N3659: Shared locking in C++ Revision 2, c++1y only
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@191127 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Howard Hinnant
419
include/shared_mutex
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419
include/shared_mutex
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// -*- C++ -*-
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//===------------------------ shared_mutex --------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP_SHARED_MUTEX
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#define _LIBCPP_SHARED_MUTEX
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/*
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shared_mutex synopsis
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// C++1y
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namespace std
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{
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class shared_mutex
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{
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public:
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shared_mutex();
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~shared_mutex();
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shared_mutex(const shared_mutex&) = delete;
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shared_mutex& operator=(const shared_mutex&) = delete;
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// Exclusive ownership
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void lock(); // blocking
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bool try_lock();
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template <class Rep, class Period>
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bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
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template <class Clock, class Duration>
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bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
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void unlock();
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// Shared ownership
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void lock_shared(); // blocking
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bool try_lock_shared();
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template <class Rep, class Period>
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bool
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try_lock_shared_for(const chrono::duration<Rep, Period>& rel_time);
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template <class Clock, class Duration>
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bool
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try_lock_shared_until(const chrono::time_point<Clock, Duration>& abs_time);
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void unlock_shared();
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};
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template <class Mutex>
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class shared_lock
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{
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public:
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typedef Mutex mutex_type;
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// Shared locking
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shared_lock() noexcept;
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explicit shared_lock(mutex_type& m); // blocking
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shared_lock(mutex_type& m, defer_lock_t) noexcept;
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shared_lock(mutex_type& m, try_to_lock_t);
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shared_lock(mutex_type& m, adopt_lock_t);
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template <class Clock, class Duration>
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shared_lock(mutex_type& m,
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const chrono::time_point<Clock, Duration>& abs_time);
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template <class Rep, class Period>
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shared_lock(mutex_type& m,
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const chrono::duration<Rep, Period>& rel_time);
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~shared_lock();
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shared_lock(shared_lock const&) = delete;
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shared_lock& operator=(shared_lock const&) = delete;
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shared_lock(shared_lock&& u) noexcept;
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shared_lock& operator=(shared_lock&& u) noexcept;
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void lock(); // blocking
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bool try_lock();
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template <class Rep, class Period>
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bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
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template <class Clock, class Duration>
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bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
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void unlock();
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// Setters
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void swap(shared_lock& u) noexcept;
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mutex_type* release() noexcept;
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// Getters
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bool owns_lock() const noexcept;
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explicit operator bool () const noexcept;
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mutex_type* mutex() const noexcept;
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};
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template <class Mutex>
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void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
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} // std
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*/
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#include <__config>
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#if _LIBCPP_STD_VER > 11 || defined(_LIBCPP_BUILDING_SHARED_MUTEX)
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#include <__mutex_base>
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#include <__undef_min_max>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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#pragma GCC system_header
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#endif
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_LIBCPP_BEGIN_NAMESPACE_STD
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class _LIBCPP_TYPE_VIS shared_mutex
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{
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mutex __mut_;
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condition_variable __gate1_;
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condition_variable __gate2_;
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unsigned __state_;
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static const unsigned __write_entered_ = 1U << (sizeof(unsigned)*__CHAR_BIT__ - 1);
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static const unsigned __n_readers_ = ~__write_entered_;
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public:
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shared_mutex();
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_LIBCPP_INLINE_VISIBILITY ~shared_mutex() = default;
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shared_mutex(const shared_mutex&) = delete;
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shared_mutex& operator=(const shared_mutex&) = delete;
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// Exclusive ownership
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void lock();
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bool try_lock();
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template <class _Rep, class _Period>
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_LIBCPP_INLINE_VISIBILITY
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bool
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try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
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{
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return try_lock_until(chrono::steady_clock::now() + __rel_time);
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}
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template <class _Clock, class _Duration>
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bool
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try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
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void unlock();
