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
diff --git a/include/shared_mutex b/include/shared_mutex
new file mode 100644
index 0000000..5b1f53a
--- /dev/null
+++ b/include/shared_mutex
@@ -0,0 +1,419 @@
+// -*- C++ -*-
+//===------------------------ shared_mutex --------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SHARED_MUTEX
+#define _LIBCPP_SHARED_MUTEX
+
+/*
+ shared_mutex synopsis
+
+// C++1y
+
+namespace std
+{
+
+class shared_mutex
+{
+public:
+ shared_mutex();
+ ~shared_mutex();
+
+ shared_mutex(const shared_mutex&) = delete;
+ shared_mutex& operator=(const shared_mutex&) = delete;
+
+ // Exclusive ownership
+ void lock(); // blocking
+ bool try_lock();
+ template <class Rep, class Period>
+ bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
+ template <class Clock, class Duration>
+ bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
+ void unlock();
+
+ // Shared ownership
+ void lock_shared(); // blocking
+ bool try_lock_shared();
+ template <class Rep, class Period>
+ bool
+ try_lock_shared_for(const chrono::duration<Rep, Period>& rel_time);
+ template <class Clock, class Duration>
+ bool
+ try_lock_shared_until(const chrono::time_point<Clock, Duration>& abs_time);
+ void unlock_shared();
+};
+
+template <class Mutex>
+class shared_lock
+{
+public:
+ typedef Mutex mutex_type;
+
+ // Shared locking
+ shared_lock() noexcept;
+ explicit shared_lock(mutex_type& m); // blocking
+ shared_lock(mutex_type& m, defer_lock_t) noexcept;
+ shared_lock(mutex_type& m, try_to_lock_t);
+ shared_lock(mutex_type& m, adopt_lock_t);
+ template <class Clock, class Duration>
+ shared_lock(mutex_type& m,
+ const chrono::time_point<Clock, Duration>& abs_time);
+ template <class Rep, class Period>
+ shared_lock(mutex_type& m,
+ const chrono::duration<Rep, Period>& rel_time);
+ ~shared_lock();
+
+ shared_lock(shared_lock const&) = delete;
+ shared_lock& operator=(shared_lock const&) = delete;
+
+ shared_lock(shared_lock&& u) noexcept;
+ shared_lock& operator=(shared_lock&& u) noexcept;
+
+ void lock(); // blocking
+ bool try_lock();
+ template <class Rep, class Period>
+ bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
+ template <class Clock, class Duration>
+ bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
+ void unlock();
+
+ // Setters
+ void swap(shared_lock& u) noexcept;
+ mutex_type* release() noexcept;
+
+ // Getters
+ bool owns_lock() const noexcept;
+ explicit operator bool () const noexcept;
+ mutex_type* mutex() const noexcept;
+};
+
+template <class Mutex>
+ void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
+
+} // std
+
+*/
+
+#include <__config>
+
+#if _LIBCPP_STD_VER > 11 || defined(_LIBCPP_BUILDING_SHARED_MUTEX)
+
+#include <__mutex_base>
+
+#include <__undef_min_max>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+class _LIBCPP_TYPE_VIS shared_mutex
+{
+ mutex __mut_;
+ condition_variable __gate1_;
+ condition_variable __gate2_;
+ unsigned __state_;
+
+ static const unsigned __write_entered_ = 1U << (sizeof(unsigned)*__CHAR_BIT__ - 1);
+ static const unsigned __n_readers_ = ~__write_entered_;
+public:
+ shared_mutex();
+ _LIBCPP_INLINE_VISIBILITY ~shared_mutex() = default;
+
+ shared_mutex(const shared_mutex&) = delete;
+ shared_mutex& operator=(const shared_mutex&) = delete;
+
+ // Exclusive ownership
+ void lock();
+ bool try_lock();
+ template <class _Rep, class _Period>
