WindowsSemaphore.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreTypes.h"
#include "Misc/Timespan.h"
#include "Misc/AssertionMacros.h"
#include "Windows/AllowWindowsPlatformTypes.h"
 
class FWindowsSemaphore
{
public:
    UE_NONCOPYABLE(FWindowsSemaphore);
 
    FWindowsSemaphore(int32 InitialCount, int32 MaxCount)
        : Semaphore(CreateSemaphore(nullptr, InitialCount, MaxCount, nullptr))
    {
        checkfSlow(Semaphore, TEXT("CreateSemaphore failed: %u"), GetLastError());
    }
 
    ~FWindowsSemaphore()
    {
        CloseHandle(Semaphore);
    }
 
    void Acquire()
    {
        DWORD Res = WaitForSingleObject(Semaphore, INFINITE);
        checkfSlow(Res == WAIT_OBJECT_0, TEXT("Acquiring semaphore failed: %d (%u)"), Res, GetLastError());
    }
 
    bool TryAcquire(FTimespan Timeout = FTimespan::Zero())
    {
        DWORD Res = WaitForSingleObject(Semaphore, (DWORD)Timeout.GetTotalMilliseconds());
        checkfSlow(Res == WAIT_OBJECT_0 || Res == WAIT_TIMEOUT, TEXT("Acquiring semaphore failed: %d (%u)"), Res, GetLastError());
        return Res == WAIT_OBJECT_0;
    }
 
    void Release(int32 Count = 1)
    {
        checkfSlow(Count > 0, TEXT("Releasing semaphore with Count = %d, that should be greater than 0"), Count);
        bool bRes = ReleaseSemaphore(Semaphore, Count, nullptr);
        checkfSlow(bRes, TEXT("Releasing semaphore for %d failed: %u"), Count, GetLastError());
    }
 
private:
    HANDLE Semaphore;
};
 
using FSemaphore = FWindowsSemaphore;
 
#include "Windows/HideWindowsPlatformTypes.h"