| // <shared_mutex> -*- C++ -*- |
| |
| // Copyright (C) 2013-2014 Free Software Foundation, Inc. |
| // |
| // This file is part of the GNU ISO C++ Library. This library is free |
| // software; you can redistribute it and/or modify it under the |
| // terms of the GNU General Public License as published by the |
| // Free Software Foundation; either version 3, or (at your option) |
| // any later version. |
| |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| |
| // Under Section 7 of GPL version 3, you are granted additional |
| // permissions described in the GCC Runtime Library Exception, version |
| // 3.1, as published by the Free Software Foundation. |
| |
| // You should have received a copy of the GNU General Public License and |
| // a copy of the GCC Runtime Library Exception along with this program; |
| // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see |
| // <http://www.gnu.org/licenses/>. |
| |
| /** @file include/shared_mutex |
| * This is a Standard C++ Library header. |
| */ |
| |
| #ifndef _GLIBCXX_SHARED_MUTEX |
| #define _GLIBCXX_SHARED_MUTEX 1 |
| |
| #pragma GCC system_header |
| |
| #if __cplusplus <= 201103L |
| # include <bits/c++14_warning.h> |
| #else |
| |
| #include <bits/c++config.h> |
| #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) |
| # include <mutex> |
| # include <condition_variable> |
| #endif |
| #include <bits/functexcept.h> |
| |
| namespace std _GLIBCXX_VISIBILITY(default) |
| { |
| _GLIBCXX_BEGIN_NAMESPACE_VERSION |
| |
| /** |
| * @ingroup mutexes |
| * @{ |
| */ |
| |
| #if defined(_GLIBCXX_HAS_GTHREADS) && defined(_GLIBCXX_USE_C99_STDINT_TR1) |
| /// shared_timed_mutex |
| class shared_timed_mutex |
| { |
| #if _GTHREAD_USE_MUTEX_TIMEDLOCK |
| struct _Mutex : mutex, __timed_mutex_impl<_Mutex> |
| { |
| template<typename _Rep, typename _Period> |
| bool |
| try_lock_for(const chrono::duration<_Rep, _Period>& __rtime) |
| { return _M_try_lock_for(__rtime); } |
| |
| template<typename _Clock, typename _Duration> |
| bool |
| try_lock_until(const chrono::time_point<_Clock, _Duration>& __atime) |
| { return _M_try_lock_until(__atime); } |
| }; |
| #else |
| typedef mutex _Mutex; |
| #endif |
| |
| // Based on Howard Hinnant's reference implementation from N2406 |
| |
| _Mutex _M_mut; |
| condition_variable _M_gate1; |
| condition_variable _M_gate2; |
| unsigned _M_state; |
| |
| static constexpr unsigned _S_write_entered |
| = 1U << (sizeof(unsigned)*__CHAR_BIT__ - 1); |
| static constexpr unsigned _M_n_readers = ~_S_write_entered; |
| |
| public: |
| shared_timed_mutex() : _M_state(0) {} |
| |
| ~shared_timed_mutex() |
| { |
| _GLIBCXX_DEBUG_ASSERT( _M_state == 0 ); |
| } |
| |
| shared_timed_mutex(const shared_timed_mutex&) = delete; |
| shared_timed_mutex& operator=(const shared_timed_mutex&) = delete; |
| |
| // Exclusive ownership |
| |
| void |
| lock() |
| { |
| unique_lock<mutex> __lk(_M_mut); |
| while (_M_state & _S_write_entered) |
| _M_gate1.wait(__lk); |
| _M_state |= _S_write_entered; |
| while (_M_state & _M_n_readers) |
| _M_gate2.wait(__lk); |
| } |
| |
| bool |
| try_lock() |
| { |
| unique_lock<mutex> __lk(_M_mut, try_to_lock); |
| if (__lk.owns_lock() && _M_state == 0) |
| { |
| _M_state = _S_write_entered; |
