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() = default;
00164       _Result_base(const _Result_base&) = delete;
00165       _Result_base& operator=(const _Result_base&) = delete;
00166 
00167       // _M_destroy() allows derived classes to control deallocation
00168       virtual void _M_destroy() = 0;
00169 
00170       struct _Deleter
00171       {
00172     void operator()(_Result_base* __fr) const { __fr->_M_destroy(); }
00173       };
00174 
00175     protected:
00176       ~_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     /// Shared state between a promise and one or more associated futures.
00277     class _State
00278     {
00279       typedef _Ptr<_Result_base>::type _Ptr_type;
00280 
00281       _Ptr_type         _M_result;
00282       mutex                 _M_mutex;
00283       condition_variable    _M_cond;
00284       atomic_flag           _M_retrieved;
00285       once_flag         _M_once;
00286 
00287     public:
00288       _State() : _M_result(), _M_retrieved(ATOMIC_FLAG_INIT) { }
00289 
00290       _State(const _State&) = delete;
00291       _State& operator=(const _State&) = delete;
00292 
00293       _Result_base&
00294       wait()
00295       {
00296     _M_run_deferred();
00297     unique_lock<mutex> __lock(_M_mutex);
00298     if (!_M_ready())
00299       _M_cond.wait(__lock, std::bind<bool>(&_State::_M_ready, this));
00300     return *_M_result;
00301       }
00302 
00303       template<typename _Rep, typename _Period>
00304         bool
00305         wait_for(const chrono::duration<_Rep, _Period>& __rel)
00306         {
00307       unique_lock<mutex> __lock(_M_mutex);
00308       auto __bound = std::bind<bool>(&_State::_M_ready, this);
00309       return _M_ready() || _M_cond.wait_for(__lock, __rel, __bound);
00310     }
00311 
00312       template<typename _Clock, typename _Duration>
00313         bool
00314         wait_until(const chrono::time_point<_Clock, _Duration>& __abs)
00315         {
00316       unique_lock<mutex> __lock(_M_mutex);
00317       auto __bound = std::bind<bool>(&_State::_M_ready, this);
00318       return _M_ready() || _M_cond.wait_until(__lock, __abs, __bound);
00319     }
00320 
00321       void
00322       _M_set_result(function<_Ptr_type()> __res, bool __ignore_failure = false)
00323       {
00324         bool __set = __ignore_failure;
00325         // all calls to this function are serialized,
00326         // side-effects of invoking __res only happen once
00327         call_once(_M_once, &_State::_M_do_set, this, ref(__res),
00328             ref(__set));
00329         if (!__set)
00330           __throw_future_error(int(future_errc::promise_already_satisfied));
00331       }
00332 
00333       void
00334       _M_break_promise(_Ptr_type __res)
00335       {
00336     if (static_cast<bool>(__res))
00337       {
00338         error_code __ec(make_error_code(future_errc::broken_promise));
00339         __res->_M_error = copy_exception(future_error(__ec));
00340         {
00341           lock_guard<mutex> __lock(_M_mutex);
00342           _M_result.swap(__res);
00343         }
00344         _M_cond.notify_all();
00345       }
00346       }
00347 
00348       // Called when this object is passed to a future.