+ _LIBCPP_INLINE_VISIBILITY
+ bool
+ try_lock_for(const chrono::duration<_Rep, _Period>& __rel_time)
+ {
+ return try_lock_until(chrono::steady_clock::now() + __rel_time);
+ }
+ template <class _Clock, class _Duration>
+ bool
+ try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
+ void unlock();
+
+ // Shared ownership
+ void lock_shared();
+ bool try_lock_shared();
+ template <class _Rep, class _Period>
+ _LIBCPP_INLINE_VISIBILITY
+ bool
+ try_lock_shared_for(const chrono::duration<_Rep, _Period>& __rel_time)
+ {
+ return try_lock_shared_until(chrono::steady_clock::now() + __rel_time);
+ }
+ template <class _Clock, class _Duration>
+ bool
+ try_lock_shared_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
+ void unlock_shared();
+};
+
+template <class _Clock, class _Duration>
+bool
+shared_mutex::try_lock_until(
+ const chrono::time_point<_Clock, _Duration>& __abs_time)
+{
+ unique_lock<mutex> __lk(__mut_);
+ if (__state_ & __write_entered_)
+ {
+ while (true)
+ {
+ cv_status __status = __gate1_.wait_until(__lk, __abs_time);
+ if ((__state_ & __write_entered_) == 0)
+ break;
+ if (__status == cv_status::timeout)
+ return false;
+ }
+ }
+ __state_ |= __write_entered_;
+ if (__state_ & __n_readers_)
+ {
+ while (true)
+ {
+ cv_status __status = __gate2_.wait_until(__lk, __abs_time);
+ if ((__state_ & __n_readers_) == 0)
+ break;
+ if (__status == cv_status::timeout)
+ {
+ __state_ &= ~__write_entered_;
+ return false;
+ }
+ }
+ }
+ return true;
+}
+
+template <class _Clock, class _Duration>
+bool
+shared_mutex::try_lock_shared_until(
+ const chrono::time_point<_Clock, _Duration>& __abs_time)
+{
+ unique_lock<mutex> __lk(__mut_);
+ if ((__state_ & __write_entered_) || (__state_ & __n_readers_) == __n_readers_)
+ {
+ while (true)
+ {
+ cv_status status = __gate1_.wait_until(__lk, __abs_time);
+ if ((__state_ & __write_entered_) == 0 &&
+ (__state_ & __n_readers_) < __n_readers_)
+ break;
+ if (status == cv_status::timeout)
+ return false;
+ }
+ }
+ unsigned __num_readers = (__state_ & __n_readers_) + 1;
+ __state_ &= ~__n_readers_;
+ __state_ |= __num_readers;
+ return true;
+}
+
+template <class _Mutex>
+class shared_lock
+{
+public:
+ typedef _Mutex mutex_type;
+
+private:
+ mutex_type* __m_;
+ bool __owns_;
+
+public:
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock() noexcept
+ : __m_(nullptr),
+ __owns_(false)
+ {}
+
+ _LIBCPP_INLINE_VISIBILITY
+ explicit shared_lock(mutex_type& __m)
+ : __m_(&__m),
+ __owns_(true)
+ {__m_->lock_shared();}
+
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock(mutex_type& __m, defer_lock_t) noexcept
+ : __m_(&__m),
+ __owns_(false)
+ {}
+
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock(mutex_type& __m, try_to_lock_t)
+ : __m_(&__m),
+ __owns_(__m.try_lock_shared())
+ {}
+
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock(mutex_type& __m, adopt_lock_t)
+ : __m_(&__m),
+ __owns_(true)
+ {}
+
+ template <class _Clock, class _Duration>
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock(mutex_type& __m,
+ const chrono::time_point<_Clock, _Duration>& __abs_time)
+ : __m_(&__m),
+ __owns_(__m.try_lock_shared_until(__abs_time))
+ {}
+
+ template <class _Rep, class _Period>
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock(mutex_type& __m,
+ const chrono::duration<_Rep, _Period>& __rel_time)
+ : __m_(&__m),
+ __owns_(__m.try_lock_shared_for(__rel_time))
+ {}
+
