mingw.condition_variable.h

/**
* @file condition_variable.h
* @brief std::condition_variable implementation for MinGW
*
* (c) 2013-2016 by Mega Limited, Auckland, New Zealand
* @author Alexander Vassilev
*
* @copyright Simplified (2-clause) BSD License.
* You should have received a copy of the license along with this
* program.
*
* This code 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.
* @note
* This file may become part of the mingw-w64 runtime package. If/when this happens,
* the appropriate license will be added, i.e. this code will become dual-licensed,
* and the current BSD 2-clause license will stay.
*/

#ifndef MINGW_CONDITIONAL_VARIABLE_H
#define MINGW_CONDITIONAL_VARIABLE_H

#if !defined(__cplusplus) || (__cplusplus < 201103L)
#error A C++11 compiler is required!
#endif
//  Use the standard classes for std::, if available.
#include <condition_variable>

#include <cassert>
#include <chrono>
#include <system_error>

#include <sdkddkver.h>  //  Detect Windows version.
#if (WINVER < _WIN32_WINNT_VISTA)
#include <atomic>
#endif
#if (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR))
#pragma message "The Windows API that MinGW-w32 provides is not fully compatible\
 with Microsoft's API. We'll try to work around this, but we can make no\
 guarantees. This problem does not exist in MinGW-w64."
#include <windows.h>    //  No further granularity can be expected.
#else
#if (WINVER < _WIN32_WINNT_VISTA)
#include <windef.h>
#include <winbase.h>  //  For CreateSemaphore
#include <handleapi.h>
#endif
#include <synchapi.h>
#endif

#include "mingw.mutex.h"
#include "mingw.shared_mutex.h"

#if !defined(_WIN32_WINNT) || (_WIN32_WINNT < 0x0501)
#error To use the MinGW-std-threads library, you will need to define the macro _WIN32_WINNT to be 0x0501 (Windows XP) or higher.
#endif

namespace mingw_stdthread
{
#if defined(__MINGW32__ ) && !defined(_GLIBCXX_HAS_GTHREADS) && !defined(__clang__)
enum class cv_status { no_timeout, timeout };
#else
using std::cv_status;
#endif
namespace xp
{
//    Include the XP-compatible condition_variable classes only if actually
//  compiling for XP. The XP-compatible classes are slower than the newer
//  versions, and depend on features not compatible with Windows Phone 8.
#if (WINVER < _WIN32_WINNT_VISTA)
class condition_variable_any
{
    recursive_mutex mMutex {};
    std::atomic<int> mNumWaiters {0};
    HANDLE mSemaphore;
    HANDLE mWakeEvent {};
public:
    using native_handle_type = HANDLE;
    native_handle_type native_handle()
    {
        return mSemaphore;
    }
    condition_variable_any(const condition_variable_any&) = delete;
    condition_variable_any& operator=(const condition_variable_any&) = delete;
    condition_variable_any()
        :   mSemaphore(CreateSemaphoreA(NULL, 0, 0xFFFF, NULL))
    {
        if (mSemaphore == NULL)
            __builtin_trap();
        mWakeEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
        if (mWakeEvent == NULL)
        {
            CloseHandle(mSemaphore);
            __builtin_trap();
        }
    }
    ~condition_variable_any()
    {
        CloseHandle(mWakeEvent);
        CloseHandle(mSemaphore);
    }
private:
    template <class M>
    bool wait_impl(M& lock, DWORD timeout)
    {
        {
            lock_guard<recursive_mutex> guard(mMutex);
            mNumWaiters++;
        }
        lock.unlock();
        DWORD ret = WaitForSingleObject(mSemaphore, timeout);

        mNumWaiters--;
        SetEvent(mWakeEvent);
        lock.lock();
        if (ret == WAIT_OBJECT_0)
            return true;
        else if (ret == WAIT_TIMEOUT)
            return false;
//2 possible cases:
//1)The point in notify_all() where we determine the count to
//increment the semaphore with has not been reached yet:
//we just need to decrement mNumWaiters, but setting the event does not hurt
//
//2)Semaphore has just been released with mNumWaiters just before
//we decremented it. This means that the semaphore count
//after all waiters finish won't be 0 - because not all waiters
//woke up by acquiring the semaphore - we woke up by a timeout.
//The notify_all() must handle this gracefully
//
        else
        {
            using namespace std;
            __builtin_trap();
        }
    }
public:
    template <class M>
    void wait(M& lock)
    {
        wait_impl(lock, INFINITE);
    }
    template <class M, class Predicate>
    void wait(M& lock, Predicate pred)
    {
        while(!pred())
        {
            wait(lock);
        };
    }

    void notify_all() noexcept
    {
        lock_guard<recursive_mutex> lock(mMutex); //block any further wait requests until all current waiters are unblocked
        if (mNumWaiters.load() <= 0)
            return;