| return true; |
| } |
| return false; |
| } |
| |
| #if _GTHREAD_USE_MUTEX_TIMEDLOCK |
| template<typename _Rep, typename _Period> |
| bool |
| try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time) |
| { |
| unique_lock<_Mutex> __lk(_M_mut, __rel_time); |
| if (__lk.owns_lock() && _M_state == 0) |
| { |
| _M_state = _S_write_entered; |
| return true; |
| } |
| return false; |
| } |
| |
| template<typename _Clock, typename _Duration> |
| bool |
| try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time) |
| { |
| unique_lock<_Mutex> __lk(_M_mut, __abs_time); |
| if (__lk.owns_lock() && _M_state == 0) |
| { |
| _M_state = _S_write_entered; |
| return true; |
| } |
| return false; |
| } |
| #endif |
| |
| void |
| unlock() |
| { |
| { |
| lock_guard<_Mutex> __lk(_M_mut); |
| _M_state = 0; |
| } |
| _M_gate1.notify_all(); |
| } |
| |
| // Shared ownership |
| |
| void |
| lock_shared() |
| { |
| unique_lock<mutex> __lk(_M_mut); |
| while ((_M_state & _S_write_entered) |
| || (_M_state & _M_n_readers) == _M_n_readers) |
| { |
| _M_gate1.wait(__lk); |
| } |
| unsigned __num_readers = (_M_state & _M_n_readers) + 1; |
| _M_state &= ~_M_n_readers; |
| _M_state |= __num_readers; |
| } |
| |
| bool |
| try_lock_shared() |
| { |
| unique_lock<_Mutex> __lk(_M_mut, try_to_lock); |
| unsigned __num_readers = _M_state & _M_n_readers; |
| if (__lk.owns_lock() && !(_M_state & _S_write_entered) |
| && __num_readers != _M_n_readers) |
| { |
| ++__num_readers; |
| _M_state &= ~_M_n_readers; |
| _M_state |= __num_readers; |
| return true; |
| } |
| return false; |
| } |
| |
| #if _GTHREAD_USE_MUTEX_TIMEDLOCK |
| template<typename _Rep, typename _Period> |
| bool |
| try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time) |
| { |
| unique_lock<_Mutex> __lk(_M_mut, __rel_time); |
| if (__lk.owns_lock()) |
| { |
| unsigned __num_readers = _M_state & _M_n_readers; |
| if (!(_M_state & _S_write_entered) |
| && __num_readers != _M_n_readers) |
| { |
| ++__num_readers; |
| _M_state &= ~_M_n_readers; |
| _M_state |= __num_readers; |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| template <typename _Clock, typename _Duration> |
| bool |
| try_lock_shared_until(const chrono::time_point<_Clock, |
| _Duration>& __abs_time) |
| { |
| unique_lock<_Mutex> __lk(_M_mut, __abs_time); |
| if (__lk.owns_lock()) |
| { |
| unsigned __num_readers = _M_state & _M_n_readers; |
| if (!(_M_state & _S_write_entered) |
| && __num_readers != _M_n_readers) |
| { |
| ++__num_readers; |
| _M_state &= ~_M_n_readers; |
| _M_state |= __num_readers; |
| return true; |
| } |
| } |
| return false; |
| } |
| #endif |
| |
| void |
| unlock_shared() |
| { |
| lock_guard<_Mutex> __lk(_M_mut); |
| unsigned __num_readers = (_M_state & _M_n_readers) - 1; |
| _M_state &= ~_M_n_readers; |
| _M_state |= __num_readers; |
| if (_M_state & _S_write_entered) |
| { |
| if (__num_readers == 0) |
| _M_gate2.notify_one(); |
| } |
| else |
| { |
| if (__num_readers == _M_n_readers - 1) |
| _M_gate1.notify_one(); |
| } |
| } |
| }; |
| #endif // _GLIBCXX_HAS_GTHREADS && _GLIBCXX_USE_C99_STDINT_TR1 |
| |
| /// shared_lock |
| template<typename _Mutex> |
| class shared_lock |
| { |
| public: |
| typedef _Mutex mutex_type; |
