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/*
* Copyright (C) 2007-2019 Xagasoft, All rights reserved.
*
* This file is part of the libbu++ library and is released under the
* terms of the license contained in the file LICENSE.
*/
#ifndef BU_COUNTER_EVENT_H
#define BU_COUNTER_EVENT_H
#include <pthread.h>
#include "bu/mutex.h"
#include "bu/condition.h"
namespace Bu
{
/**
* Represents a true/false state that controls thread synchronization. This
* is primarilly intended to control the synchronization state of
* multithreaded services. For example, telling all threads when to exit.
*
* An Event is either set or unset. If the Event is unset then it can be
* waited on for something to happen. As soon as the Event is set all
* waiting threads are released and new requests to wait are ignored until
* the Event is cleared again.
*
* Threads can also be woken up without setting the Event, which may be
* handy in certain circumstances.
*@ingroup Threading
*/
class CounterEvent
{
public:
CounterEvent() :
iCount( 0 )
{
}
~CounterEvent()
{
}
/**
* Wait indefinitely for the Event to trigger. If the event is already
* set, then return immediately. It's important to note that this may
* return at any time, not only when the Event is set, so examining the
* return value is important.
*@returns the set status of the Event.
*/
int wait()
{
cBlock.lock();
if( iCount == 0 )
{
cBlock.unlock();
return iCount;
}
cBlock.wait();
int iRet = iCount;
cBlock.unlock();
return iRet;
}
/**
* Wait for up to nSec seconds and nUSec nanoseconds for the event to
* trigger. If the Event is already set then return immediately.
*@returns the set status of the Event.
*/
int wait( int nSec, int nUSec )
{
cBlock.lock();
if( iCount == 0 )
{
cBlock.unlock();
return iCount;
}
cBlock.wait( nSec, nUSec );
bool iRet = iCount;
cBlock.unlock();
return iRet;
}
/**
* Allow one of the waiting threads to unlock without updating the set
* state of the Event.
*/
void unblockOne()
{
cBlock.lock();
cBlock.signal();
cBlock.unlock();
}
/**
* Allow all waiting threads to unlock and proceed without updating the
* set state of the Event.
*/
void unblockAll()
{
cBlock.lock();
cBlock.broadcast();
cBlock.unlock();
}
/**
* Find out if the Event is in the set state or not.
*@returns True if set, false otherwise.
*/
bool isZero()
{
cBlock.lock();
bool bRet = (iCount == 0);
cBlock.unlock();
return bRet;
}
/**
* Sets the Event's state to true and triggers all waiting threads.
*/
void decrement()
{
cBlock.lock();
iCount--; if( iCount < 0 ) iCount = 0;
if( iCount == 0 )
cBlock.broadcast();
cBlock.unlock();
}
void increment()
{
cBlock.lock();
iCount++;
cBlock.unlock();
}
/**
* Sets the Event's state to false. This does NOT trigger any waiting
* threads.
*/
void clear()
{
cBlock.lock();
iCount = 0;
cBlock.unlock();
}
private:
Condition cBlock; /**< The condition for blocking dequeues. */
int iCount;
};
}
#endif
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