+ _LIBCPP_INLINE_VISIBILITY
+ ~shared_lock()
+ {
+ if (__owns_)
+ __m_->unlock_shared();
+ }
+
+ shared_lock(shared_lock const&) = delete;
+ shared_lock& operator=(shared_lock const&) = delete;
+
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock(shared_lock&& __u) noexcept
+ : __m_(__u.__m_),
+ __owns_(__u.__owns_)
+ {
+ __u.__m_ = nullptr;
+ __u.__owns_ = false;
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ shared_lock& operator=(shared_lock&& __u) noexcept
+ {
+ if (__owns_)
+ __m_->unlock_shared();
+ __m_ = nullptr;
+ __owns_ = false;
+ __m_ = __u.__m_;
+ __owns_ = __u.__owns_;
+ __u.__m_ = nullptr;
+ __u.__owns_ = false;
+ return *this;
+ }
+
+ void lock();
+ bool try_lock();
+ template <class Rep, class Period>
+ bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
+ template <class Clock, class Duration>
+ bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
+ void unlock();
+
+ // Setters
+ _LIBCPP_INLINE_VISIBILITY
+ void swap(shared_lock& __u) noexcept
+ {
+ _VSTD::swap(__m_, __u.__m_);
+ _VSTD::swap(__owns_, __u.__owns_);
+ }
+
+ _LIBCPP_INLINE_VISIBILITY
+ mutex_type* release() noexcept
+ {
+ mutex_type* __m = __m_;
+ __m_ = nullptr;
+ __owns_ = false;
+ return __m;
+ }
+
+ // Getters
+ _LIBCPP_INLINE_VISIBILITY
+ bool owns_lock() const noexcept {return __owns_;}
+
+ _LIBCPP_INLINE_VISIBILITY
+ explicit operator bool () const noexcept {return __owns_;}
+
+ _LIBCPP_INLINE_VISIBILITY
+ mutex_type* mutex() const noexcept {return __m_;}
+};
+
+template <class _Mutex>
+void
+shared_lock<_Mutex>::lock()
+{
+ if (__m_ == nullptr)
+ __throw_system_error(EPERM, "shared_lock::lock: references null mutex");
+ if (__owns_)
+ __throw_system_error(EDEADLK, "shared_lock::lock: already locked");
+ __m_->lock_shared();
+ __owns_ = true;
+}
+
+template <class _Mutex>
+bool
+shared_lock<_Mutex>::try_lock()
+{
+ if (__m_ == nullptr)
+ __throw_system_error(EPERM, "shared_lock::try_lock: references null mutex");
+ if (__owns_)
+ __throw_system_error(EDEADLK, "shared_lock::try_lock: already locked");
+ __owns_ = __m_->try_lock_shared();
+ return __owns_;
+}
+
+template <class _Mutex>
+template <class _Rep, class _Period>
+bool
+shared_lock<_Mutex>::try_lock_for(const chrono::duration<_Rep, _Period>& __d)
+{
+ if (__m_ == nullptr)
+ __throw_system_error(EPERM, "shared_lock::try_lock_for: references null mutex");
+ if (__owns_)
+ __throw_system_error(EDEADLK, "shared_lock::try_lock_for: already locked");
+ __owns_ = __m_->try_lock_shared_for(__d);
+ return __owns_;
+}
+
+template <class _Mutex>
+template <class _Clock, class _Duration>
+bool
+shared_lock<_Mutex>::try_lock_until(const chrono::time_point<_Clock, _Duration>& __t)
+{
+ if (__m_ == nullptr)
+ __throw_system_error(EPERM, "shared_lock::try_lock_until: references null mutex");
+ if (__owns_)
+ __throw_system_error(EDEADLK, "shared_lock::try_lock_until: already locked");
+ __owns_ = __m_->try_lock_shared_until(__t);
+ return __owns_;
+}
+
+template <class _Mutex>
+void
+shared_lock<_Mutex>::unlock()
+{
+ if (!__owns_)
+ __throw_system_error(EPERM, "shared_lock::unlock: not locked");
+ __m_->unlock_shared();
+ __owns_ = false;
+}
+
+template <class _Mutex>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+swap(shared_lock<_Mutex>& __x, shared_lock<_Mutex>& __y) noexcept
+ {__x.swap(__y);}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER > 11
+
+#endif // _LIBCPP_SHARED_MUTEX