00349       void
00350       _M_set_retrieved_flag()
00351       {
00352     if (_M_retrieved.test_and_set())
00353       __throw_future_error(int(future_errc::future_already_retrieved));
00354       }
00355 
00356       template<typename _Res, typename _Arg>
00357         struct _Setter;
00358 
00359       // set lvalues
00360       template<typename _Res, typename _Arg>
00361         struct _Setter<_Res, _Arg&>
00362         {
00363           // check this is only used by promise<R>::set_value(const R&)
00364           // or promise<R>::set_value(R&)
00365           static_assert(is_same<_Res, _Arg&>::value  // promise<R&>
00366               || is_same<const _Res, _Arg>::value,  // promise<R>
00367               "Invalid specialisation");
00368 
00369           typename promise<_Res>::_Ptr_type operator()()
00370           {
00371             _State::_S_check(_M_promise->_M_future);
00372             _M_promise->_M_storage->_M_set(_M_arg);
00373             return std::move(_M_promise->_M_storage);
00374           }
00375           promise<_Res>*    _M_promise;
00376           _Arg&             _M_arg;
00377         };
00378 
00379       // set rvalues
00380       template<typename _Res>
00381         struct _Setter<_Res, _Res&&>
00382         {
00383           typename promise<_Res>::_Ptr_type operator()()
00384           {
00385             _State::_S_check(_M_promise->_M_future);
00386             _M_promise->_M_storage->_M_set(std::move(_M_arg));
00387             return std::move(_M_promise->_M_storage);
00388           }
00389           promise<_Res>*    _M_promise;
00390           _Res&             _M_arg;
00391         };
00392 
00393       struct __exception_ptr_tag { };
00394 
00395       // set exceptions
00396       template<typename _Res>
00397         struct _Setter<_Res, __exception_ptr_tag>
00398         {
00399           typename promise<_Res>::_Ptr_type operator()()
00400           {
00401             _State::_S_check(_M_promise->_M_future);
00402             _M_promise->_M_storage->_M_error = _M_ex;
00403             return std::move(_M_promise->_M_storage);
00404           }
00405 
00406           promise<_Res>*   _M_promise;
00407           exception_ptr&    _M_ex;
00408         };
00409 
00410       template<typename _Res, typename _Arg>
00411         static _Setter<_Res, _Arg&&>
00412         __setter(promise<_Res>* __prom, _Arg&& __arg)
00413         {
00414           return _Setter<_Res, _Arg&&>{ __prom, __arg };
00415         }
00416 
00417       template<typename _Res>
00418         static _Setter<_Res, __exception_ptr_tag>
00419         __setter(exception_ptr& __ex, promise<_Res>* __prom)
00420         {
00421           return _Setter<_Res, __exception_ptr_tag>{ __prom, __ex };
00422         }
00423 
00424       static _Setter<void, void>
00425       __setter(promise<void>* __prom);
00426 
00427       template<typename _Tp>
00428         static bool
00429         _S_check(const shared_ptr<_Tp>& __p)
00430         {
00431           if (!static_cast<bool>(__p))
00432             __throw_future_error((int)future_errc::no_state);
00433         }
00434 
00435     private:
00436       void
00437       _M_do_set(function<_Ptr_type()>& __f, bool& __set)
00438       {
00439         _Ptr_type __res = __f();
00440         {
00441           lock_guard<mutex> __lock(_M_mutex);
00442           _M_result.swap(__res);
00443         }
00444         _M_cond.notify_all();
00445         __set = true;
00446       }
00447 
00448       bool _M_ready() const { return static_cast<bool>(_M_result); }
00449 
00450       virtual void _M_run_deferred() { }
00451     };
00452 
00453     template<typename _Res>
00454       class _Deferred_state;
00455 
00456     template<typename _Res>
00457       class _Async_state;
00458 
00459     template<typename _Signature>
00460       class _Task_state;
00461 
00462     template<typename _StateT, typename _Res = typename _StateT::_Res_type>
00463       struct _Task_setter;
00464   };
00465 
00466   inline __future_base::_Result_base::~_Result_base() = default;
00467 
00468   /// Partial specialization for reference types.
00469   template<typename _Res>
00470     struct __future_base::_Result<_Res&> : __future_base::_Result_base
00471     {
00472       _Result() : _M_value_ptr() { }
00473 
00474       void _M_set(_Res& __res) { _M_value_ptr = &__res; }
00475 
00476       _Res& _M_get() { return *_M_value_ptr; }
00477 
00478     private:
00479       _Res*             _M_value_ptr;
00480       
00481       void _M_destroy() { delete this; }
00482     };
00483 
00484   /// Explicit specialization for void.
00485   template<>
00486     struct __future_base::_Result<void> : __future_base::_Result_base
00487     {
00488     private:
00489       void _M_destroy() { delete this; }
00490     };
00491 
00492 
00493   /// Common implementation for future and shared_future.
