bool
00315         wait_until(const chrono::time_point<_Clock, _Duration>& __abs)
00316         {
00317       unique_lock<mutex> __lock(_M_mutex);
00318       auto __bound = std::bind<bool>(&_State_base::_M_ready, this);
00319       return _M_ready() || _M_cond.wait_until(__lock, __abs, __bound);
00320     }
00321 
00322       void
00323       _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false)
00324       {
00325         bool __set = __ignore_failure;
00326         // all calls to this function are serialized,
00327         // side-effects of invoking __res only happen once
00328         call_once(_M_once, &_State_base::_M_do_set, this, ref(__res),
00329             ref(__set));
00330         if (!__set)
00331           __throw_future_error(int(future_errc::promise_already_satisfied));
00332       }
00333 
00334       void
00335       _M_break_promise(_Ptr_type __res)
00336       {
00337     if (static_cast<bool>(__res))
00338       {
00339         error_code __ec(make_error_code(future_errc::broken_promise));
00340         __res->_M_error = copy_exception(future_error(__ec));
00341         {
00342           lock_guard<mutex> __lock(_M_mutex);
00343           _M_result.swap(__res);
00344         }
00345         _M_cond.notify_all();
00346       }
00347       }
00348 
00349       // Called when this object is passed to a future.
00350       void
00351       _M_set_retrieved_flag()
00352       {
00353     if (_M_retrieved.test_and_set())
00354       __throw_future_error(int(future_errc::future_already_retrieved));
00355       }
00356 
00357       template<typename _Res, typename _Arg>
00358         struct _Setter;
00359 
00360       // set lvalues
00361       template<typename _Res, typename _Arg>
00362         struct _Setter<_Res, _Arg&>
00363         {
00364           // check this is only used by promise<R>::set_value(const R&)
00365           // or promise<R>::set_value(R&)
00366           static_assert(is_same<_Res, _Arg&>::value  // promise<R&>
00367               || is_same<const _Res, _Arg>::value,  // promise<R>
00368               "Invalid specialisation");
00369 
00370           typename promise<_Res>::_Ptr_type operator()()
00371           {
00372             _State_base::_S_check(_M_promise->_M_future);
00373             _M_promise->_M_storage->_M_set(_M_arg);
00374             return std::move(_M_promise->_M_storage);
00375           }
00376           promise<_Res>*    _M_promise;
00377           _Arg&             _M_arg;
00378         };
00379 
00380       // set rvalues
00381       template<typename _Res>
00382         struct _Setter<_Res, _Res&&>
00383         {
00384           typename promise<_Res>::_Ptr_type operator()()
00385           {
00386             _State_base::_S_check(_M_promise->_M_future);
00387             _M_promise->_M_storage->_M_set(std::move(_M_arg));
00388             return std::move(_M_promise->_M_storage);
00389           }
00390           promise<_Res>*    _M_promise;
00391           _Res&             _M_arg;
00392         };
00393 
00394       struct __exception_ptr_tag { };
00395 
00396       // set exceptions
00397       template<typename _Res>
00398         struct _Setter<_Res, __exception_ptr_tag>
00399         {
00400           typename promise<_Res>::_Ptr_type operator()()
00401           {
00402             _State_base::_S_check(_M_promise->_M_future);
00403             _M_promise->_M_storage->_M_error = _M_ex;
00404             return std::move(_M_promise->_M_storage);
00405           }
00406 
00407           promise<_Res>*   _M_promise;
00408           exception_ptr&    _M_ex;
00409         };
00410 
00411       template<typename _Res, typename _Arg>
00412         static _Setter<_Res, _Arg&&>
00413         __setter(promise<_Res>* __prom, _Arg&& __arg)
00414         {
00415           return _Setter<_Res, _Arg&&>{ __prom, __arg };
00416         }
00417 
00418       template<typename _Res>
00419         static _Setter<_Res, __exception_ptr_tag>
00420         __setter(exception_ptr& __ex, promise<_Res>* __prom)
00421         {
00422           return _Setter<_Res, __exception_ptr_tag>{ __prom, __ex };
00423         }
00424 
00425       static _Setter<void, void>
00426       __setter(promise<void>* __prom);
00427 
00428       template<typename _Tp>
00429         static bool
00430         _S_check(const shared_ptr<_Tp>& __p)
00431         {
00432           if (!static_cast<bool>(__p))
00433             __throw_future_error((int)future_errc::no_state);
00434         }
00435 
00436     private:
00437       void
00438       _M_do_set(function<_Ptr_type()>& __f, bool& __set)
00439       {
00440         _Ptr_type __res = __f();
00441         {
00442           lock_guard<mutex> __lock(_M_mutex);
00443           _M_result.swap(__res);
00444         }
00445         _M_cond.notify_all();
00446         __set = true;
00447       }
00448 
00449       bool _M_ready() const { return static_cast<bool>(_M_result); }
00450 
00451       virtual void _M_run_deferred() { }
00452     };
00453 
00454     template<typename _Res>
00455       class _Deferred_state;
00456 
00457     template<typename _Res>
00458       class _Async_state;
00459 
00460     template<typename _Signature>
00461       class _Task_state;
00462 
00463     template<typename _StateT, typename _Res = typename _StateT::_Res_type>
00464       struct _Task_setter;
00465   };
00466 
00467   /// Partial specialization for reference types.