        ReleaseSemaphore(mSemaphore, mNumWaiters, NULL);
        while(mNumWaiters > 0)
        {
            auto ret = WaitForSingleObject(mWakeEvent, 1000);
            if (ret == WAIT_FAILED || ret == WAIT_ABANDONED)
                std::terminate();
        }
        assert(mNumWaiters == 0);
//in case some of the waiters timed out just after we released the
//semaphore by mNumWaiters, it won't be zero now, because not all waiters
//woke up by acquiring the semaphore. So we must zero the semaphore before
//we accept waiters for the next event
//See _wait_impl for details
        while(WaitForSingleObject(mSemaphore, 0) == WAIT_OBJECT_0);
    }
    void notify_one() noexcept
    {
        lock_guard<recursive_mutex> lock(mMutex);
        int targetWaiters = mNumWaiters.load() - 1;
        if (targetWaiters <= -1)
            return;
        ReleaseSemaphore(mSemaphore, 1, NULL);
        while(mNumWaiters > targetWaiters)
        {
            auto ret = WaitForSingleObject(mWakeEvent, 1000);
            if (ret == WAIT_FAILED || ret == WAIT_ABANDONED)
                std::terminate();
        }
        assert(mNumWaiters == targetWaiters);
    }
    template <class M, class Rep, class Period>
    cv_status wait_for(M& lock,
                       const std::chrono::duration<Rep, Period>& rel_time)
    {
        using namespace std::chrono;
        auto timeout = duration_cast<milliseconds>(rel_time).count();
        DWORD waittime = (timeout < INFINITE) ? ((timeout < 0) ? 0 : static_cast<DWORD>(timeout)) : (INFINITE - 1);
        bool ret = wait_impl(lock, waittime) || (timeout >= INFINITE);
        return ret?cv_status::no_timeout:cv_status::timeout;
    }

    template <class M, class Rep, class Period, class Predicate>
    bool wait_for(M& lock,
                  const std::chrono::duration<Rep, Period>& rel_time, Predicate pred)
    {
        return wait_until(lock, std::chrono::steady_clock::now()+rel_time, pred);
    }
    template <class M, class Clock, class Duration>
    cv_status wait_until (M& lock,
                          const std::chrono::time_point<Clock,Duration>& abs_time)
    {
        return wait_for(lock, abs_time - Clock::now());
    }
    template <class M, class Clock, class Duration, class Predicate>
    bool wait_until (M& lock,
                     const std::chrono::time_point<Clock, Duration>& abs_time,
                     Predicate pred)
    {
        while (!pred())
        {
            if (wait_until(lock, abs_time) == cv_status::timeout)
            {
                return pred();
            }
        }
        return true;
    }
};
class condition_variable: condition_variable_any
{
    using base = condition_variable_any;
public:
    using base::native_handle_type;
    using base::native_handle;
    using base::base;
    using base::notify_all;
    using base::notify_one;
    void wait(unique_lock<mutex> &lock)
    {
        base::wait(lock);
    }
    template <class Predicate>
    void wait(unique_lock<mutex>& lock, Predicate pred)
    {
        base::wait(lock, pred);
    }
    template <class Rep, class Period>
    cv_status wait_for(unique_lock<mutex>& lock, const std::chrono::duration<Rep, Period>& rel_time)
    {
        return base::wait_for(lock, rel_time);
    }
    template <class Rep, class Period, class Predicate>
    bool wait_for(unique_lock<mutex>& lock, const std::chrono::duration<Rep, Period>& rel_time, Predicate pred)
    {
        return base::wait_for(lock, rel_time, pred);
    }
    template <class Clock, class Duration>
    cv_status wait_until (unique_lock<mutex>& lock, const std::chrono::time_point<Clock,Duration>& abs_time)
    {
        return base::wait_until(lock, abs_time);
    }
    template <class Clock, class Duration, class Predicate>
    bool wait_until (unique_lock<mutex>& lock, const std::chrono::time_point<Clock, Duration>& abs_time, Predicate pred)
    {
        return base::wait_until(lock, abs_time, pred);
    }
};
#endif  //  Compiling for XP
} //  Namespace mingw_stdthread::xp

#if (WINVER >= _WIN32_WINNT_VISTA)
namespace vista
{
//  If compiling for Vista or higher, use the native condition variable.
class condition_variable
{
    static constexpr DWORD kInfinite = 0xffffffffl;
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
    CONDITION_VARIABLE cvariable_ = CONDITION_VARIABLE_INIT;
#pragma GCC diagnostic pop

    friend class condition_variable_any;

