Warning, /include/c++/v1/__cxx03/semaphore is written in an unsupported language. File is not indexed.
0001 // -*- C++ -*-
0002 //===----------------------------------------------------------------------===//
0003 //
0004 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
0005 // See https://llvm.org/LICENSE.txt for license information.
0006 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
0007 //
0008 //===----------------------------------------------------------------------===//
0009
0010 #ifndef _LIBCPP___CXX03_SEMAPHORE
0011 #define _LIBCPP___CXX03_SEMAPHORE
0012
0013 /*
0014 semaphore synopsis
0015
0016 namespace std {
0017
0018 template<ptrdiff_t least_max_value = implementation-defined>
0019 class counting_semaphore
0020 {
0021 public:
0022 static constexpr ptrdiff_t max() noexcept;
0023
0024 constexpr explicit counting_semaphore(ptrdiff_t desired);
0025 ~counting_semaphore();
0026
0027 counting_semaphore(const counting_semaphore&) = delete;
0028 counting_semaphore& operator=(const counting_semaphore&) = delete;
0029
0030 void release(ptrdiff_t update = 1);
0031 void acquire();
0032 bool try_acquire() noexcept;
0033 template<class Rep, class Period>
0034 bool try_acquire_for(const chrono::duration<Rep, Period>& rel_time);
0035 template<class Clock, class Duration>
0036 bool try_acquire_until(const chrono::time_point<Clock, Duration>& abs_time);
0037
0038 private:
0039 ptrdiff_t counter; // exposition only
0040 };
0041
0042 using binary_semaphore = counting_semaphore<1>;
0043
0044 }
0045
0046 */
0047
0048 #include <__cxx03/__config>
0049
0050 #if !defined(_LIBCPP_HAS_NO_THREADS)
0051
0052 # include <__cxx03/__assert>
0053 # include <__cxx03/__atomic/atomic_base.h>
0054 # include <__cxx03/__atomic/atomic_sync.h>
0055 # include <__cxx03/__atomic/memory_order.h>
0056 # include <__cxx03/__chrono/time_point.h>
0057 # include <__cxx03/__thread/poll_with_backoff.h>
0058 # include <__cxx03/__thread/support.h>
0059 # include <__cxx03/__thread/timed_backoff_policy.h>
0060 # include <__cxx03/cstddef>
0061 # include <__cxx03/limits>
0062 # include <__cxx03/version>
0063
0064 # if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
0065 # pragma GCC system_header
0066 # endif
0067
0068 _LIBCPP_PUSH_MACROS
0069 # include <__cxx03/__undef_macros>
0070
0071 # if _LIBCPP_STD_VER >= 14
0072
0073 _LIBCPP_BEGIN_NAMESPACE_STD
0074
0075 /*
0076
0077 __atomic_semaphore_base is the general-case implementation.
0078 It is a typical Dijkstra semaphore algorithm over atomics, wait and notify
0079 functions. It avoids contention against users' own use of those facilities.