00468   template<typename _Res>
00469     struct __future_base::_Result<_Res&> : __future_base::_Result_base
00470     {
00471       _Result() : _M_value_ptr() { }
00472 
00473       void _M_set(_Res& __res) { _M_value_ptr = &__res; }
00474 
00475       _Res& _M_get() { return *_M_value_ptr; }
00476 
00477     private:
00478       _Res*             _M_value_ptr;
00479       
00480       void _M_destroy() { delete this; }
00481     };
00482 
00483   /// Explicit specialization for void.
00484   template<>
00485     struct __future_base::_Result<void> : __future_base::_Result_base
00486     {
00487     private:
00488       void _M_destroy() { delete this; }
00489     };
00490 
00491 
00492   /// Common implementation for future and shared_future.
00493   template<typename _Res>
00494     class __basic_future : public __future_base
00495     {
00496     protected:
00497       typedef shared_ptr<_State_base>       __state_type;
00498       typedef __future_base::_Result<_Res>& __result_type;
00499 
00500     private:
00501       __state_type      _M_state;
00502 
00503     public:
00504       // Disable copying.
00505       __basic_future(const __basic_future&) = delete;
00506       __basic_future& operator=(const __basic_future&) = delete;
00507 
00508       bool 
00509       valid() const { return static_cast<bool>(_M_state); }
00510 
00511       void 
00512       wait() const
00513       {
00514         _State_base::_S_check(_M_state);
00515         _M_state->wait();
00516       }
00517 
00518       template<typename _Rep, typename _Period>
00519         bool
00520         wait_for(const chrono::duration<_Rep, _Period>& __rel) const
00521         {
00522           _State_base::_S_check(_M_state);
00523           return _M_state->wait_for(__rel);
00524         }
00525 
00526       template<typename _Clock, typename _Duration>
00527         bool
00528         wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const
00529         {
00530           _State_base::_S_check(_M_state);
00531           return _M_state->wait_until(__abs);
00532         }
00533 
00534     protected:
00535       /// Wait for the state to be ready and rethrow any stored exception
00536       __result_type
00537       _M_get_result()
00538       {
00539         _State_base::_S_check(_M_state);
00540         _Result_base& __res = _M_state->wait();
00541         if (!(__res._M_error == 0))
00542           rethrow_exception(__res._M_error);
00543         return static_cast<__result_type>(__res);
00544       }
00545 
00546       void _M_swap(__basic_future& __that)
00547       {
00548         _M_state.swap(__that._M_state);
00549       }
00550 
00551       // Construction of a future by promise::get_future()
00552       explicit
00553       __basic_future(const __state_type& __state) : _M_state(__state)
00554       {
00555         _State_base::_S_check(_M_state);
00556         _M_state->_M_set_retrieved_flag();
00557       }
00558 
00559       // Copy construction from a shared_future
00560       explicit
00561       __basic_future(const shared_future<_Res>&);
00562 
00563       // Move construction from a shared_future
00564       explicit
00565       __basic_future(shared_future<_Res>&&);
00566 
00567       // Move construction from a future
00568       explicit
00569       __basic_future(future<_Res>&&);
00570 
00571       constexpr __basic_future() : _M_state() { }
00572 
00573       struct _Reset
00574       {
00575         explicit _Reset(__basic_future& __fut) : _M_fut(__fut) { }
00576         ~_Reset() { _M_fut._M_state.reset(); }
00577         __basic_future& _M_fut;
00578       };
00579     };
00580 
00581 
00582   /// Primary template for future.
