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

1 files changed, 419 insertions, 0 deletions

diff --git a/include/shared_mutex b/include/shared_mutex
new file mode 100644
index 000000000..5b1f53aaf
--- /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