1// <thread> -*- C++ -*-
2
3// Copyright (C) 2008-2018 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file include/thread
26 *  This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_THREAD
30#define _GLIBCXX_THREAD 1
31
32#pragma GCC system_header
33
34#if __cplusplus < 201103L
35# include <bits/c++0x_warning.h>
36#else
37
38#include <chrono>
39#include <memory>
40#include <tuple>
41#include <cerrno>
42#include <bits/functexcept.h>
43#include <bits/functional_hash.h>
44#include <bits/invoke.h>
45#include <bits/gthr.h>
46
47#if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1)
48
49namespace std _GLIBCXX_VISIBILITY(default)
50{
51_GLIBCXX_BEGIN_NAMESPACE_VERSION
52
53  /**
54   * @defgroup threads Threads
55   * @ingroup concurrency
56   *
57   * Classes for thread support.
58   * @{
59   */
60
61  /// thread
62  class thread
63  {
64  public:
65    // Abstract base class for types that wrap arbitrary functors to be
66    // invoked in the new thread of execution.
67    struct _State
68    {
69      virtual ~_State();
70      virtual void _M_run() = 0;
71    };
72    using _State_ptr = unique_ptr<_State>;
73
74    typedef __gthread_t			native_handle_type;
75
76    /// thread::id
77    class id
78    {
79      native_handle_type	_M_thread;
80
81    public:
82      id() noexcept : _M_thread() { }
83
84      explicit
85      id(native_handle_type __id) : _M_thread(__id) { }
86
87    private:
88      friend class thread;
89      friend class hash<thread::id>;
90
91      friend bool
92      operator==(thread::id __x, thread::id __y) noexcept;
93
94      friend bool
95      operator<(thread::id __x, thread::id __y) noexcept;
96
97      template<class _CharT, class _Traits>
98	friend basic_ostream<_CharT, _Traits>&
99	operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id);
100    };
101
102  private:
103    id				_M_id;
104
105  public:
106    thread() noexcept = default;
107    // _GLIBCXX_RESOLVE_LIB_DEFECTS
108    // 2097.  packaged_task constructors should be constrained
109    thread(thread&) = delete;
110    thread(const thread&) = delete;
111    thread(const thread&&) = delete;
112
113    thread(thread&& __t) noexcept
114    { swap(__t); }
115
116    template<typename _Callable, typename... _Args>
117      explicit
118      thread(_Callable&& __f, _Args&&... __args)
119      {
120#ifdef GTHR_ACTIVE_PROXY
121	// Create a reference to pthread_create, not just the gthr weak symbol.
122	auto __depend = reinterpret_cast<void(*)()>(&pthread_create);
123#else
124	auto __depend = nullptr;
125#endif
126        _M_start_thread(_S_make_state(
127	      __make_invoker(std::forward<_Callable>(__f),
128			     std::forward<_Args>(__args)...)),
129	    __depend);
130      }
131
132    ~thread()
133    {
134      if (joinable())
135	std::terminate();
136    }
137
138    thread& operator=(const thread&) = delete;
139
140    thread& operator=(thread&& __t) noexcept
141    {
142      if (joinable())
143	std::terminate();
144      swap(__t);
145      return *this;
146    }
147
148    void
149    swap(thread& __t) noexcept
150    { std::swap(_M_id, __t._M_id); }
151
152    bool
153    joinable() const noexcept
154    { return !(_M_id == id()); }
155
156    void
157    join();
158
159    void
160    detach();
161
162    thread::id
163    get_id() const noexcept
164    { return _M_id; }
165
166    /** @pre thread is joinable
167     */
168    native_handle_type
169    native_handle()
170    { return _M_id._M_thread; }
171
172    // Returns a value that hints at the number of hardware thread contexts.
173    static unsigned int
174    hardware_concurrency() noexcept;
175
176  private:
177    template<typename _Callable>
178      struct _State_impl : public _State
179      {
180	_Callable		_M_func;
181
182	_State_impl(_Callable&& __f) : _M_func(std::forward<_Callable>(__f))
183	{ }
184
185	void
186	_M_run() { _M_func(); }
187      };
188
189    void
190    _M_start_thread(_State_ptr, void (*)());
191
192    template<typename _Callable>
193      static _State_ptr
194      _S_make_state(_Callable&& __f)
195      {
196	using _Impl = _State_impl<_Callable>;
197	return _State_ptr{new _Impl{std::forward<_Callable>(__f)}};
198      }
199#if _GLIBCXX_THREAD_ABI_COMPAT
200  public:
201    struct _Impl_base;
202    typedef shared_ptr<_Impl_base>	__shared_base_type;
203    struct _Impl_base
204    {
205      __shared_base_type	_M_this_ptr;
206      virtual ~_Impl_base() = default;
207      virtual void _M_run() = 0;
208    };
209
210  private:
211    void
212    _M_start_thread(__shared_base_type, void (*)());
213
214    void
215    _M_start_thread(__shared_base_type);
216#endif
217
218  private:
219    // A call wrapper that does INVOKE(forwarded tuple elements...)
220    template<typename _Tuple>
221      struct _Invoker
222      {
223	_Tuple _M_t;
224
225	template<size_t _Index>
226	  static __tuple_element_t<_Index, _Tuple>&&
227	  _S_declval();
228
229	template<size_t... _Ind>
230	  auto
231	  _M_invoke(_Index_tuple<_Ind...>)
232	  noexcept(noexcept(std::__invoke(_S_declval<_Ind>()...)))
233	  -> decltype(std::__invoke(_S_declval<_Ind>()...))