00583   template<typename _Res>
00584     class future : public __basic_future<_Res>
00585     {
00586       friend class promise<_Res>;
00587       template<typename> friend class packaged_task;
00588       template<typename _Fn, typename... _Args>
00589         friend future<typename result_of<_Fn(_Args...)>::type>
00590         async(launch, _Fn&&, _Args&&...);
00591 
00592       typedef __basic_future<_Res> _Base_type;
00593       typedef typename _Base_type::__state_type __state_type;
00594 
00595       explicit
00596       future(const __state_type& __state) : _Base_type(__state) { }
00597 
00598     public:
00599       constexpr future() : _Base_type() { }
00600 
00601       /// Move constructor
00602       future(future&& __uf) : _Base_type(std::move(__uf)) { }
00603 
00604       // Disable copying
00605       future(const future&) = delete;
00606       future& operator=(const future&) = delete;
00607 
00608       future& operator=(future&& __fut)
00609       {
00610         future(std::move(__fut))._M_swap(*this);
00611         return *this;
00612       }
00613 
00614       /// Retrieving the value
00615       _Res
00616       get()
00617       {
00618         typename _Base_type::_Reset __reset(*this);
00619         return std::move(this->_M_get_result()._M_value());
00620       }
00621     };
00622  
00623   /// Partial specialization for future<R&>
00624   template<typename _Res>
00625     class future<_Res&> : public __basic_future<_Res&>
00626     {
00627       friend class promise<_Res&>;
00628       template<typename> friend class packaged_task;
00629       template<typename _Fn, typename... _Args>
00630         friend future<typename result_of<_Fn(_Args...)>::type>
00631         async(launch, _Fn&&, _Args&&...);
00632 
00633       typedef __basic_future<_Res&> _Base_type;
00634       typedef typename _Base_type::__state_type __state_type;
00635 
00636       explicit
00637       future(const __state_type& __state) : _Base_type(__state) { }
00638 
00639     public:
00640       constexpr future() : _Base_type() { }
00641 
00642       /// Move constructor
00643       future(future&& __uf) : _Base_type(std::move(__uf)) { }
00644 
00645       // Disable copying
00646       future(const future&) = delete;
00647       future& operator=(const future&) = delete;
00648 
00649       future& operator=(future&& __fut)
00650       {
00651         future(std::move(__fut))._M_swap(*this);
00652         return *this;
00653       }
00654 
00655       /// Retrieving the value
00656       _Res& 
00657       get()
00658       {
00659         typename _Base_type::_Reset __reset(*this);
00660         return this->_M_get_result()._M_get();
00661       }
00662     };
00663 
00664   /// Explicit specialization for future<void>
00665   template<>
00666     class future<void> : public __basic_future<void>
00667     {
00668       friend class promise<void>;
00669       template<typename> friend class packaged_task;
00670       template<typename _Fn, typename... _Args>
00671         friend future<typename result_of<_Fn(_Args...)>::type>
00672         async(launch, _Fn&&, _Args&&...);
00673 
00674       typedef __basic_future<void> _Base_type;
00675       typedef typename _Base_type::__state_type __state_type;
00676 
00677       explicit
00678       future(const __state_type& __state) : _Base_type(__state) { }
00679 
00680     public:
00681       constexpr future() : _Base_type() { }
00682 
00683       /// Move constructor
00684       future(future&& __uf) : _Base_type(std::move(__uf)) { }
00685 
00686       // Disable copying
00687       future(const future&) = delete;
00688       future& operator=(const future&) = delete;
00689 
00690       future& operator=(future&& __fut)
00691       {
00692         future(std::move(__fut))._M_swap(*this);
00693         return *this;
00694       }
00695 
00696       /// Retrieving the value
00697       void 
00698       get()
00699       {
00700         typename _Base_type::_Reset __reset(*this);
00701         this->_M_get_result();
00702       }
00703     };
00704 
00705 
00706   /// Primary template for shared_future.
