MultiUniqueLock.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Algo/Sort.h"
#include "Containers/Array.h"
 
namespace UE
{
 
// Like TUniqueLock, but acquires multiple locks and holds then until destruction. Acquires the locks in address
// order to prevent deadlocks if multiple threads are using TMultiUniqueLock for similar sets of locks.
template<typename TLockType>
class TMultiUniqueLock final
{
public:
    explicit TMultiUniqueLock(const TArray<TLockType*>& Locks)
        : Locks(Locks)
    {
        SortAndLock();
    }
 
    explicit TMultiUniqueLock(TArray<TLockType*>&& Locks)
        : Locks(MoveTemp(Locks))
    {
        SortAndLock();
    }
 
    TMultiUniqueLock& operator=(const TArray<TLockType*>&) = delete;
    TMultiUniqueLock& operator=(TArray<TLockType*>&&) = delete;
 
    ~TMultiUniqueLock()
    {
        for (TLockType* Lock : Locks)
        {
            Lock->Unlock();
        }
    }
 
private:
    void SortAndLock()
    {
        Algo::Sort(Locks);
        for (TLockType* Lock : Locks)
        {
            Lock->Lock();
        }
    }
 
    TArray<TLockType*> Locks;
};
 
}