// ©2013-2016 Cameron Desrochers.
// Distributed under the simplified BSD license (see the license file that
// should have come with this header).
// Uses Jeff Preshing's semaphore implementation (under the terms of its
// separate zlib license, embedded below).

#pragma once

// Provides portable (VC++2010+, Intel ICC 13, GCC 4.7+, and anything C++11 compliant) implementation
// of low-level memory barriers, plus a few semi-portable utility macros (for inlining and alignment).
// Also has a basic atomic type (limited to hardware-supported atomics with no memory ordering guarantees).
// Uses the AE_* prefix for macros (historical reasons), and the "moodycamel" namespace for symbols.

#include <cerrno>
#include <cassert>
#include <type_traits>
#include <cerrno>
#include <cstdint>
#include <ctime>

// Platform detection
#if defined(__INTEL_COMPILER)
#define AE_ICC
#elif defined(_MSC_VER)
#define AE_VCPP
#elif defined(__GNUC__)
#define AE_GCC
#endif

#if defined(_M_IA64) || defined(__ia64__)
#define AE_ARCH_IA64
#elif defined(_WIN64) || defined(__amd64__) || defined(_M_X64) || defined(__x86_64__)
#define AE_ARCH_X64
#elif defined(_M_IX86) || defined(__i386__)
#define AE_ARCH_X86
#elif defined(_M_PPC) || defined(__powerpc__)
#define AE_ARCH_PPC
#else
#define AE_ARCH_UNKNOWN
#endif

// AE_UNUSED
#define AE_UNUSED(x) ((void) x)

// AE_NO_TSAN/AE_TSAN_ANNOTATE_*
#if defined(__has_feature)
#if __has_feature(thread_sanitizer)
#if __cplusplus >= 201703L // inline variables require C++17
namespace moodycamel
{
inline int ae_tsan_global;
}
#define AE_TSAN_ANNOTATE_RELEASE() AnnotateHappensBefore (__FILE__, __LINE__, (void*) (&::moodycamel::ae_tsan_global))
#define AE_TSAN_ANNOTATE_ACQUIRE() AnnotateHappensAfter (__FILE__, __LINE__, (void*) (&::moodycamel::ae_tsan_global))
extern "C" void AnnotateHappensBefore (const char*, int, void*);
extern "C" void AnnotateHappensAfter (const char*, int, void*);
#else // when we can't work with tsan, attempt to disable its warnings
#define AE_NO_TSAN __attribute__ ((no_sanitize ("thread")))
#endif
#endif
#endif
#ifndef AE_NO_TSAN
#define AE_NO_TSAN
#endif
#ifndef AE_TSAN_ANNOTATE_RELEASE
#define AE_TSAN_ANNOTATE_RELEASE()
#define AE_TSAN_ANNOTATE_ACQUIRE()
#endif

// AE_FORCEINLINE
#if defined(AE_VCPP) || defined(AE_ICC)
#define AE_FORCEINLINE __forceinline
#elif defined(AE_GCC)
//#define AE_FORCEINLINE __attribute__((always_inline))
#define AE_FORCEINLINE inline
#else
#define AE_FORCEINLINE inline
#endif

// AE_ALIGN
#if defined(AE_VCPP) || defined(AE_ICC)
#define AE_ALIGN(x) __declspec(align (x))
#elif defined(AE_GCC)
#define AE_ALIGN(x) __attribute__ ((aligned (x)))
#else
// Assume GCC compliant syntax...
#define AE_ALIGN(x) __attribute__ ((aligned (x)))
#endif

// Portable atomic fences implemented below:

namespace moodycamel
{
enum memory_order
{
    memory_order_relaxed,
    memory_order_acquire,
    memory_order_release,
    memory_order_acq_rel,
    memory_order_seq_cst,

    // memory_order_sync: Forces a full sync:
    // #LoadLoad, #LoadStore, #StoreStore, and most significantly, #StoreLoad
    memory_order_sync = memory_order_seq_cst
};

} // end namespace moodycamel

#if (defined(AE_VCPP) && (_MSC_VER < 1700 || defined(__cplusplus_cli))) || (defined(AE_ICC) && __INTEL_COMPILER < 1600)
// VS2010 and ICC13 don't support std::atomic_*_fence, implement our own fences

#include <intrin.h>

#if defined(AE_ARCH_X64) || defined(AE_ARCH_X86)
#define AeFullSync _mm_mfence
#define AeLiteSync _mm_mfence
#elif defined(AE_ARCH_IA64)
#define AeFullSync __mf
#define AeLiteSync __mf
#elif defined(AE_ARCH_PPC)
#include <ppcintrinsics.h>
#define AeFullSync __sync
#define AeLiteSync __lwsync
#endif