00707   template<typename _Res>
00708     class shared_future : public __basic_future<_Res>
00709     {
00710       typedef __basic_future<_Res> _Base_type;
00711 
00712     public:
00713       constexpr shared_future() : _Base_type() { }
00714 
00715       /// Copy constructor
00716       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
00717 
00718       /// Construct from a future rvalue
00719       shared_future(future<_Res>&& __uf)
00720       : _Base_type(std::move(__uf))
00721       { }
00722 
00723       /// Construct from a shared_future rvalue
00724       shared_future(shared_future&& __sf)
00725       : _Base_type(std::move(__sf))
00726       { }
00727 
00728       shared_future& operator=(const shared_future& __sf)
00729       {
00730         shared_future(__sf)._M_swap(*this);
00731         return *this;
00732       }
00733 
00734       shared_future& operator=(shared_future&& __sf)
00735       {
00736         shared_future(std::move(__sf))._M_swap(*this);
00737         return *this;
00738       }
00739 
00740       /// Retrieving the value
00741       const _Res&
00742       get()
00743       {
00744     typename _Base_type::__result_type __r = this->_M_get_result();
00745     _Res& __rs(__r._M_value());
00746     return __rs;
00747       }
00748     };
00749  
00750   /// Partial specialization for shared_future<R&>
00751   template<typename _Res>
00752     class shared_future<_Res&> : public __basic_future<_Res&>
00753     {
00754       typedef __basic_future<_Res&>           _Base_type;
00755 
00756     public:
00757       constexpr shared_future() : _Base_type() { }
00758 
00759       /// Copy constructor
00760       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
00761 
00762       /// Construct from a future rvalue
00763       shared_future(future<_Res&>&& __uf)
00764       : _Base_type(std::move(__uf))
00765       { }
00766 
00767       /// Construct from a shared_future rvalue
00768       shared_future(shared_future&& __sf)
00769       : _Base_type(std::move(__sf))
00770       { }
00771 
00772       shared_future& operator=(const shared_future& __sf)
00773       {
00774         shared_future(__sf)._M_swap(*this);
00775         return *this;
00776       }
00777 
00778       shared_future& operator=(shared_future&& __sf)
00779       {
00780         shared_future(std::move(__sf))._M_swap(*this);
00781         return *this;
00782       }
00783 
00784       /// Retrieving the value
00785       _Res& 
00786       get() { return this->_M_get_result()._M_get(); }
00787     };
00788 
00789   /// Explicit specialization for shared_future<void>
00790   template<>
00791     class shared_future<void> : public __basic_future<void>
00792     {
00793       typedef __basic_future<void> _Base_type;
00794 
00795     public:
00796       constexpr shared_future() : _Base_type() { }
00797 
00798       /// Copy constructor
00799       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
00800 
00801       /// Construct from a future rvalue
00802       shared_future(future<void>&& __uf)
00803       : _Base_type(std::move(__uf))
00804       { }
00805 
00806       /// Construct from a shared_future rvalue
00807       shared_future(shared_future&& __sf)
00808       : _Base_type(std::move(__sf))
00809       { }
00810 
00811       shared_future& operator=(const shared_future& __sf)
00812       {
00813         shared_future(__sf)._M_swap(*this);
00814         return *this;
00815       }
00816 
00817       shared_future& operator=(shared_future&& __sf)
00818       {
00819         shared_future(std::move(__sf))._M_swap(*this);
00820         return *this;
00821       }
00822 
00823       // Retrieving the value
00824       void 
00825       get() { this->_M_get_result(); }
00826     };
00827 
00828   // Now we can define the protected __basic_future constructors.