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// Shared ownership
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void lock_shared();
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bool try_lock_shared();
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template <class _Rep, class _Period>
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_LIBCPP_INLINE_VISIBILITY
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bool
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try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
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{
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return try_lock_shared_until(chrono::steady_clock::now() + __rel_time);
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}
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template <class _Clock, class _Duration>
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bool
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try_lock_shared_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
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void unlock_shared();
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};
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template <class _Clock, class _Duration>
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bool
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shared_mutex::try_lock_until(
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const chrono::time_point<_Clock, _Duration>& __abs_time)
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{
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unique_lock<mutex> __lk(__mut_);
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if (__state_ & __write_entered_)
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{
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while (true)
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{
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cv_status __status = __gate1_.wait_until(__lk, __abs_time);
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if ((__state_ & __write_entered_) == 0)
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break;
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if (__status == cv_status::timeout)
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return false;
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}
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}
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__state_ |= __write_entered_;
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if (__state_ & __n_readers_)
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{
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while (true)
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{
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cv_status __status = __gate2_.wait_until(__lk, __abs_time);
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if ((__state_ & __n_readers_) == 0)
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break;
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if (__status == cv_status::timeout)
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{
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__state_ &= ~__write_entered_;
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return false;
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}
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}
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}
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return true;
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}
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template <class _Clock, class _Duration>
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bool
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shared_mutex::try_lock_shared_until(
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const chrono::time_point<_Clock, _Duration>& __abs_time)
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{
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unique_lock<mutex> __lk(__mut_);
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if ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
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{
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while (true)
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{
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cv_status status = __gate1_.wait_until(__lk, __abs_time);
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if ((__state_ & __write_entered_) == 0 &&
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(__state_ & __n_readers_) < __n_readers_)
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break;
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if (status == cv_status::timeout)
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return false;
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}
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}
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unsigned __num_readers = (__state_ & __n_readers_) + 1;
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__state_ &= ~__n_readers_;
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__state_ |= __num_readers;
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return true;
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}
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template <class _Mutex>
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class shared_lock
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{
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public:
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typedef _Mutex mutex_type;
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private:
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mutex_type* __m_;
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bool __owns_;
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public:
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_LIBCPP_INLINE_VISIBILITY
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shared_lock() noexcept
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: __m_(nullptr),
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__owns_(false)
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{}
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_LIBCPP_INLINE_VISIBILITY
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explicit shared_lock(mutex_type& __m)
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: __m_(&__m),
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__owns_(true)
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{__m_->lock_shared();}
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_LIBCPP_INLINE_VISIBILITY
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shared_lock(mutex_type& __m, defer_lock_t) noexcept
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: __m_(&__m),
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__owns_(false)
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{}
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_LIBCPP_INLINE_VISIBILITY
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shared_lock(mutex_type& __m, try_to_lock_t)
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: __m_(&__m),
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__owns_(__m.try_lock_shared())
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{}
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_LIBCPP_INLINE_VISIBILITY
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shared_lock(mutex_type& __m, adopt_lock_t)
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: __m_(&__m),
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__owns_(true)
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{}
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template <class _Clock, class _Duration>
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_LIBCPP_INLINE_VISIBILITY
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shared_lock(mutex_type& __m,
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const chrono::time_point<_Clock, _Duration>& __abs_time)
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: __m_(&__m),
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__owns_(__m.try_lock_shared_until(__abs_time))
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{}
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template <class _Rep, class _Period>
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_LIBCPP_INLINE_VISIBILITY
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shared_lock(mutex_type& __m,
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const chrono::duration<_Rep, _Period>& __rel_time)
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: __m_(&__m),
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__owns_(__m.try_lock_shared_for(__rel_time))
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{}
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_LIBCPP_INLINE_VISIBILITY
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~shared_lock()
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{
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if (__owns_)