#ifdef AE_VCPP
#pragma warning(push)
#pragma warning(disable : 4365) // Disable erroneous 'conversion from long to unsigned int, signed/unsigned mismatch' error when using `assert`
#ifdef __cplusplus_cli
#pragma managed(push, off)
#endif
#endif

namespace moodycamel
{
AE_FORCEINLINE void compiler_fence (memory_order order) AE_NO_TSAN
{
    switch (order)
    {
        case memory_order_relaxed:
            break;
        case memory_order_acquire:
            _ReadBarrier();
            break;
        case memory_order_release:
            _WriteBarrier();
            break;
        case memory_order_acq_rel:
            _ReadWriteBarrier();
            break;
        case memory_order_seq_cst:
            _ReadWriteBarrier();
            break;
        default:
            assert (false);
    }
}

// x86/x64 have a strong memory model -- all loads and stores have
// acquire and release semantics automatically (so only need compiler
// barriers for those).
#if defined(AE_ARCH_X86) || defined(AE_ARCH_X64)
AE_FORCEINLINE void fence (memory_order order) AE_NO_TSAN
{
    switch (order)
    {
        case memory_order_relaxed:
            break;
        case memory_order_acquire:
            _ReadBarrier();
            break;
        case memory_order_release:
            _WriteBarrier();
            break;
        case memory_order_acq_rel:
            _ReadWriteBarrier();
            break;
        case memory_order_seq_cst:
            _ReadWriteBarrier();
            AeFullSync();
            _ReadWriteBarrier();
            break;
        default:
            assert (false);
    }
}
#else
AE_FORCEINLINE void fence (memory_order order) AE_NO_TSAN
{
    // Non-specialized arch, use heavier memory barriers everywhere just in case :-(
    switch (order)
    {
        case memory_order_relaxed:
            break;
        case memory_order_acquire:
            _ReadBarrier();
            AeLiteSync();
            _ReadBarrier();
            break;
        case memory_order_release:
            _WriteBarrier();
            AeLiteSync();
            _WriteBarrier();
            break;
        case memory_order_acq_rel:
            _ReadWriteBarrier();
            AeLiteSync();
            _ReadWriteBarrier();
            break;
        case memory_order_seq_cst:
            _ReadWriteBarrier();
            AeFullSync();
            _ReadWriteBarrier();
            break;
        default:
            assert (false);
    }
}
#endif
} // end namespace moodycamel
#else
// Use standard library of atomics
#include <atomic>

namespace moodycamel
{
AE_FORCEINLINE void compiler_fence (memory_order order) AE_NO_TSAN
{
    switch (order)
    {
        case memory_order_relaxed:
            break;
        case memory_order_acquire:
            std::atomic_signal_fence (std::memory_order_acquire);
            break;
        case memory_order_release:
            std::atomic_signal_fence (std::memory_order_release);
            break;
        case memory_order_acq_rel:
            std::atomic_signal_fence (std::memory_order_acq_rel);
            break;
        case memory_order_seq_cst:
            std::atomic_signal_fence (std::memory_order_seq_cst);
            break;
        default:
            assert (false);
    }
}

AE_FORCEINLINE void fence (memory_order order) AE_NO_TSAN
{
    switch (order)
    {
        case memory_order_relaxed:
            break;
        case memory_order_acquire:
            AE_TSAN_ANNOTATE_ACQUIRE();
            std::atomic_thread_fence (std::memory_order_acquire);
            break;
        case memory_order_release:
            AE_TSAN_ANNOTATE_RELEASE();
            std::atomic_thread_fence (std::memory_order_release);
            break;
        case memory_order_acq_rel:
            AE_TSAN_ANNOTATE_ACQUIRE();
            AE_TSAN_ANNOTATE_RELEASE();
            std::atomic_thread_fence (std::memory_order_acq_rel);
            break;
        case memory_order_seq_cst:
            AE_TSAN_ANNOTATE_ACQUIRE();
            AE_TSAN_ANNOTATE_RELEASE();
            std::atomic_thread_fence (std::memory_order_seq_cst);
            break;
        default:
            assert (false);
    }
}

} // end namespace moodycamel

#endif

#if ! defined(AE_VCPP) || (_MSC_VER >= 1700 && ! defined(__cplusplus_cli))
#define AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
#endif