#if STDMUTEX_RECURSION_CHECKS
    template<typename MTX>
    inline static void before_wait (MTX * pmutex)
    {
        pmutex->mOwnerThread.checkSetOwnerBeforeUnlock();
    }
    template<typename MTX>
    inline static void after_wait (MTX * pmutex)
    {
        pmutex->mOwnerThread.setOwnerAfterLock(GetCurrentThreadId());
    }
#else
    inline static void before_wait (void *) { }
    inline static void after_wait (void *) { }
#endif

    bool wait_impl (unique_lock<xp::mutex> & lock, DWORD time)
    {
        using mutex_handle_type = typename xp::mutex::native_handle_type;
        static_assert(std::is_same<mutex_handle_type, PCRITICAL_SECTION>::value,
                      "Native Win32 condition variable requires std::mutex to \
use native Win32 critical section objects.");
        xp::mutex * pmutex = lock.release();
        before_wait(pmutex);
        BOOL success = SleepConditionVariableCS(&cvariable_,
                                                pmutex->native_handle(),
                                                time);
        after_wait(pmutex);
        lock = unique_lock<xp::mutex>(*pmutex, adopt_lock);
        return success;
    }

    bool wait_unique (windows7::mutex * pmutex, DWORD time)
    {
        before_wait(pmutex);
        BOOL success = SleepConditionVariableSRW( native_handle(),
                                                  pmutex->native_handle(),
                                                  time,
//    CONDITION_VARIABLE_LOCKMODE_SHARED has a value not specified by
//  Microsoft's Dev Center, but is known to be (convertible to) a ULONG. To
//  ensure that the value passed to this function is not equal to Microsoft's
//  constant, we can either use a static_assert, or simply generate an
//  appropriate value.
                                           !CONDITION_VARIABLE_LOCKMODE_SHARED);
        after_wait(pmutex);
        return success;
    }
    bool wait_impl (unique_lock<windows7::mutex> & lock, DWORD time)
    {
        windows7::mutex * pmutex = lock.release();
        bool success = wait_unique(pmutex, time);
        lock = unique_lock<windows7::mutex>(*pmutex, adopt_lock);
        return success;
    }
public:
    using native_handle_type = PCONDITION_VARIABLE;
    native_handle_type native_handle (void)
    {
        return &cvariable_;
    }

    condition_variable (void) = default;
    ~condition_variable (void) = default;

    condition_variable (const condition_variable &) = delete;
    condition_variable & operator= (const condition_variable &) = delete;

    void notify_one (void) noexcept
    {
        WakeConditionVariable(&cvariable_);
    }

    void notify_all (void) noexcept
    {
        WakeAllConditionVariable(&cvariable_);
    }

    void wait (unique_lock<mutex> & lock)
    {
        wait_impl(lock, kInfinite);
    }

    template<class Predicate>
    void wait (unique_lock<mutex> & lock, Predicate pred)
    {
        while (!pred())
            wait(lock);
    }

    template <class Rep, class Period>
    cv_status wait_for(unique_lock<mutex>& lock,
                       const std::chrono::duration<Rep, Period>& rel_time)
    {
        using namespace std::chrono;
        auto timeout = duration_cast<milliseconds>(rel_time).count();
        DWORD waittime = (timeout < kInfinite) ? ((timeout < 0) ? 0 : static_cast<DWORD>(timeout)) : (kInfinite - 1);
        bool result = wait_impl(lock, waittime) || (timeout >= kInfinite);
        return result ? cv_status::no_timeout : cv_status::timeout;
    }

    template <class Rep, class Period, class Predicate>
    bool wait_for(unique_lock<mutex>& lock,
                  const std::chrono::duration<Rep, Period>& rel_time,
                  Predicate pred)
    {
        return wait_until(lock,
                          std::chrono::steady_clock::now() + rel_time,
                          std::move(pred));
    }
    template <class Clock, class Duration>
    cv_status wait_until (unique_lock<mutex>& lock,
                          const std::chrono::time_point<Clock,Duration>& abs_time)
    {
        return wait_for(lock, abs_time - Clock::now());
    }
    template <class Clock, class Duration, class Predicate>
    bool wait_until  (unique_lock<mutex>& lock,
                      const std::chrono::time_point<Clock, Duration>& abs_time,
                      Predicate pred)
    {
        while (!pred())
        {
            if (wait_until(lock, abs_time) == cv_status::timeout)
            {
                return pred();
            }
        }
        return true;
    }
};

class condition_variable_any
{
    static constexpr DWORD kInfinite = 0xffffffffl;
    using native_shared_mutex = windows7::shared_mutex;

    condition_variable internal_cv_ {};
//    When available, the SRW-based mutexes should be faster than the
//  CriticalSection-based mutexes. Only try_lock will be unavailable in Vista,
//  and try_lock is not used by condition_variable_any.
    windows7::mutex internal_mutex_ {};