00829   template<typename _Res>
00830     inline __basic_future<_Res>::
00831     __basic_future(const shared_future<_Res>& __sf)
00832     : _M_state(__sf._M_state)
00833     { }
00834 
00835   template<typename _Res>
00836     inline __basic_future<_Res>::
00837     __basic_future(shared_future<_Res>&& __sf)
00838     : _M_state(std::move(__sf._M_state))
00839     { }
00840 
00841   template<typename _Res>
00842     inline __basic_future<_Res>::
00843     __basic_future(future<_Res>&& __uf)
00844     : _M_state(std::move(__uf._M_state))
00845     { }
00846 
00847 
00848   /// Primary template for promise
00849   template<typename _Res>
00850     class promise
00851     {
00852       typedef __future_base::_State_base            _State;
00853       typedef __future_base::_Result<_Res>          _Res_type;
00854       typedef typename __future_base::_Ptr<_Res_type>::type _Ptr_type;
00855       template<typename, typename> friend class _State::_Setter;
00856       
00857       shared_ptr<_State>                        _M_future;
00858       _Ptr_type                                 _M_storage;
00859 
00860     public:
00861       promise()
00862       : _M_future(std::make_shared<_State>()),
00863     _M_storage(new _Res_type())
00864       { }
00865 
00866       promise(promise&& __rhs)
00867       : _M_future(std::move(__rhs._M_future)),
00868     _M_storage(std::move(__rhs._M_storage))
00869       { }
00870 
00871       template<typename _Allocator>
00872         promise(allocator_arg_t, const _Allocator& __a)
00873         : _M_future(std::allocate_shared<_State>(__a)),
00874       _M_storage(__future_base::_S_allocate_result<_Res>(__a))
00875         { }
00876 
00877       promise(const promise&) = delete;
00878 
00879       ~promise()
00880       {
00881         if (static_cast<bool>(_M_future) && !_M_future.unique())
00882           _M_future->_M_break_promise(std::move(_M_storage));
00883       }
00884 
00885       // Assignment
00886       promise&
00887       operator=(promise&& __rhs)
00888       {
00889         promise(std::move(__rhs)).swap(*this);
00890         return *this;
00891       }
00892 
00893       promise& operator=(const promise&) = delete;
00894 
00895       void
00896       swap(promise& __rhs)
00897       {
00898         _M_future.swap(__rhs._M_future);
00899         _M_storage.swap(__rhs._M_storage);
00900       }
00901 
00902       // Retrieving the result
00903       future<_Res>
00904       get_future()
00905       { return future<_Res>(_M_future); }
00906 
00907       // Setting the result
00908       void
00909       set_value(const _Res& __r)
00910       {
00911         auto __setter = _State::__setter(this, __r);
00912         _M_future->_M_set_result(std::move(__setter));
00913       }
00914 
00915       void
00916       set_value(_Res&& __r)
00917       {
00918         auto __setter = _State::__setter(this, std::move(__r));
00919         _M_future->_M_set_result(std::move(__setter));
00920       }
00921 
00922       void
00923       set_exception(exception_ptr __p)
00924       {
00925         auto __setter = _State::__setter(__p, this);
00926         _M_future->_M_set_result(std::move(__setter));
00927       }
00928     };
00929 
00930   template<typename _Res>
00931     inline void
00932     swap(promise<_Res>& __x, promise<_Res>& __y)
00933     { __x.swap(__y); }
00934 
00935   template<typename _Res, typename _Alloc>
00936     struct uses_allocator<promise<_Res>, _Alloc>
00937     : public true_type { };
00938 
00939 
00940   /// Partial specialization for promise<R&>
00941   template<typename _Res>
00942     class promise<_Res&>
00943     {
00944       typedef __future_base::_State_base            _State;
00945       typedef __future_base::_Result<_Res&>         _Res_type;
00946       typedef typename __future_base::_Ptr<_Res_type>::type     _Ptr_type;
00947       template<typename, typename> friend class _State::_Setter;
00948 
00949       shared_ptr<_State>                        _M_future;
00950       _Ptr_type                                 _M_storage;
00951 
00952     public:
00953       promise()
00954       : _M_future(std::make_shared<_State>()),
00955     _M_storage(new _Res_type())
00956       { }
00957 
00958       promise(promise&& __rhs)
00959       : _M_future(std::move(__rhs._M_future)), 
00960     _M_storage(std::move(__rhs._M_storage))
00961       { }
00962 
00963       template<typename _Allocator>
00964         promise(allocator_arg_t, const _Allocator& __a)
00965         : _M_future(std::allocate_shared<_State>(__a)),
00966       _M_storage(__future_base::_S_allocate_result<_Res&>(__a))
00967         { }
00968 
00969       promise(const promise&) = delete;
00970 
00971       ~promise()
00972       {
00973         if (static_cast<bool>(_M_future) && !_M_future.unique())
00974           _M_future->_M_break_promise(std::move(_M_storage));
00975       }
00976 
00977       // Assignment
