MacSemaphore.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 <dispatch/dispatch.h>
 
class FMacSemaphore
{
public:
    UE_NONCOPYABLE(FMacSemaphore);
 
    FMacSemaphore(int32 InitialCount, int32 /*MaxCount*/)
        : Semaphore(dispatch_semaphore_create(InitialCount))
    {
        checkfSlow(InitialCount >= 0, TEXT("Semaphore's initial count must be non negative value: %d"), InitialCount);
    }
    
    virtual ~FMacSemaphore()
    {
        dispatch_release(Semaphore);
    }
 
    void Acquire()
    {
        intptr_t Res = dispatch_semaphore_wait(Semaphore, DISPATCH_TIME_FOREVER);
        checkfSlow(Res == 0, TEXT("Acquiring semaphore failed"));
    }
 
    bool TryAcquire(FTimespan Timeout = FTimespan::Zero())
    {
        dispatch_time_t TS = dispatch_time(DISPATCH_TIME_NOW, (int64)Timeout.GetTotalMicroseconds() * 1000);
        intptr_t Res = dispatch_semaphore_wait(Semaphore, TS);
        return Res == 0;
    }
 
    void Release(int32 Count = 1)
    {
        checkfSlow(Count > 0, TEXT("Releasing semaphore with Count = %d, that should be greater than 0"), Count);
        for (int i = 0; i != Count; ++i)
        {
            dispatch_semaphore_signal(Semaphore);
        }
    }
 
private:
    dispatch_semaphore_t Semaphore;
};
 
typedef FMacSemaphore FSemaphore;