00494   template<typename _Res>
00495     class __basic_future : public __future_base
00496     {
00497     protected:
00498       typedef shared_ptr<_State>        __state_type;
00499       typedef __future_base::_Result<_Res>& __result_type;
00500 
00501     private:
00502       __state_type      _M_state;
00503 
00504     public:
00505       // Disable copying.
00506       __basic_future(const __basic_future&) = delete;
00507       __basic_future& operator=(const __basic_future&) = delete;
00508 
00509       bool 
00510       valid() const { return static_cast<bool>(_M_state); }
00511 
00512       void 
00513       wait() const
00514       {
00515         _State::_S_check(_M_state);
00516         _M_state->wait();
00517       }
00518 
00519       template<typename _Rep, typename _Period>
00520         bool
00521         wait_for(const chrono::duration<_Rep, _Period>& __rel) const
00522         {
00523           _State::_S_check(_M_state);
00524           return _M_state->wait_for(__rel);
00525         }
00526 
00527       template<typename _Clock, typename _Duration>
00528         bool
00529         wait_until(const chrono::time_point<_Clock, _Duration>& __abs) const
00530         {
00531           _State::_S_check(_M_state);
00532           return _M_state->wait_until(__abs);
00533         }
00534 
00535     protected:
00536       /// Wait for the state to be ready and rethrow any stored exception
00537       __result_type
00538       _M_get_result()
00539       {
00540         _State::_S_check(_M_state);
00541         _Result_base& __res = _M_state->wait();
00542         if (!(__res._M_error == 0))
00543           rethrow_exception(__res._M_error);
00544         return static_cast<__result_type>(__res);
00545       }
00546 
00547       void _M_swap(__basic_future& __that)
00548       {
00549         _M_state.swap(__that._M_state);
00550       }
00551 
00552       // Construction of a future by promise::get_future()
00553       explicit
00554       __basic_future(const __state_type& __state) : _M_state(__state)
00555       {
00556         _State::_S_check(_M_state);
00557         _M_state->_M_set_retrieved_flag();
00558       }
00559 
00560       // Copy construction from a shared_future
00561       explicit
00562       __basic_future(const shared_future<_Res>&);
00563 
00564       // Move construction from a shared_future
00565       explicit
00566       __basic_future(shared_future<_Res>&&);
00567 
00568       // Move construction from a future
00569       explicit
00570       __basic_future(future<_Res>&&);
00571 
00572       constexpr __basic_future() : _M_state() { }
00573 
00574       struct _Reset
00575       {
00576         explicit _Reset(__basic_future& __fut) : _M_fut(__fut) { }
00577         ~_Reset() { _M_fut._M_state.reset(); }
00578         __basic_future& _M_fut;
00579       };
00580     };
00581 
00582 
00583   /// Primary template for future.
00584   template<typename _Res>
00585     class future : public __basic_future<_Res>
00586     {
00587       friend class promise<_Res>;
00588       template<typename> friend class packaged_task;
00589       template<typename _Fn, typename... _Args>
00590         friend future<typename result_of<_Fn(_Args...)>::type>
00591         async(launch, _Fn&&, _Args&&...);
00592 
00593       typedef __basic_future<_Res> _Base_type;
00594       typedef typename _Base_type::__state_type __state_type;
00595 
00596       explicit
00597       future(const __state_type& __state) : _Base_type(__state) { }
00598 
00599     public:
00600       constexpr future() : _Base_type() { }
00601 
00602       /// Move constructor
00603       future(future&& __uf) : _Base_type(std::move(__uf)) { }
00604 
00605       // Disable copying
00606       future(const future&) = delete;
00607       future& operator=(const future&) = delete;
00608 
00609       future& operator=(future&& __fut)
00610       {
00611         future(std::move(__fut))._M_swap(*this);
00612         return *this;
00613       }
00614 
00615       /// Retrieving the value
00616       _Res
00617       get()
00618       {
00619         typename _Base_type::_Reset __reset(*this);
00620         return std::move(this->_M_get_result()._M_value());
00621       }
00622     };
00623  
00624   /// Partial specialization for future<R&>
