libcxx/include/__thread/this_thread.h

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 #ifndef _LIBCPP___THREAD_THIS_THREAD_H
  11 #define _LIBCPP___THREAD_THIS_THREAD_H
  12
  13 #include <__chrono/steady_clock.h>
  14 #include <__chrono/time_point.h>
  15 #include <__condition_variable/condition_variable.h>
  16 #include <__config>
  17 #include <__mutex/mutex.h>
  18 #include <__mutex/unique_lock.h>
  19 #include <__threading_support>
  20
  21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  22 #  pragma GCC system_header
  23 #endif
  24
  25 _LIBCPP_PUSH_MACROS
  26 #include <__undef_macros>
  27
  28 _LIBCPP_BEGIN_NAMESPACE_STD
  29
  30 namespace this_thread
  31 {
  32
  33 _LIBCPP_EXPORTED_FROM_ABI void sleep_for(const chrono::nanoseconds& __ns);
  34
  35 template <class _Rep, class _Period>
  36 _LIBCPP_HIDE_FROM_ABI void
  37 sleep_for(const chrono::duration<_Rep, _Period>& __d)
  38 {
  39     if (__d > chrono::duration<_Rep, _Period>::zero())
  40     {
  41         // The standard guarantees a 64bit signed integer resolution for nanoseconds,
  42         // so use INT64_MAX / 1e9 as cut-off point. Use a constant to avoid <climits>
  43         // and issues with long double folding on PowerPC with GCC.
  44         _LIBCPP_CONSTEXPR chrono::duration<long double> __max =
  45             chrono::duration<long double>(9223372036.0L);
  46         chrono::nanoseconds __ns;
  47         if (__d < __max)
  48         {
  49             __ns = chrono::duration_cast<chrono::nanoseconds>(__d);
  50             if (__ns < __d)
  51                 ++__ns;
  52         }
  53         else
  54             __ns = chrono::nanoseconds::max();
  55         this_thread::sleep_for(__ns);
  56     }
  57 }
  58
  59 template <class _Clock, class _Duration>
  60 _LIBCPP_HIDE_FROM_ABI void
  61 sleep_until(const chrono::time_point<_Clock, _Duration>& __t)
  62 {
  63     mutex __mut;
  64     condition_variable __cv;
  65     unique_lock<mutex> __lk(__mut);
  66     while (_Clock::now() < __t)
  67         __cv.wait_until(__lk, __t);
  68 }
  69
  70 template <class _Duration>
  71 inline _LIBCPP_INLINE_VISIBILITY
  72 void
  73 sleep_until(const chrono::time_point<chrono::steady_clock, _Duration>& __t)
  74 {
  75     this_thread::sleep_for(__t - chrono::steady_clock::now());
  76 }
  77
  78 inline _LIBCPP_INLINE_VISIBILITY
  79 void yield() _NOEXCEPT {__libcpp_thread_yield();}
  80
  81 } // namespace this_thread
  82
  83 _LIBCPP_END_NAMESPACE_STD
  84
  85 _LIBCPP_POP_MACROS
  86
  87 #endif // _LIBCPP___THREAD_THIS_THREAD_H