library/cpp/messagebus/latch.h


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#pragma once 
 
#include <util/system/condvar.h>
#include <util/system/mutex.h> 
 
class TLatch { 
private: 
    // 0 for unlocked, 1 for locked 
    TAtomic Locked; 
    TMutex Mutex; 
    TCondVar CondVar; 

public: 
    TLatch()
        : Locked(0)
    {
    }
 
    void Wait() { 
        // optimistic path 
        if (AtomicGet(Locked) == 0) { 
            return; 
        } 
 
        TGuard<TMutex> guard(Mutex); 
        while (AtomicGet(Locked) == 1) {
            CondVar.WaitI(Mutex); 
        } 
    } 
 
    bool TryWait() { 
        return AtomicGet(Locked) == 0; 
    } 
 
    void Unlock() { 
        // optimistic path 
        if (AtomicGet(Locked) == 0) { 
            return; 
        } 
 
        TGuard<TMutex> guard(Mutex); 
        AtomicSet(Locked, 0);
        CondVar.BroadCast(); 
    } 
 
    void Lock() { 
        AtomicSet(Locked, 1); 
    } 
 
    bool IsLocked() { 
        return AtomicGet(Locked); 
    } 
};