00625   template<typename _Res>
00626     class future<_Res&> : public __basic_future<_Res&>
00627     {
00628       friend class promise<_Res&>;
00629       template<typename> friend class packaged_task;
00630       template<typename _Fn, typename... _Args>
00631         friend future<typename result_of<_Fn(_Args...)>::type>
00632         async(launch, _Fn&&, _Args&&...);
00633 
00634       typedef __basic_future<_Res&> _Base_type;
00635       typedef typename _Base_type::__state_type __state_type;
00636 
00637       explicit
00638       future(const __state_type& __state) : _Base_type(__state) { }
00639 
00640     public:
00641       constexpr future() : _Base_type() { }
00642 
00643       /// Move constructor
00644       future(future&& __uf) : _Base_type(std::move(__uf)) { }
00645 
00646       // Disable copying
00647       future(const future&) = delete;
00648       future& operator=(const future&) = delete;
00649 
00650       future& operator=(future&& __fut)
00651       {
00652         future(std::move(__fut))._M_swap(*this);
00653         return *this;
00654       }
00655 
00656       /// Retrieving the value
00657       _Res& 
00658       get()
00659       {
00660         typename _Base_type::_Reset __reset(*this);
00661         return this->_M_get_result()._M_get();
00662       }
00663     };
00664 
00665   /// Explicit specialization for future<void>
00666   template<>
00667     class future<void> : public __basic_future<void>
00668     {
00669       friend class promise<void>;
00670       template<typename> friend class packaged_task;
00671       template<typename _Fn, typename... _Args>
00672         friend future<typename result_of<_Fn(_Args...)>::type>
00673         async(launch, _Fn&&, _Args&&...);
00674 
00675       typedef __basic_future<void> _Base_type;
00676       typedef typename _Base_type::__state_type __state_type;
00677 
00678       explicit
00679       future(const __state_type& __state) : _Base_type(__state) { }
00680 
00681     public:
00682       constexpr future() : _Base_type() { }
00683 
00684       /// Move constructor
00685       future(future&& __uf) : _Base_type(std::move(__uf)) { }
00686 
00687       // Disable copying
00688       future(const future&) = delete;
00689       future& operator=(const future&) = delete;
00690 
00691       future& operator=(future&& __fut)
00692       {
00693         future(std::move(__fut))._M_swap(*this);
00694         return *this;
00695       }
00696 
00697       /// Retrieving the value
00698       void 
00699       get()
00700       {
00701         typename _Base_type::_Reset __reset(*this);
00702         this->_M_get_result();
00703       }
00704     };
00705 
00706 
00707   /// Primary template for shared_future.
00708   template<typename _Res>
00709     class shared_future : public __basic_future<_Res>
00710     {
00711       typedef __basic_future<_Res> _Base_type;
00712 
00713     public:
00714       constexpr shared_future() : _Base_type() { }
00715 
00716       /// Copy constructor
00717       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
00718 
00719       /// Construct from a future rvalue
00720       shared_future(future<_Res>&& __uf)
00721       : _Base_type(std::move(__uf))
00722       { }
00723 
00724       /// Construct from a shared_future rvalue
00725       shared_future(shared_future&& __sf)
00726       : _Base_type(std::move(__sf))
00727       { }
00728 
00729       shared_future& operator=(const shared_future& __sf)
00730       {
00731         shared_future(__sf)._M_swap(*this);
00732         return *this;
00733       }
00734 
00735       shared_future& operator=(shared_future&& __sf)
00736       {
00737         shared_future(std::move(__sf))._M_swap(*this);
00738         return *this;
00739       }
00740 
00741       /// Retrieving the value
00742       const _Res&
00743       get()
00744       {
00745     typename _Base_type::__result_type __r = this->_M_get_result();
00746     _Res& __rs(__r._M_value());
00747     return __rs;
00748       }
00749     };
00750  
00751   /// Partial specialization for shared_future<R&>
00752   template<typename _Res>
00753     class shared_future<_Res&> : public __basic_future<_Res&>
00754     {
00755       typedef __basic_future<_Res&>           _Base_type;
00756 
00757     public:
00758       constexpr shared_future() : _Base_type() { }
00759 
00760       /// Copy constructor
00761       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
00762 
00763       /// Construct from a future rvalue
00764       shared_future(future<_Res&>&& __uf)
00765       : _Base_type(std::move(__uf))
00766       { }
00767 
00768       /// Construct from a shared_future rvalue
00769       shared_future(shared_future&& __sf)
00770       : _Base_type(std::move(__sf))
00771       { }
00772 
00773       shared_future& operator=(const shared_future& __sf)
00774       {
00775         shared_future(__sf)._M_swap(*this);
00776         return *this;
00777       }
00778 
00779       shared_future& operator=(shared_future&& __sf)
00780       {
00781         shared_future(std::move(__sf))._M_swap(*this);
00782         return *this;
00783       }
00784 
00785       /// Retrieving the value
00786       _Res& 
00787       get() { return this->_M_get_result()._M_get(); }
00788     };
00789 
00790   /// Explicit specialization for shared_future<void>
00791   template<>
00792     class shared_future<void> : public __basic_future<void>
00793     {
00794       typedef __basic_future<void> _Base_type;
00795 
00796     public:
00797       constexpr shared_future() : _Base_type() { }
00798 
00799       /// Copy constructor
00800       shared_future(const shared_future& __sf) : _Base_type(__sf) { }
00801 
00802       /// Construct from a future rvalue
00803       shared_future(future<void>&& __uf)
00804       : _Base_type(std::move(__uf))
00805       { }
00806 
00807       /// Construct from a shared_future rvalue
00808       shared_future(shared_future&& __sf)
00809       : _Base_type(std::move(__sf))
00810       { }
00811 
00812       shared_future& operator=(const shared_future& __sf)
00813       {
00814         shared_future(__sf)._M_swap(*this);
00815         return *this;
00816       }
00817 
00818       shared_future& operator=(shared_future&& __sf)
00819       {
00820         shared_future(std::move(__sf))._M_swap(*this);
00821         return *this;
00822       }
00823 
00824       // Retrieving the value
00825       void 
00826       get() { this->_M_get_result(); }
00827     };
00828 
00829   // Now we can define the protected __basic_future constructors.
00830   template<typename _Res>
00831     inline __basic_future<_Res>::
00832     __basic_future(const shared_future<_Res>& __sf)
00833     : _M_state(__sf._M_state)
00834     { }
00835 
00836   template<typename _Res>
00837     inline __basic_future<_Res>::
00838     __basic_future(shared_future<_Res>&& __sf)
00839     : _M_state(std::move(__sf._M_state))
00840     { }
00841 
00842   template<typename _Res>
00843     inline __basic_future<_Res>::
00844     __basic_future(future<_Res>&& __uf)
00845     : _M_state(std::move(__uf._M_state))
00846     { }
00847 
00848 
00849   /// Primary template for promise
00850   template<typename _Res>
00851     class promise
00852     {
00853       typedef __future_base::_State         _State;
00854       typedef __future_base::_Result<_Res>  _Res_type;
00855       typedef typename __future_base::_Ptr<_Res_type>::type _Ptr_type;
00856       template<typename, typename> friend class _State::_Setter;
00857       
00858       shared_ptr<_State>                        _M_future;
00859       _Ptr_type                                 _M_storage;
00860 
00861     public:
00862       promise()
00863       : _M_future(std::make_shared<_State>()),
00864     _M_storage(new _Res_type())
00865       { }
00866 
00867       promise(promise&& __rhs)
00868       : _M_future(std::move(__rhs._M_future)),
00869     _M_storage(std::move(__rhs._M_storage))
00870       { }
00871 
00872       template<typename _Allocator>
00873         promise(allocator_arg_t, const _Allocator& __a)
00874         : _M_future(std::allocate_shared<_State>(__a)),
00875       _M_storage(__future_base::_S_allocate_result<_Res>(__a))
00876         { }
00877 
00878       promise(const promise&) = delete;
00879 
00880       ~promise()
00881       {
00882         if (static_cast<bool>(_M_future) && !_M_future.unique())
00883           _M_future->_M_break_promise(std::move(_M_storage));
00884       }
00885 
00886       // Assignment
00887       promise&
00888       operator=(promise&& __rhs)
00889       {