#ifdef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
#include <atomic>
#endif
#include <utility>

// WARNING: *NOT* A REPLACEMENT FOR std::atomic. READ CAREFULLY:
// Provides basic support for atomic variables -- no memory ordering guarantees are provided.
// The guarantee of atomicity is only made for types that already have atomic load and store guarantees
// at the hardware level -- on most platforms this generally means aligned pointers and integers (only).
namespace moodycamel
{
template <typename T>
class weak_atomic
{
public:
    AE_NO_TSAN weak_atomic() : value() {}
#ifdef AE_VCPP
#pragma warning(push)
#pragma warning(disable : 4100) // Get rid of (erroneous) 'unreferenced formal parameter' warning
#endif
    template <typename U>
    AE_NO_TSAN weak_atomic (U&& x) : value (std::forward<U> (x))
    {
    }
#ifdef __cplusplus_cli
    // Work around bug with universal reference/nullptr combination that only appears when /clr is on
    AE_NO_TSAN weak_atomic (nullptr_t) : value (nullptr) {}
#endif
    AE_NO_TSAN weak_atomic (weak_atomic const& other) : value (other.load())
    {
    }
    AE_NO_TSAN weak_atomic (weak_atomic&& other) : value (std::move (other.load())) {}
#ifdef AE_VCPP
#pragma warning(pop)
#endif

    AE_FORCEINLINE operator T() const AE_NO_TSAN
    {
        return load();
    }

#ifndef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
    template <typename U>
    AE_FORCEINLINE weak_atomic const& operator= (U&& x) AE_NO_TSAN
    {
        value = std::forward<U> (x);
        return *this;
    }
    AE_FORCEINLINE weak_atomic const& operator= (weak_atomic const& other) AE_NO_TSAN
    {
        value = other.value;
        return *this;
    }

    AE_FORCEINLINE T load() const AE_NO_TSAN { return value; }

    AE_FORCEINLINE T fetch_add_acquire (T increment) AE_NO_TSAN
    {
#if defined(AE_ARCH_X64) || defined(AE_ARCH_X86)
        if (sizeof (T) == 4)
            return _InterlockedExchangeAdd ((long volatile*) &value, (long) increment);
#if defined(_M_AMD64)
        else if (sizeof (T) == 8)
            return _InterlockedExchangeAdd64 ((long long volatile*) &value, (long long) increment);
#endif
#else
#error Unsupported platform
#endif
        assert (false && "T must be either a 32 or 64 bit type");
        return value;
    }

    AE_FORCEINLINE T fetch_add_release (T increment) AE_NO_TSAN
    {
#if defined(AE_ARCH_X64) || defined(AE_ARCH_X86)
        if (sizeof (T) == 4)
            return _InterlockedExchangeAdd ((long volatile*) &value, (long) increment);
#if defined(_M_AMD64)
        else if (sizeof (T) == 8)
            return _InterlockedExchangeAdd64 ((long long volatile*) &value, (long long) increment);
#endif
#else
#error Unsupported platform
#endif
        assert (false && "T must be either a 32 or 64 bit type");
        return value;
    }
#else
    template <typename U>
    AE_FORCEINLINE weak_atomic const& operator= (U&& x) AE_NO_TSAN
    {
        value.store (std::forward<U> (x), std::memory_order_relaxed);
        return *this;
    }

    AE_FORCEINLINE weak_atomic const& operator= (weak_atomic const& other) AE_NO_TSAN
    {
        value.store (other.value.load (std::memory_order_relaxed), std::memory_order_relaxed);
        return *this;
    }

    AE_FORCEINLINE T load() const AE_NO_TSAN { return value.load (std::memory_order_relaxed); }

    AE_FORCEINLINE T fetch_add_acquire (T increment) AE_NO_TSAN
    {
        return value.fetch_add (increment, std::memory_order_acquire);
    }

    AE_FORCEINLINE T fetch_add_release (T increment) AE_NO_TSAN
    {
        return value.fetch_add (increment, std::memory_order_release);
    }
#endif

private:
#ifndef AE_USE_STD_ATOMIC_FOR_WEAK_ATOMIC
    // No std::atomic support, but still need to circumvent compiler optimizations.
    // `volatile` will make memory access slow, but is guaranteed to be reliable.
    volatile T value;
#else
    std::atomic<T> value;
#endif
};

} // end namespace moodycamel

// Portable single-producer, single-consumer semaphore below:

#if defined(_WIN32)
// Avoid including windows.h in a header; we only need a handful of
// items, so we'll redeclare them here (this is relatively safe since
// the API generally has to remain stable between Windows versions).
// I know this is an ugly hack but it still beats polluting the global
// namespace with thousands of generic names or adding a .cpp for nothing.
extern "C"
{
    struct _SECURITY_ATTRIBUTES;
    __declspec(dllimport) void* __stdcall CreateSemaphoreW (_SECURITY_ATTRIBUTES* lpSemaphoreAttributes, long lInitialCount, long lMaximumCount, const wchar_t* lpName);
    __declspec(dllimport) int __stdcall CloseHandle (void* hObject);
    __declspec(dllimport) unsigned long __stdcall WaitForSingleObject (void* hHandle, unsigned long dwMilliseconds);
    __declspec(dllimport) int __stdcall ReleaseSemaphore (void* hSemaphore, long lReleaseCount, long* lpPreviousCount);
}
#elif defined(__MACH__)
#include <mach/mach.h>
#elif defined(__unix__)
#include <semaphore.h>
#elif defined(FREERTOS)
#include <FreeRTOS.h>
#include <semphr.h>
#include <task.h>
#endif

namespace moodycamel
{
// Code in the spsc_sema namespace below is an adaptation of Jeff Preshing's
// portable + lightweight semaphore implementations, originally from
// https://github.com/preshing/cpp11-on-multicore/blob/master/common/sema.h
// LICENSE:
// Copyright (c) 2015 Jeff Preshing
//
// This software is provided 'as-is', without any express or implied
// warranty. In no event will the authors be held liable for any damages
// arising from the use of this software.
//
// Permission is granted to anyone to use this software for any purpose,
// including commercial applications, and to alter it and redistribute it
// freely, subject to the following restrictions:
//
// 1. The origin of this software must not be misrepresented; you must not
//    claim that you wrote the original software. If you use this software
//    in a product, an acknowledgement in the product documentation would be
//    appreciated but is not required.
// 2. Altered source versions must be plainly marked as such, and must not be
//    misrepresented as being the original software.
// 3. This notice may not be removed or altered from any source distribution.
namespace spsc_sema
{
#if defined(_WIN32)
    class Semaphore
    {
    private:
        void* m_hSema;

        Semaphore (const Semaphore& other);
        Semaphore& operator= (const Semaphore& other);

    public:
        AE_NO_TSAN Semaphore (int initialCount = 0) : m_hSema()
        {
            assert (initialCount >= 0);
            const long maxLong = 0x7fffffff;
            m_hSema = CreateSemaphoreW (nullptr, initialCount, maxLong, nullptr);
            assert (m_hSema);
        }

        AE_NO_TSAN ~Semaphore()
        {
            CloseHandle (m_hSema);
        }

        bool wait() AE_NO_TSAN
        {
            const unsigned long infinite = 0xffffffff;
            return WaitForSingleObject (m_hSema, infinite) == 0;
        }

        bool try_wait() AE_NO_TSAN
        {
            return WaitForSingleObject (m_hSema, 0) == 0;
        }

        bool timed_wait (std::uint64_t usecs) AE_NO_TSAN
        {
            return WaitForSingleObject (m_hSema, (unsigned long) (usecs / 1000)) == 0;
        }

        void signal (int count = 1) AE_NO_TSAN
        {
            while (! ReleaseSemaphore (m_hSema, count, nullptr))
                ;
        }
    };
#elif defined(__MACH__)
    //---------------------------------------------------------
    // Semaphore (Apple iOS and OSX)
    // Can't use POSIX semaphores due to http://lists.apple.com/archives/darwin-kernel/2009/Apr/msg00010.html
    //---------------------------------------------------------
    class Semaphore
    {
    private:
        semaphore_t m_sema;

        Semaphore (const Semaphore& other);
        Semaphore& operator= (const Semaphore& other);

    public:
        AE_NO_TSAN Semaphore (int initialCount = 0) : m_sema()
        {
            assert (initialCount >= 0);
            kern_return_t rc = semaphore_create (mach_task_self(), &m_sema, SYNC_POLICY_FIFO, initialCount);
            assert (rc == KERN_SUCCESS);
            AE_UNUSED (rc);
        }

