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llvm-project/libcxx/include/shared_mutex

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// -*- 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
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