00890         promise(std::move(__rhs)).swap(*this);
00891         return *this;
00892       }
00893 
00894       promise& operator=(const promise&) = delete;
00895 
00896       void
00897       swap(promise& __rhs)
00898       {
00899         _M_future.swap(__rhs._M_future);
00900         _M_storage.swap(__rhs._M_storage);
00901       }
00902 
00903       // Retrieving the result
00904       future<_Res>
00905       get_future()
00906       { return future<_Res>(_M_future); }
00907 
00908       // Setting the result
00909       void
00910       set_value(const _Res& __r)
00911       {
00912         auto __setter = _State::__setter(this, __r);
00913         _M_future->_M_set_result(std::move(__setter));
00914       }
00915 
00916       void
00917       set_value(_Res&& __r)
00918       {
00919         auto __setter = _State::__setter(this, std::move(__r));
00920         _M_future->_M_set_result(std::move(__setter));
00921       }
00922 
00923       void
00924       set_exception(exception_ptr __p)
00925       {
00926         auto __setter = _State::__setter(__p, this);
00927         _M_future->_M_set_result(std::move(__setter));
00928       }
00929     };
00930 
00931   template<typename _Res>
00932     inline void
00933     swap(promise<_Res>& __x, promise<_Res>& __y)
00934     { __x.swap(__y); }
00935 
00936   template<typename _Res, typename _Alloc>
00937     struct uses_allocator<promise<_Res>, _Alloc>
00938     : public true_type { };
00939 
00940 
00941   /// Partial specialization for promise<R&>
00942   template<typename _Res>
00943     class promise<_Res&>
00944     {
00945       typedef __future_base::_State         _State;
00946       typedef __future_base::_Result<_Res&> _Res_type;
00947       typedef typename __future_base::_Ptr<_Res_type>::type _Ptr_type;
00948       template<typename, typename> friend class _State::_Setter;
00949 
00950       shared_ptr<_State>                        _M_future;
00951       _Ptr_type                                 _M_storage;
00952 
00953     public:
00954       promise()
00955       : _M_future(std::make_shared<_State>()),
00956     _M_storage(new _Res_type())
00957       { }
00958 
00959       promise(promise&& __rhs)
00960       : _M_future(std::move(__rhs._M_future)), 
00961     _M_storage(std::move(__rhs._M_storage))
00962       { }
00963 
00964       template<typename _Allocator>
00965         promise(allocator_arg_t, const _Allocator& __a)
00966         : _M_future(std::allocate_shared<_State>(__a)),
00967       _M_storage(__future_base::_S_allocate_result<_Res&>(__a))
00968         { }
00969 
00970       promise(const promise&) = delete;
00971 
00972       ~promise()
00973       {
00974         if (static_cast<bool>(_M_future) && !_M_future.unique())
00975           _M_future->_M_break_promise(std::move(_M_storage));
00976       }
00977 
00978       // Assignment
00979       promise&
00980       operator=(promise&& __rhs)
00981       {
00982         promise(std::move(__rhs)).swap(*this);
00983         return *this;
00984       }
00985 
00986       promise& operator=(const promise&) = delete;
00987 
00988       void
00989       swap(promise& __rhs)
00990       {
00991         _M_future.swap(__rhs._M_future);
00992         _M_storage.swap(__rhs._M_storage);
00993       }
00994 
00995       // Retrieving the result
00996       future<_Res&>
00997       get_future()
00998       { return future<_Res&>(_M_future); }
00999 
01000       // Setting the result
01001       void
01002       set_value(_Res& __r)
01003       {
01004         auto __setter = _State::__setter(this, __r);
01005         _M_future->_M_set_result(std::move(__setter));
01006       }
01007 
01008       void
01009       set_exception(exception_ptr __p)
01010       {
01011         auto __setter = _State::__setter(__p, this);
01012         _M_future->_M_set_result(std::move(__setter));
01013       }
01014     };
01015 
01016   /// Explicit specialization for promise<void>
01017   template<>
01018     class promise<void>
01019     {
01020       typedef __future_base::_State         _State;
01021       typedef __future_base::_Result<void>  _Res_type;
01022       typedef typename __future_base::_Ptr<_Res_type>::type _Ptr_type;
01023       template<typename, typename> friend class _State::_Setter;
01024 