    template<class L>
    bool wait_impl (L & lock, DWORD time)
    {
        unique_lock<decltype(internal_mutex_)> internal_lock(internal_mutex_);
        lock.unlock();
        bool success = internal_cv_.wait_impl(internal_lock, time);
        lock.lock();
        return success;
    }
//    If the lock happens to be called on a native Windows mutex, skip any extra
//  contention.
    inline bool wait_impl (unique_lock<mutex> & lock, DWORD time)
    {
        return internal_cv_.wait_impl(lock, time);
    }
//    Some shared_mutex functionality is available even in Vista, but it's not
//  until Windows 7 that a full implementation is natively possible. The class
//  itself is defined, with missing features, at the Vista feature level.
    bool wait_impl (unique_lock<native_shared_mutex> & lock, DWORD time)
    {
        native_shared_mutex * pmutex = lock.release();
        bool success = internal_cv_.wait_unique(pmutex, time);
        lock = unique_lock<native_shared_mutex>(*pmutex, adopt_lock);
        return success;
    }
    bool wait_impl (shared_lock<native_shared_mutex> & lock, DWORD time)
    {
        native_shared_mutex * pmutex = lock.release();
        BOOL success = SleepConditionVariableSRW(native_handle(),
                       pmutex->native_handle(), time,
                       CONDITION_VARIABLE_LOCKMODE_SHARED);
        lock = shared_lock<native_shared_mutex>(*pmutex, adopt_lock);
        return success;
    }
public:
    using native_handle_type = typename condition_variable::native_handle_type;

    native_handle_type native_handle (void)
    {
        return internal_cv_.native_handle();
    }

    void notify_one (void) noexcept
    {
        internal_cv_.notify_one();
    }

    void notify_all (void) noexcept
    {
        internal_cv_.notify_all();
    }

    condition_variable_any (void) = default;
    ~condition_variable_any (void) = default;

    template<class L>
    void wait (L & lock)
    {
        wait_impl(lock, kInfinite);
    }

    template<class L, class Predicate>
    void wait (L & lock, Predicate pred)
    {
        while (!pred())
            wait(lock);
    }

    template <class L, class Rep, class Period>
    cv_status wait_for(L& lock, const std::chrono::duration<Rep,Period>& period)
    {
        using namespace std::chrono;
        auto timeout = duration_cast<milliseconds>(period).count();
        DWORD waittime = (timeout < kInfinite) ? ((timeout < 0) ? 0 : static_cast<DWORD>(timeout)) : (kInfinite - 1);
        bool result = wait_impl(lock, waittime) || (timeout >= kInfinite);
        return result ? cv_status::no_timeout : cv_status::timeout;
    }

    template <class L, class Rep, class Period, class Predicate>
    bool wait_for(L& lock, const std::chrono::duration<Rep, Period>& period,
                  Predicate pred)
    {
        return wait_until(lock, std::chrono::steady_clock::now() + period,
                          std::move(pred));
    }
    template <class L, class Clock, class Duration>
    cv_status wait_until (L& lock,
                          const std::chrono::time_point<Clock,Duration>& abs_time)
    {
        return wait_for(lock, abs_time - Clock::now());
    }
    template <class L, class Clock, class Duration, class Predicate>
    bool wait_until  (L& lock,
                      const std::chrono::time_point<Clock, Duration>& abs_time,
                      Predicate pred)
    {
        while (!pred())
        {
            if (wait_until(lock, abs_time) == cv_status::timeout)
            {
                return pred();
            }
        }
        return true;
    }
};
} //  Namespace vista
#endif
#if WINVER < 0x0600
using xp::condition_variable;
using xp::condition_variable_any;
#else
using vista::condition_variable;
using vista::condition_variable_any;
#endif
} //  Namespace mingw_stdthread

//  Push objects into std, but only if they are not already there.
namespace std
{
//    Because of quirks of the compiler, the common "using namespace std;"
//  directive would flatten the namespaces and introduce ambiguity where there
//  was none. Direct specification (std::), however, would be unaffected.
//    Take the safe option, and include only in the presence of MinGW's win32
//  implementation.
#if defined(__MINGW32__ ) && !defined(_GLIBCXX_HAS_GTHREADS) && !defined(__clang__)
using mingw_stdthread::cv_status;
using mingw_stdthread::condition_variable;
using mingw_stdthread::condition_variable_any;
#elif !defined(MINGW_STDTHREAD_REDUNDANCY_WARNING)  //  Skip repetition
#define MINGW_STDTHREAD_REDUNDANCY_WARNING
#pragma message "This version of MinGW seems to include a win32 port of\
 pthreads, and probably already has C++11 std threading classes implemented,\
 based on pthreads. These classes, found in namespace std, are not overridden\
 by the mingw-std-thread library. If you would still like to use this\
 implementation (as it is more lightweight), use the classes provided in\
 namespace mingw_stdthread."
#endif
}
#endif // MINGW_CONDITIONAL_VARIABLE_H