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__m_->unlock_shared();
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}
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shared_lock(shared_lock const&) = delete;
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shared_lock& operator=(shared_lock const&) = delete;
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_LIBCPP_INLINE_VISIBILITY
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shared_lock(shared_lock&& __u) noexcept
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: __m_(__u.__m_),
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__owns_(__u.__owns_)
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{
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__u.__m_ = nullptr;
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__u.__owns_ = false;
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}
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_LIBCPP_INLINE_VISIBILITY
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shared_lock& operator=(shared_lock&& __u) noexcept
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{
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if (__owns_)
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__m_->unlock_shared();
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__m_ = nullptr;
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__owns_ = false;
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__m_ = __u.__m_;
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__owns_ = __u.__owns_;
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__u.__m_ = nullptr;
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__u.__owns_ = false;
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return *this;
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}
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void lock();
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bool try_lock();
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template <class Rep, class Period>
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bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
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template <class Clock, class Duration>
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bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
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void unlock();
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// Setters
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_LIBCPP_INLINE_VISIBILITY
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void swap(shared_lock& __u) noexcept
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{
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_VSTD::swap(__m_, __u.__m_);
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_VSTD::swap(__owns_, __u.__owns_);
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}
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_LIBCPP_INLINE_VISIBILITY
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mutex_type* release() noexcept
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{
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mutex_type* __m = __m_;
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__m_ = nullptr;
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__owns_ = false;
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return __m;
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}
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// Getters
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_LIBCPP_INLINE_VISIBILITY
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bool owns_lock() const noexcept {return __owns_;}
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_LIBCPP_INLINE_VISIBILITY
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explicit operator bool () const noexcept {return __owns_;}
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_LIBCPP_INLINE_VISIBILITY
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mutex_type* mutex() const noexcept {return __m_;}
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};
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template <class _Mutex>
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void
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shared_lock<_Mutex>::lock()
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{
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if (__m_ == nullptr)
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__throw_system_error(EPERM, "shared_lock::lock: references null mutex");
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if (__owns_)
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__throw_system_error(EDEADLK, "shared_lock::lock: already locked");
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__m_->lock_shared();
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__owns_ = true;
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}
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template <class _Mutex>
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bool
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shared_lock<_Mutex>::try_lock()
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{
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if (__m_ == nullptr)
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__throw_system_error(EPERM, "shared_lock::try_lock: references null mutex");
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if (__owns_)
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__throw_system_error(EDEADLK, "shared_lock::try_lock: already locked");
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__owns_ = __m_->try_lock_shared();
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return __owns_;
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}
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template <class _Mutex>
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template <class _Rep, class _Period>
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bool
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shared_lock<_Mutex>::try_lock_for(const chrono::duration<_Rep, _Period>& __d)
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{
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if (__m_ == nullptr)
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__throw_system_error(EPERM, "shared_lock::try_lock_for: references null mutex");
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if (__owns_)
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__throw_system_error(EDEADLK, "shared_lock::try_lock_for: already locked");
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__owns_ = __m_->try_lock_shared_for(__d);
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return __owns_;
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}
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template <class _Mutex>
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template <class _Clock, class _Duration>
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bool
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shared_lock<_Mutex>::try_lock_until(const chrono::time_point<_Clock, _Duration>& __t)
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{
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if (__m_ == nullptr)
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__throw_system_error(EPERM, "shared_lock::try_lock_until: references null mutex");
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if (__owns_)
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__throw_system_error(EDEADLK, "shared_lock::try_lock_until: already locked");
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__owns_ = __m_->try_lock_shared_until(__t);
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return __owns_;
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}
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template <class _Mutex>
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void
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shared_lock<_Mutex>::unlock()
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{
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if (!__owns_)
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__throw_system_error(EPERM, "shared_lock::unlock: not locked");
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__m_->unlock_shared();
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__owns_ = false;
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}
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template <class _Mutex>
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inline _LIBCPP_INLINE_VISIBILITY
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void
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swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) noexcept
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{__x.swap(__y);}
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_LIBCPP_END_NAMESPACE_STD
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#endif // _LIBCPP_STD_VER > 11
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#endif // _LIBCPP_SHARED_MUTEX
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Block a user