00978       promise&
00979       operator=(promise&& __rhs)
00980       {
00981         promise(std::move(__rhs)).swap(*this);
00982         return *this;
00983       }
00984 
00985       promise& operator=(const promise&) = delete;
00986 
00987       void
00988       swap(promise& __rhs)
00989       {
00990         _M_future.swap(__rhs._M_future);
00991         _M_storage.swap(__rhs._M_storage);
00992       }
00993 
00994       // Retrieving the result
00995       future<_Res&>
00996       get_future()
00997       { return future<_Res&>(_M_future); }
00998 
00999       // Setting the result
01000       void
01001       set_value(_Res& __r)
01002       {
01003         auto __setter = _State::__setter(this, __r);
01004         _M_future->_M_set_result(std::move(__setter));
01005       }
01006 
01007       void
01008       set_exception(exception_ptr __p)
01009       {
01010         auto __setter = _State::__setter(__p, this);
01011         _M_future->_M_set_result(std::move(__setter));
01012       }
01013     };
01014 
01015   /// Explicit specialization for promise<void>
01016   template<>
01017     class promise<void>
01018     {
01019       typedef __future_base::_State_base            _State;
01020       typedef __future_base::_Result<void>          _Res_type;
01021       typedef typename __future_base::_Ptr<_Res_type>::type     _Ptr_type;
01022       template<typename, typename> friend class _State::_Setter;
01023 
01024       shared_ptr<_State>                        _M_future;
01025       _Ptr_type                                 _M_storage;
01026 
01027     public:
01028       promise()
01029       : _M_future(std::make_shared<_State>()),
01030     _M_storage(new _Res_type())
01031       { }
01032 
01033       promise(promise&& __rhs)
01034       : _M_future(std::move(__rhs._M_future)),
01035     _M_storage(std::move(__rhs._M_storage))
01036       { }
01037 
01038       template<typename _Allocator>
01039         promise(allocator_arg_t, const _Allocator& __a)
01040         : _M_future(std::allocate_shared<_State>(__a)),
01041       _M_storage(__future_base::_S_allocate_result<void>(__a))
01042         { }
01043 
01044       promise(const promise&) = delete;
01045 
01046       ~promise()
01047       {
01048         if (static_cast<bool>(_M_future) && !_M_future.unique())
01049           _M_future->_M_break_promise(std::move(_M_storage));
01050       }
01051 
01052       // Assignment
01053       promise&
01054       operator=(promise&& __rhs)
01055       {
01056         promise(std::move(__rhs)).swap(*this);
01057         return *this;
01058       }
01059 
01060       promise& operator=(const promise&) = delete;
01061 
01062       void
01063       swap(promise& __rhs)
01064       {
01065         _M_future.swap(__rhs._M_future);
01066         _M_storage.swap(__rhs._M_storage);
01067       }
01068 
01069       // Retrieving the result
01070       future<void>
01071       get_future()
01072       { return future<void>(_M_future); }
01073 
01074       // Setting the result
01075       void set_value();
01076 
01077       void
01078       set_exception(exception_ptr __p)
01079       {
01080         auto __setter = _State::__setter(__p, this);
01081         _M_future->_M_set_result(std::move(__setter));
01082       }
01083     };
01084 
01085   // set void
01086   template<>
01087     struct __future_base::_State_base::_Setter<void, void>
01088     {
01089       promise<void>::_Ptr_type operator()()
01090       {
01091         _State_base::_S_check(_M_promise->_M_future);
01092         return std::move(_M_promise->_M_storage);
01093       }
01094 
01095       promise<void>*    _M_promise;
01096     };
01097 
01098   inline __future_base::_State_base::_Setter<void, void>
01099   __future_base::_State_base::__setter(promise<void>* __prom)
01100   {
01101     return _Setter<void, void>{ __prom };
01102   }
01103 
01104   inline void
01105   promise<void>::set_value()
01106   {
01107     auto __setter = _State::__setter(this);
01108     _M_future->_M_set_result(std::move(__setter));
01109   }
01110 
01111 
01112   template<typename _StateT, typename _Res>
01113     struct __future_base::_Task_setter
01114     {
01115       typename _StateT::_Ptr_type operator()()
01116       {
01117         __try
01118       {
01119         _M_state->_M_result->_M_set(_M_fn());
01120       }
01121     __catch(...)
01122       {
01123         _M_state->_M_result->_M_error = current_exception();
01124       }
01125         return std::move(_M_state->_M_result);
01126       }
01127       _StateT*                  _M_state;
01128       std::function<_Res()>     _M_fn;
01129     };
01130 
01131   template<typename _StateT>
01132     struct __future_base::_Task_setter<_StateT, void>
01133     {
01134       typename _StateT::_Ptr_type operator()()
01135       {
01136         __try
01137       {
01138         _M_fn();
01139       }
01140     __catch(...)