01025       shared_ptr<_State>                        _M_future;
01026       _Ptr_type                                 _M_storage;
01027 
01028     public:
01029       promise()
01030       : _M_future(std::make_shared<_State>()),
01031     _M_storage(new _Res_type())
01032       { }
01033 
01034       promise(promise&& __rhs)
01035       : _M_future(std::move(__rhs._M_future)),
01036     _M_storage(std::move(__rhs._M_storage))
01037       { }
01038 
01039       template<typename _Allocator>
01040         promise(allocator_arg_t, const _Allocator& __a)
01041         : _M_future(std::allocate_shared<_State>(__a)),
01042       _M_storage(__future_base::_S_allocate_result<void>(__a))
01043         { }
01044 
01045       promise(const promise&) = delete;
01046 
01047       ~promise()
01048       {
01049         if (static_cast<bool>(_M_future) && !_M_future.unique())
01050           _M_future->_M_break_promise(std::move(_M_storage));
01051       }
01052 
01053       // Assignment
01054       promise&
01055       operator=(promise&& __rhs)
01056       {
01057         promise(std::move(__rhs)).swap(*this);
01058         return *this;
01059       }
01060 
01061       promise& operator=(const promise&) = delete;
01062 
01063       void
01064       swap(promise& __rhs)
01065       {
01066         _M_future.swap(__rhs._M_future);
01067         _M_storage.swap(__rhs._M_storage);
01068       }
01069 
01070       // Retrieving the result
01071       future<void>
01072       get_future()
01073       { return future<void>(_M_future); }
01074 
01075       // Setting the result
01076       void set_value();
01077 
01078       void
01079       set_exception(exception_ptr __p)
01080       {
01081         auto __setter = _State::__setter(__p, this);
01082         _M_future->_M_set_result(std::move(__setter));
01083       }
01084     };
01085 
01086   // set void
01087   template<>
01088     struct __future_base::_State::_Setter<void, void>
01089     {
01090       promise<void>::_Ptr_type operator()()
01091       {
01092         _State::_S_check(_M_promise->_M_future);
01093         return std::move(_M_promise->_M_storage);
01094       }
01095 
01096       promise<void>*    _M_promise;
01097     };
01098 
01099   inline __future_base::_State::_Setter<void, void>
01100   __future_base::_State::__setter(promise<void>* __prom)
01101   {
01102     return _Setter<void, void>{ __prom };
01103   }
01104 
01105   inline void
01106   promise<void>::set_value()
01107   {
01108     auto __setter = _State::__setter(this);
01109     _M_future->_M_set_result(std::move(__setter));
01110   }
01111 
01112 
01113   template<typename _StateT, typename _Res>
01114     struct __future_base::_Task_setter
01115     {
01116       typename _StateT::_Ptr_type operator()()
01117       {
01118         __try
01119       {
01120         _M_state->_M_result->_M_set(_M_fn());
01121       }
01122     __catch(...)
01123       {
01124         _M_state->_M_result->_M_error = current_exception();
01125       }
01126         return std::move(_M_state->_M_result);
01127       }
01128       _StateT*                  _M_state;
01129       std::function<_Res()>     _M_fn;
01130     };
01131 
01132   template<typename _StateT>
01133     struct __future_base::_Task_setter<_StateT, void>
01134     {
01135       typename _StateT::_Ptr_type operator()()
01136       {
01137         __try
01138       {
01139         _M_fn();
01140       }
01141     __catch(...)
01142       {
01143         _M_state->_M_result->_M_error = current_exception();
01144       }
01145     return std::move(_M_state->_M_result);
01146       }
01147       _StateT*                  _M_state;
01148       std::function<void()>     _M_fn;
01149     };
01150 
01151   template<typename _Res, typename... _Args>
01152     struct __future_base::_Task_state<_Res(_Args...)> : __future_base::_State
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::_S_check(_M_state);
01267         _M_state->_M_run(std::forward<_ArgTypes>(__args)...);
01268       }
01269 
01270       void
01271       reset()
01272       {
01273         __future_base::_State::_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
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
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> __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