        AE_NO_TSAN ~Semaphore()
        {
            semaphore_destroy (mach_task_self(), m_sema);
        }

        bool wait() AE_NO_TSAN
        {
            return semaphore_wait (m_sema) == KERN_SUCCESS;
        }

        bool try_wait() AE_NO_TSAN
        {
            return timed_wait (0);
        }

        bool timed_wait (std::uint64_t timeout_usecs) AE_NO_TSAN
        {
            mach_timespec_t ts;
            ts.tv_sec = static_cast<unsigned int> (timeout_usecs / 1000000);
            ts.tv_nsec = static_cast<int> ((timeout_usecs % 1000000) * 1000);

            // added in OSX 10.10: https://developer.apple.com/library/prerelease/mac/documentation/General/Reference/APIDiffsMacOSX10_10SeedDiff/modules/Darwin.html
            kern_return_t rc = semaphore_timedwait (m_sema, ts);
            return rc == KERN_SUCCESS;
        }

        void signal() AE_NO_TSAN
        {
            while (semaphore_signal (m_sema) != KERN_SUCCESS)
                ;
        }

        void signal (int count) AE_NO_TSAN
        {
            while (count-- > 0)
            {
                while (semaphore_signal (m_sema) != KERN_SUCCESS)
                    ;
            }
        }
    };
#elif defined(__unix__)
    //---------------------------------------------------------
    // Semaphore (POSIX, Linux)
    //---------------------------------------------------------
    class Semaphore
    {
    private:
        sem_t m_sema;

        Semaphore (const Semaphore& other);
        Semaphore& operator= (const Semaphore& other);

    public:
        AE_NO_TSAN Semaphore (int initialCount = 0) : m_sema()
        {
            assert (initialCount >= 0);
            int rc = sem_init (&m_sema, 0, static_cast<unsigned int> (initialCount));
            assert (rc == 0);
            AE_UNUSED (rc);
        }

        AE_NO_TSAN ~Semaphore()
        {
            sem_destroy (&m_sema);
        }

        bool wait() AE_NO_TSAN
        {
            // http://stackoverflow.com/questions/2013181/gdb-causes-sem-wait-to-fail-with-eintr-error
            int rc;
            do
            {
                rc = sem_wait (&m_sema);
            } while (rc == -1 && errno == EINTR);
            return rc == 0;
        }

        bool try_wait() AE_NO_TSAN
        {
            int rc;
            do
            {
                rc = sem_trywait (&m_sema);
            } while (rc == -1 && errno == EINTR);
            return rc == 0;
        }

        bool timed_wait (std::uint64_t usecs) AE_NO_TSAN
        {
            struct timespec ts;
            const int usecs_in_1_sec = 1000000;
            const int nsecs_in_1_sec = 1000000000;
            clock_gettime (CLOCK_REALTIME, &ts);
            ts.tv_sec += static_cast<time_t> (usecs / usecs_in_1_sec);
            ts.tv_nsec += static_cast<long> (usecs % usecs_in_1_sec) * 1000;
            // sem_timedwait bombs if you have more than 1e9 in tv_nsec
            // so we have to clean things up before passing it in
            if (ts.tv_nsec >= nsecs_in_1_sec)
            {
                ts.tv_nsec -= nsecs_in_1_sec;
                ++ts.tv_sec;
            }

            int rc;
            do
            {
                rc = sem_timedwait (&m_sema, &ts);
            } while (rc == -1 && errno == EINTR);
            return rc == 0;
        }

        void signal() AE_NO_TSAN
        {
            while (sem_post (&m_sema) == -1)
                ;
        }

        void signal (int count) AE_NO_TSAN
        {
            while (count-- > 0)
            {
                while (sem_post (&m_sema) == -1)
                    ;
            }
        }
    };
#elif defined(FREERTOS)
    //---------------------------------------------------------
    // Semaphore (FreeRTOS)
    //---------------------------------------------------------
    class Semaphore
    {
    private:
        SemaphoreHandle_t m_sema;

        Semaphore (const Semaphore& other);
        Semaphore& operator= (const Semaphore& other);

    public:
        AE_NO_TSAN Semaphore (int initialCount = 0) : m_sema()
        {
            assert (initialCount >= 0);
            m_sema = xSemaphoreCreateCounting (static_cast<UBaseType_t> (~0ull), static_cast<UBaseType_t> (initialCount));
            assert (m_sema);
        }