01141       {
01142         _M_state->_M_result->_M_error = current_exception();
01143       }
01144     return std::move(_M_state->_M_result);
01145       }
01146       _StateT*                  _M_state;
01147       std::function<void()>     _M_fn;
01148     };
01149 
01150   template<typename _Res, typename... _Args>
01151     struct __future_base::_Task_state<_Res(_Args...)> 
01152     : __future_base::_State_base
01153     {
01154       typedef _Res _Res_type;
01155 
01156       _Task_state(std::function<_Res(_Args...)> __task)
01157       : _M_result(new _Result<_Res>()), _M_task(std::move(__task))
01158       { }
01159 
01160       template<typename _Func, typename _Alloc>
01161         _Task_state(_Func&& __task, const _Alloc& __a)
01162         : _M_result(_S_allocate_result<_Res>(__a)),
01163       _M_task(allocator_arg, __a, std::move(__task))
01164         { }
01165 
01166       void
01167       _M_run(_Args... __args)
01168       {
01169         // bound arguments decay so wrap lvalue references
01170         auto __bound = std::bind<_Res>(std::ref(_M_task),
01171             _S_maybe_wrap_ref(std::forward<_Args>(__args))...);
01172         _Task_setter<_Task_state> __setter{ this, std::move(__bound) };
01173         _M_set_result(std::move(__setter));
01174       }
01175 
01176       template<typename, typename> friend class _Task_setter;
01177       typedef typename __future_base::_Ptr<_Result<_Res>>::type _Ptr_type;
01178       _Ptr_type _M_result;
01179       std::function<_Res(_Args...)> _M_task;
01180 
01181       template<typename _Tp>
01182         static reference_wrapper<_Tp>
01183         _S_maybe_wrap_ref(_Tp& __t)
01184         { return std::ref(__t); }
01185 
01186       template<typename _Tp>
01187         static typename enable_if<!is_lvalue_reference<_Tp>::value,
01188                         _Tp>::type&&
01189         _S_maybe_wrap_ref(_Tp&& __t)
01190         { return std::forward<_Tp>(__t); }
01191     };
01192 
01193   /// packaged_task
01194   template<typename _Res, typename... _ArgTypes>
01195     class packaged_task<_Res(_ArgTypes...)>
01196     {
01197       typedef __future_base::_Task_state<_Res(_ArgTypes...)>  _State_type;
01198       shared_ptr<_State_type>                   _M_state;
01199 
01200     public:
01201       typedef _Res result_type;
01202 
01203       // Construction and destruction
01204       packaged_task() { }
01205 
01206       template<typename _Fn>
01207         explicit
01208         packaged_task(const _Fn& __fn)
01209         : _M_state(std::make_shared<_State_type>(__fn))
01210         { }
01211 
01212       template<typename _Fn>
01213         explicit
01214         packaged_task(_Fn&& __fn)
01215         : _M_state(std::make_shared<_State_type>(std::move(__fn)))
01216         { }
01217 
01218       explicit
01219       packaged_task(_Res(*__fn)(_ArgTypes...))
01220       : _M_state(std::make_shared<_State_type>(__fn))
01221       { }
01222 
01223       template<typename _Fn, typename _Allocator>
01224         explicit
01225         packaged_task(allocator_arg_t __tag, const _Allocator& __a, _Fn __fn)
01226         : _M_state(std::allocate_shared<_State_type>(__a, std::move(__fn)))
01227         { }
01228 
01229       ~packaged_task()
01230       {
01231         if (static_cast<bool>(_M_state) && !_M_state.unique())
01232           _M_state->_M_break_promise(std::move(_M_state->_M_result));
01233       }
01234 
01235       // No copy
01236       packaged_task(packaged_task&) = delete;
01237       packaged_task& operator=(packaged_task&) = delete;
01238 
01239       // Move support
01240       packaged_task(packaged_task&& __other)
01241       { this->swap(__other); }
01242 
01243       packaged_task& operator=(packaged_task&& __other)
01244       {
01245         packaged_task(std::move(__other)).swap(*this);
01246         return *this;
01247       }
01248 
01249       void
01250       swap(packaged_task& __other)
01251       { _M_state.swap(__other._M_state); }
01252 
01253       bool
01254       valid() const
01255       { return static_cast<bool>(_M_state); }
01256 
01257       // Result retrieval
01258       future<_Res>
01259       get_future()
01260       { return future<_Res>(_M_state); }
01261 
01262       // Execution
01263       void
01264       operator()(_ArgTypes... __args)
01265       {