0080
0081 */
0082
0083 # define _LIBCPP_SEMAPHORE_MAX (numeric_limits<ptrdiff_t>::max())
0084
0085 class __atomic_semaphore_base {
0086 __atomic_base<ptrdiff_t> __a_;
0087
0088 public:
0089 _LIBCPP_HIDE_FROM_ABI constexpr explicit __atomic_semaphore_base(ptrdiff_t __count) : __a_(__count) {}
0090 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void release(ptrdiff_t __update = 1) {
0091 auto __old = __a_.fetch_add(__update, memory_order_release);
0092 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
0093 __update <= _LIBCPP_SEMAPHORE_MAX - __old, "update is greater than the expected value");
0094 if (__old == 0) {
0095 __a_.notify_all();
0096 }
0097 }
0098 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void acquire() {
0099 std::__atomic_wait_unless(
0100 __a_, [this](ptrdiff_t& __old) { return __try_acquire_impl(__old); }, memory_order_relaxed);
0101 }
0102 template <class _Rep, class _Period>
0103 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool
0104 try_acquire_for(chrono::duration<_Rep, _Period> const& __rel_time) {
0105 if (__rel_time == chrono::duration<_Rep, _Period>::zero())
0106 return try_acquire();
0107 auto const __poll_fn = [this]() { return try_acquire(); };
0108 return std::__libcpp_thread_poll_with_backoff(__poll_fn, __libcpp_timed_backoff_policy(), __rel_time);
0109 }
0110 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool try_acquire() {
0111 auto __old = __a_.load(memory_order_relaxed);
0112 return __try_acquire_impl(__old);
0113 }
0114
0115 private:
0116 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool __try_acquire_impl(ptrdiff_t& __old) {
0117 while (true) {
0118 if (__old == 0)
0119 return false;
0120 if (__a_.compare_exchange_weak(__old, __old - 1, memory_order_acquire, memory_order_relaxed))
0121 return true;
0122 }
0123 }
0124 };
0125
0126 template <ptrdiff_t __least_max_value = _LIBCPP_SEMAPHORE_MAX>
0127 class _LIBCPP_DEPRECATED_ATOMIC_SYNC counting_semaphore {
0128 __atomic_semaphore_base __semaphore_;
0129
0130 public:
0131 static_assert(__least_max_value >= 0, "The least maximum value must be a positive number");
0132
0133 static constexpr ptrdiff_t max() noexcept { return __least_max_value; }
0134
0135 _LIBCPP_HIDE_FROM_ABI constexpr explicit counting_semaphore(ptrdiff_t __count) : __semaphore_(__count) {
0136 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
0137 __count >= 0,
0138 "counting_semaphore::counting_semaphore(ptrdiff_t): counting_semaphore cannot be "
0139 "initialized with a negative value");
0140 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(
0141 __count <= max(),
0142 "counting_semaphore::counting_semaphore(ptrdiff_t): counting_semaphore cannot be "
0143 "initialized with a value greater than max()");
0144 }
0145 ~counting_semaphore() = default;
0146
0147 counting_semaphore(const counting_semaphore&) = delete;
0148 counting_semaphore& operator=(const counting_semaphore&) = delete;
0149
0150 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void release(ptrdiff_t __update = 1) {
0151 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN(__update >= 0, "counting_semaphore:release called with a negative value");
0152 __semaphore_.release(__update);
0153 }
0154 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI void acquire() { __semaphore_.acquire(); }
0155 template <class _Rep, class _Period>
0156 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool
0157 try_acquire_for(chrono::duration<_Rep, _Period> const& __rel_time) {
0158 return __semaphore_.try_acquire_for(chrono::duration_cast<chrono::nanoseconds>(__rel_time));
0159 }
0160 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool try_acquire() { return __semaphore_.try_acquire(); }
0161 template <class _Clock, class _Duration>
0162 _LIBCPP_AVAILABILITY_SYNC _LIBCPP_HIDE_FROM_ABI bool
0163 try_acquire_until(chrono::time_point<_Clock, _Duration> const& __abs_time) {
0164 auto const __current = _Clock::now();
0165 if (__current >= __abs_time)
0166 return try_acquire();
0167 else
0168 return try_acquire_for(__abs_time - __current);
0169 }
0170 };
0171
0172 _LIBCPP_SUPPRESS_DEPRECATED_PUSH
0173 using binary_semaphore _LIBCPP_DEPRECATED_ATOMIC_SYNC = counting_semaphore<1>;
0174 _LIBCPP_SUPPRESS_DEPRECATED_POP
0175
0176 _LIBCPP_END_NAMESPACE_STD
0177
0178 # endif // _LIBCPP_STD_VER >= 14
0179
0180 _LIBCPP_POP_MACROS
0181
0182 #endif // !defined(_LIBCPP_HAS_NO_THREADS)
0183
0184 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
0185 # include <__cxx03/atomic>
0186 #endif
0187
0188 #endif //_LIBCPP___CXX03_SEMAPHORE