        AE_NO_TSAN ~Semaphore()
        {
            vSemaphoreDelete (m_sema);
        }

        bool wait() AE_NO_TSAN
        {
            return xSemaphoreTake (m_sema, portMAX_DELAY) == pdTRUE;
        }

        bool try_wait() AE_NO_TSAN
        {
            // Note: In an ISR context, if this causes a task to unblock,
            // the caller won't know about it
            if (xPortIsInsideInterrupt())
                return xSemaphoreTakeFromISR (m_sema, NULL) == pdTRUE;
            return xSemaphoreTake (m_sema, 0) == pdTRUE;
        }

        bool timed_wait (std::uint64_t usecs) AE_NO_TSAN
        {
            std::uint64_t msecs = usecs / 1000;
            TickType_t ticks = static_cast<TickType_t> (msecs / portTICK_PERIOD_MS);
            if (ticks == 0)
                return try_wait();
            return xSemaphoreTake (m_sema, ticks) == pdTRUE;
        }

        void signal() AE_NO_TSAN
        {
            // Note: In an ISR context, if this causes a task to unblock,
            // the caller won't know about it
            BaseType_t rc;
            if (xPortIsInsideInterrupt())
                rc = xSemaphoreGiveFromISR (m_sema, NULL);
            else
                rc = xSemaphoreGive (m_sema);
            assert (rc == pdTRUE);
            AE_UNUSED (rc);
        }

        void signal (int count) AE_NO_TSAN
        {
            while (count-- > 0)
                signal();
        }
    };
#else
#error Unsupported platform! (No semaphore wrapper available)
#endif

    //---------------------------------------------------------
    // LightweightSemaphore
    //---------------------------------------------------------
    class LightweightSemaphore
    {
    public:
        typedef std::make_signed<std::size_t>::type ssize_t;

    private:
        weak_atomic<ssize_t> m_count;
        Semaphore m_sema;

        bool waitWithPartialSpinning (std::int64_t timeout_usecs = -1) AE_NO_TSAN
        {
            ssize_t oldCount;
            // Is there a better way to set the initial spin count?
            // If we lower it to 1000, testBenaphore becomes 15x slower on my Core i7-5930K Windows PC,
            // as threads start hitting the kernel semaphore.
            int spin = 1024;
            while (--spin >= 0)
            {
                if (m_count.load() > 0)
                {
                    m_count.fetch_add_acquire (-1);
                    return true;
                }
                compiler_fence (memory_order_acquire); // Prevent the compiler from collapsing the loop.
            }
            oldCount = m_count.fetch_add_acquire (-1);
            if (oldCount > 0)
                return true;
            if (timeout_usecs < 0)
            {
                if (m_sema.wait())
                    return true;
            }
            if (timeout_usecs > 0 && m_sema.timed_wait (static_cast<uint64_t> (timeout_usecs)))
                return true;
            // At this point, we've timed out waiting for the semaphore, but the
            // count is still decremented indicating we may still be waiting on
            // it. So we have to re-adjust the count, but only if the semaphore
            // wasn't signaled enough times for us too since then. If it was, we
            // need to release the semaphore too.
            while (true)
            {
                oldCount = m_count.fetch_add_release (1);
                if (oldCount < 0)
                    return false; // successfully restored things to the way they were
                // Oh, the producer thread just signaled the semaphore after all. Try again:
                oldCount = m_count.fetch_add_acquire (-1);
                if (oldCount > 0 && m_sema.try_wait())
                    return true;
            }
        }

    public:
        AE_NO_TSAN LightweightSemaphore (ssize_t initialCount = 0) : m_count (initialCount), m_sema()
        {
            assert (initialCount >= 0);
        }

        bool tryWait() AE_NO_TSAN
        {
            if (m_count.load() > 0)
            {
                m_count.fetch_add_acquire (-1);
                return true;
            }
            return false;
        }

        bool wait() AE_NO_TSAN
        {
            return tryWait() || waitWithPartialSpinning();
        }

        bool wait (std::int64_t timeout_usecs) AE_NO_TSAN
        {
            return tryWait() || waitWithPartialSpinning (timeout_usecs);
        }

        void signal (ssize_t count = 1) AE_NO_TSAN
        {
            assert (count >= 0);
            ssize_t oldCount = m_count.fetch_add_release (count);
            assert (oldCount >= -1);
            if (oldCount < 0)
            {
                m_sema.signal (1);
            }
        }

        std::size_t availableApprox() const AE_NO_TSAN
        {
            ssize_t count = m_count.load();
            return count > 0 ? static_cast<std::size_t> (count) : 0;
        }
    };
} // end namespace spsc_sema
} // end namespace moodycamel

#if defined(AE_VCPP) && (_MSC_VER < 1700 || defined(__cplusplus_cli))
#pragma warning(pop)
#ifdef __cplusplus_cli
#pragma managed(pop)
#endif
#endif