01266         __future_base::_State_base::_S_check(_M_state);
01267         _M_state->_M_run(std::forward<_ArgTypes>(__args)...);
01268       }
01269 
01270       void
01271       reset()
01272       {
01273         __future_base::_State_base::_S_check(_M_state);
01274         packaged_task(std::move(_M_state->_M_task)).swap(*this);
01275       }
01276     };
01277 
01278   /// swap
01279   template<typename _Res, typename... _ArgTypes>
01280     inline void
01281     swap(packaged_task<_Res(_ArgTypes...)>& __x,
01282      packaged_task<_Res(_ArgTypes...)>& __y)
01283     { __x.swap(__y); }
01284 
01285   template<typename _Res, typename _Alloc>
01286     struct uses_allocator<packaged_task<_Res>, _Alloc>
01287     : public true_type { };
01288 
01289 
01290   template<typename _Res>
01291     class __future_base::_Deferred_state : public __future_base::_State_base
01292     {
01293     public:
01294       typedef _Res _Res_type;
01295 
01296       explicit
01297       _Deferred_state(std::function<_Res()>&& __fn)
01298       : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn))
01299       { }
01300 
01301     private:
01302       template<typename, typename> friend class _Task_setter;
01303       typedef typename __future_base::_Ptr<_Result<_Res>>::type _Ptr_type;
01304       _Ptr_type _M_result;
01305       std::function<_Res()> _M_fn;
01306 
01307       virtual void
01308       _M_run_deferred()
01309       {
01310         _Task_setter<_Deferred_state> __setter{ this, _M_fn };
01311         // safe to call multiple times so ignore failure
01312         _M_set_result(std::move(__setter), true);
01313       }
01314     };
01315 
01316   template<typename _Res>
01317     class __future_base::_Async_state : public __future_base::_State_base
01318     {
01319     public:
01320       typedef _Res _Res_type;
01321 
01322       explicit 
01323       _Async_state(std::function<_Res()>&& __fn)
01324       : _M_result(new _Result<_Res>()), _M_fn(std::move(__fn)),
01325     _M_thread(mem_fn(&_Async_state::_M_do_run), this)
01326       { }
01327 
01328       ~_Async_state() { _M_thread.join(); }
01329 
01330     private:
01331       void _M_do_run()
01332       {
01333         _Task_setter<_Async_state> __setter{ this, std::move(_M_fn) };
01334         _M_set_result(std::move(__setter));
01335       }
01336 
01337       template<typename, typename> friend class _Task_setter;
01338       typedef typename __future_base::_Ptr<_Result<_Res>>::type _Ptr_type;
01339       _Ptr_type _M_result;
01340       std::function<_Res()> _M_fn;
01341       thread _M_thread;
01342     };
01343 
01344   /// async 
01345   template<typename _Fn, typename... _Args>
01346     future<typename result_of<_Fn(_Args...)>::type>
01347     async(launch __policy, _Fn&& __fn, _Args&&... __args)
01348     {
01349       typedef typename result_of<_Fn(_Args...)>::type result_type;
01350       std::shared_ptr<__future_base::_State_base> __state;
01351       if (__policy == launch::async)
01352     {
01353       typedef typename __future_base::_Async_state<result_type> _State;
01354       __state = std::make_shared<_State>(std::bind<result_type>(
01355               std::forward<_Fn>(__fn), std::forward<_Args>(__args)...));
01356     }
01357       else
01358     {
01359       typedef typename __future_base::_Deferred_state<result_type> _State;
01360       __state = std::make_shared<_State>(std::bind<result_type>(
01361               std::forward<_Fn>(__fn), std::forward<_Args>(__args)...));
01362     }
01363       return future<result_type>(__state);
01364     }
01365 
01366   /// async, potential overload
01367   template<typename _Fn, typename... _Args>
01368     inline typename
01369     enable_if<!is_same<typename decay<_Fn>::type, launch>::value,
01370               future<decltype(std::declval<_Fn>()(std::declval<_Args>()...))>
01371              >::type
01372     async(_Fn&& __fn, _Args&&... __args)
01373     {
01374       return async(launch::any, std::forward<_Fn>(__fn),
01375            std::forward<_Args>(__args)...);
01376     }
01377 
01378 #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
01379        // && _GLIBCXX_ATOMIC_BUILTINS_4
01380 
01381   // @} group futures
01382 _GLIBCXX_END_NAMESPACE_VERSION
01383 } // namespace
01384 
01385 #endif // __GXX_EXPERIMENTAL_CXX0X__
01386 
01387 #endif // _GLIBCXX_FUTURE