| |
| // Shared locking |
| |
| shared_lock() noexcept : _M_pm(nullptr), _M_owns(false) { } |
| |
| explicit |
| shared_lock(mutex_type& __m) : _M_pm(&__m), _M_owns(true) |
| { __m.lock_shared(); } |
| |
| shared_lock(mutex_type& __m, defer_lock_t) noexcept |
| : _M_pm(&__m), _M_owns(false) { } |
| |
| shared_lock(mutex_type& __m, try_to_lock_t) |
| : _M_pm(&__m), _M_owns(__m.try_lock_shared()) { } |
| |
| shared_lock(mutex_type& __m, adopt_lock_t) |
| : _M_pm(&__m), _M_owns(true) { } |
| |
| template<typename _Clock, typename _Duration> |
| shared_lock(mutex_type& __m, |
| const chrono::time_point<_Clock, _Duration>& __abs_time) |
| : _M_pm(&__m), _M_owns(__m.try_lock_shared_until(__abs_time)) { } |
| |
| template<typename _Rep, typename _Period> |
| shared_lock(mutex_type& __m, |
| const chrono::duration<_Rep, _Period>& __rel_time) |
| : _M_pm(&__m), _M_owns(__m.try_lock_shared_for(__rel_time)) { } |
| |
| ~shared_lock() |
| { |
| if (_M_owns) |
| _M_pm->unlock_shared(); |
| } |
| |
| shared_lock(shared_lock const&) = delete; |
| shared_lock& operator=(shared_lock const&) = delete; |
| |
| shared_lock(shared_lock&& __sl) noexcept : shared_lock() |
| { swap(__sl); } |
| |
| shared_lock& |
| operator=(shared_lock&& __sl) noexcept |
| { |
| shared_lock(std::move(__sl)).swap(*this); |
| return *this; |
| } |
| |
| void |
| lock() |
| { |
| _M_lockable(); |
| _M_pm->lock_shared(); |
| _M_owns = true; |
| } |
| |
| bool |
| try_lock() |
| { |
| _M_lockable(); |
| return _M_owns = _M_pm->try_lock_shared(); |
| } |
| |
| template<typename _Rep, typename _Period> |
| bool |
| try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time) |
| { |
| _M_lockable(); |
| return _M_owns = _M_pm->try_lock_shared_for(__rel_time); |
| } |
| |
| template<typename _Clock, typename _Duration> |
| bool |
| try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time) |
| { |
| _M_lockable(); |
| return _M_owns = _M_pm->try_lock_shared_until(__abs_time); |
| } |
| |
| void |
| unlock() |
| { |
| if (!_M_owns) |
| __throw_system_error(int(errc::resource_deadlock_would_occur)); |
| _M_pm->unlock_shared(); |
| _M_owns = false; |
| } |
| |
| // Setters |
| |
| void |
| swap(shared_lock& __u) noexcept |
| { |
| std::swap(_M_pm, __u._M_pm); |
| std::swap(_M_owns, __u._M_owns); |
| } |
| |
| mutex_type* |
| release() noexcept |
| { |
| _M_owns = false; |
| return std::exchange(_M_pm, nullptr); |
| } |
| |
| // Getters |
| |
| bool owns_lock() const noexcept { return _M_owns; } |
| |
| explicit operator bool() const noexcept { return _M_owns; } |
| |
| mutex_type* mutex() const noexcept { return _M_pm; } |
| |
| private: |
| void |
| _M_lockable() const |
| { |
| if (_M_pm == nullptr) |
| __throw_system_error(int(errc::operation_not_permitted)); |
| if (_M_owns) |
| __throw_system_error(int(errc::resource_deadlock_would_occur)); |
| } |
| |
| mutex_type* _M_pm; |
| bool _M_owns; |
| }; |
| |
| /// Swap specialization for shared_lock |
| template<typename _Mutex> |
| void |
| swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) noexcept |
| { __x.swap(__y); } |
| |
| // @} group mutexes |
| _GLIBCXX_END_NAMESPACE_VERSION |
| } // namespace |
| |
| #endif // C++14 |
| |
| #endif // _GLIBCXX_SHARED_MUTEX |