234	  { return std::__invoke(std::get<_Ind>(std::move(_M_t))...); }
235
236	using _Indices
237	  = typename _Build_index_tuple<tuple_size<_Tuple>::value>::__type;
238
239	auto
240	operator()()
241	noexcept(noexcept(std::declval<_Invoker&>()._M_invoke(_Indices())))
242	-> decltype(std::declval<_Invoker&>()._M_invoke(_Indices()))
243	{ return _M_invoke(_Indices()); }
244      };
245
246    template<typename... _Tp>
247      using __decayed_tuple = tuple<typename std::decay<_Tp>::type...>;
248
249  public:
250    // Returns a call wrapper that stores
251    // tuple{DECAY_COPY(__callable), DECAY_COPY(__args)...}.
252    template<typename _Callable, typename... _Args>
253      static _Invoker<__decayed_tuple<_Callable, _Args...>>
254      __make_invoker(_Callable&& __callable, _Args&&... __args)
255      {
256	return { __decayed_tuple<_Callable, _Args...>{
257	    std::forward<_Callable>(__callable), std::forward<_Args>(__args)...
258	} };
259      }
260  };
261
262  inline void
263  swap(thread& __x, thread& __y) noexcept
264  { __x.swap(__y); }
265
266  inline bool
267  operator==(thread::id __x, thread::id __y) noexcept
268  {
269    // pthread_equal is undefined if either thread ID is not valid, so we
270    // can't safely use __gthread_equal on default-constructed values (nor
271    // the non-zero value returned by this_thread::get_id() for
272    // single-threaded programs using GNU libc). Assume EqualityComparable.
273    return __x._M_thread == __y._M_thread;
274  }
275
276  inline bool
277  operator!=(thread::id __x, thread::id __y) noexcept
278  { return !(__x == __y); }
279
280  inline bool
281  operator<(thread::id __x, thread::id __y) noexcept
282  {
283    // Pthreads doesn't define any way to do this, so we just have to
284    // assume native_handle_type is LessThanComparable.
285    return __x._M_thread < __y._M_thread;
286  }
287
288  inline bool
289  operator<=(thread::id __x, thread::id __y) noexcept
290  { return !(__y < __x); }
291
292  inline bool
293  operator>(thread::id __x, thread::id __y) noexcept
294  { return __y < __x; }
295
296  inline bool
297  operator>=(thread::id __x, thread::id __y) noexcept
298  { return !(__x < __y); }
299
300  // DR 889.
301  /// std::hash specialization for thread::id.
302  template<>
303    struct hash<thread::id>
304    : public __hash_base<size_t, thread::id>
305    {
306      size_t
307      operator()(const thread::id& __id) const noexcept
308      { return std::_Hash_impl::hash(__id._M_thread); }
309    };
310
311  template<class _CharT, class _Traits>
312    inline basic_ostream<_CharT, _Traits>&
313    operator<<(basic_ostream<_CharT, _Traits>& __out, thread::id __id)
314    {
315      if (__id == thread::id())
316	return __out << "thread::id of a non-executing thread";
317      else
318	return __out << __id._M_thread;
319    }
320
321  /** @namespace std::this_thread
322   *  @brief ISO C++ 2011 entities sub-namespace for thread.
323   *  30.3.2 Namespace this_thread.
324   */
325  namespace this_thread
326  {
327    /// get_id
328    inline thread::id
329    get_id() noexcept
330    {
331#ifdef __GLIBC__
332      // For the GNU C library pthread_self() is usable without linking to
333      // libpthread.so but returns 0, so we cannot use it in single-threaded
334      // programs, because this_thread::get_id() != thread::id{} must be true.
335      // We know that pthread_t is an integral type in the GNU C library.
336      if (!__gthread_active_p())
337	return thread::id(1);
338#endif
339      return thread::id(__gthread_self());
340    }
341
342    /// yield
343    inline void
344    yield() noexcept
345    {
346#ifdef _GLIBCXX_USE_SCHED_YIELD
347      __gthread_yield();
348#endif
349    }
350
351    void
352    __sleep_for(chrono::seconds, chrono::nanoseconds);
353
354    /// sleep_for
355    template<typename _Rep, typename _Period>
356      inline void
357      sleep_for(const chrono::duration<_Rep, _Period>& __rtime)
358      {
359	if (__rtime <= __rtime.zero())
360	  return;
361	auto __s = chrono::duration_cast<chrono::seconds>(__rtime);
362	auto __ns = chrono::duration_cast<chrono::nanoseconds>(__rtime - __s);
363#ifdef _GLIBCXX_USE_NANOSLEEP
364	__gthread_time_t __ts =
365	  {
366	    static_cast<std::time_t>(__s.count()),
367	    static_cast<long>(__ns.count())
368	  };
369	while (::nanosleep(&__ts, &__ts) == -1 && errno == EINTR)
370	  { }
371#else
372	__sleep_for(__s, __ns);
373#endif
374      }
375
376    /// sleep_until
377    template<typename _Clock, typename _Duration>
378      inline void
379      sleep_until(const chrono::time_point<_Clock, _Duration>& __atime)
380      {
381	auto __now = _Clock::now();
382	if (_Clock::is_steady)
383	  {
384	    if (__now < __atime)
385	      sleep_for(__atime - __now);
386	    return;
387	  }
388	while (__now < __atime)
389	  {
390	    sleep_for(__atime - __now);
391	    __now = _Clock::now();
392	  }
393      }
394  }
395
396  // @} group threads
397
398_GLIBCXX_END_NAMESPACE_VERSION
399} // namespace
400
401#endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1
402
403#endif // C++11
404
405#endif // _GLIBCXX_THREAD
406