1*5ffd83dbSDimitry Andric// -*- C++ -*- 2*5ffd83dbSDimitry Andric//===--------------------------- latch -----------------------------------===// 3*5ffd83dbSDimitry Andric// 4*5ffd83dbSDimitry Andric// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5*5ffd83dbSDimitry Andric// See https://llvm.org/LICENSE.txt for license information. 6*5ffd83dbSDimitry Andric// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7*5ffd83dbSDimitry Andric// 8*5ffd83dbSDimitry Andric//===----------------------------------------------------------------------===// 9*5ffd83dbSDimitry Andric 10*5ffd83dbSDimitry Andric#ifndef _LIBCPP_LATCH 11*5ffd83dbSDimitry Andric#define _LIBCPP_LATCH 12*5ffd83dbSDimitry Andric 13*5ffd83dbSDimitry Andric/* 14*5ffd83dbSDimitry Andric latch synopsis 15*5ffd83dbSDimitry Andric 16*5ffd83dbSDimitry Andricnamespace std 17*5ffd83dbSDimitry Andric{ 18*5ffd83dbSDimitry Andric 19*5ffd83dbSDimitry Andric class latch 20*5ffd83dbSDimitry Andric { 21*5ffd83dbSDimitry Andric public: 22*5ffd83dbSDimitry Andric constexpr explicit latch(ptrdiff_t __expected); 23*5ffd83dbSDimitry Andric ~latch(); 24*5ffd83dbSDimitry Andric 25*5ffd83dbSDimitry Andric latch(const latch&) = delete; 26*5ffd83dbSDimitry Andric latch& operator=(const latch&) = delete; 27*5ffd83dbSDimitry Andric 28*5ffd83dbSDimitry Andric void count_down(ptrdiff_t __update = 1); 29*5ffd83dbSDimitry Andric bool try_wait() const noexcept; 30*5ffd83dbSDimitry Andric void wait() const; 31*5ffd83dbSDimitry Andric void arrive_and_wait(ptrdiff_t __update = 1); 32*5ffd83dbSDimitry Andric 33*5ffd83dbSDimitry Andric private: 34*5ffd83dbSDimitry Andric ptrdiff_t __counter; // exposition only 35*5ffd83dbSDimitry Andric }; 36*5ffd83dbSDimitry Andric 37*5ffd83dbSDimitry Andric} 38*5ffd83dbSDimitry Andric 39*5ffd83dbSDimitry Andric*/ 40*5ffd83dbSDimitry Andric 41*5ffd83dbSDimitry Andric#include <__config> 42*5ffd83dbSDimitry Andric#include <atomic> 43*5ffd83dbSDimitry Andric 44*5ffd83dbSDimitry Andric#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 45*5ffd83dbSDimitry Andric#pragma GCC system_header 46*5ffd83dbSDimitry Andric#endif 47*5ffd83dbSDimitry Andric 48*5ffd83dbSDimitry Andric#ifdef _LIBCPP_HAS_NO_THREADS 49*5ffd83dbSDimitry Andric# error <latch> is not supported on this single threaded system 50*5ffd83dbSDimitry Andric#endif 51*5ffd83dbSDimitry Andric 52*5ffd83dbSDimitry Andric#if _LIBCPP_STD_VER >= 14 53*5ffd83dbSDimitry Andric 54*5ffd83dbSDimitry Andric_LIBCPP_BEGIN_NAMESPACE_STD 55*5ffd83dbSDimitry Andric 56*5ffd83dbSDimitry Andricclass latch 57*5ffd83dbSDimitry Andric{ 58*5ffd83dbSDimitry Andric __atomic_base<ptrdiff_t> __a; 59*5ffd83dbSDimitry Andric 60*5ffd83dbSDimitry Andricpublic: 61*5ffd83dbSDimitry Andric static constexpr ptrdiff_t max() noexcept { 62*5ffd83dbSDimitry Andric return numeric_limits<ptrdiff_t>::max(); 63*5ffd83dbSDimitry Andric } 64*5ffd83dbSDimitry Andric 65*5ffd83dbSDimitry Andric inline _LIBCPP_INLINE_VISIBILITY 66*5ffd83dbSDimitry Andric constexpr explicit latch(ptrdiff_t __expected) : __a(__expected) { } 67*5ffd83dbSDimitry Andric 68*5ffd83dbSDimitry Andric ~latch() = default; 69*5ffd83dbSDimitry Andric latch(const latch&) = delete; 70*5ffd83dbSDimitry Andric latch& operator=(const latch&) = delete; 71*5ffd83dbSDimitry Andric 72*5ffd83dbSDimitry Andric inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY 73*5ffd83dbSDimitry Andric void count_down(ptrdiff_t __update = 1) 74*5ffd83dbSDimitry Andric { 75*5ffd83dbSDimitry Andric auto const __old = __a.fetch_sub(__update, memory_order_release); 76*5ffd83dbSDimitry Andric if(__old == __update) 77*5ffd83dbSDimitry Andric __a.notify_all(); 78*5ffd83dbSDimitry Andric } 79*5ffd83dbSDimitry Andric inline _LIBCPP_INLINE_VISIBILITY 80*5ffd83dbSDimitry Andric bool try_wait() const noexcept 81*5ffd83dbSDimitry Andric { 82*5ffd83dbSDimitry Andric return 0 == __a.load(memory_order_acquire); 83*5ffd83dbSDimitry Andric } 84*5ffd83dbSDimitry Andric inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY 85*5ffd83dbSDimitry Andric void wait() const 86*5ffd83dbSDimitry Andric { 87*5ffd83dbSDimitry Andric auto const __test_fn = [=]() -> bool { 88*5ffd83dbSDimitry Andric return try_wait(); 89*5ffd83dbSDimitry Andric }; 90*5ffd83dbSDimitry Andric __cxx_atomic_wait(&__a.__a_, __test_fn); 91*5ffd83dbSDimitry Andric } 92*5ffd83dbSDimitry Andric inline _LIBCPP_AVAILABILITY_SYNC _LIBCPP_INLINE_VISIBILITY 93*5ffd83dbSDimitry Andric void arrive_and_wait(ptrdiff_t __update = 1) 94*5ffd83dbSDimitry Andric { 95*5ffd83dbSDimitry Andric count_down(__update); 96*5ffd83dbSDimitry Andric wait(); 97*5ffd83dbSDimitry Andric } 98*5ffd83dbSDimitry Andric}; 99*5ffd83dbSDimitry Andric 100*5ffd83dbSDimitry Andric_LIBCPP_END_NAMESPACE_STD 101*5ffd83dbSDimitry Andric 102*5ffd83dbSDimitry Andric#endif // _LIBCPP_STD_VER >= 14 103*5ffd83dbSDimitry Andric 104*5ffd83dbSDimitry Andric#endif //_LIBCPP_LATCH 105