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/*
* Copyright (C) 2007-2013 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_SYNCHRO_QUEUE_H
#define BU_SYNCHRO_QUEUE_H
#include <pthread.h>
#include "bu/mutex.h"
#include "bu/condition.h"
namespace Bu
{
/**
* A thread-safe queue class. This class is a very simple queue with some
* cool extra functionality for use with the Synchro system. The main extra
* that it provides is the option to either dequeue without blocking, with
* infinite blocking, or with timed blocking, which will return a value if
* something is enqueued within the specified time limit, or NULL if the
* time limit is exceded.
*@ingroup Threading Containers
*/
template <class T>
class SynchroQueue
{
private:
/**
* Helper struct. Keeps track of linked-list items for the queue data.
*/
typedef struct Item
{
T pData;
Item *pNext;
} Item;
public:
/**
* Construct an empty queue.
*/
SynchroQueue() :
pStart( NULL ),
pEnd( NULL ),
nSize( 0 )
{
}
/**
* Destroy the queue. This function will simply free all contained
* structures. If you stored pointers in the queue, this will lose the
* pointers without cleaning up the memory they pointed to. Make sure
* you're queue is empty before allowing it to be destroyed!
*/
~SynchroQueue()
{
cBlock.lock();
Item *pCur = pStart;
while( pCur )
{
Item *pTmp = pCur->pNext;
delete pCur;
pCur = pTmp;
}
cBlock.unlock();
}
/**
* Enqueue a pieces of data. The new data will go at the end of the
* queue, and unless another piece of data is enqueued, will be the
* last piece of data to be dequeued.
*@param pData The data to enqueue. If this is not a primitive data
* type it's probably best to use a pointer type.
*/
void enqueue( T pData )
{
cBlock.lock();
if( pStart == NULL )
{
pStart = pEnd = new Item;
pStart->pData = pData;
pStart->pNext = NULL;
nSize++;
}
else
{
pEnd->pNext = new Item;
pEnd = pEnd->pNext;
pEnd->pData = pData;
pEnd->pNext = NULL;
nSize++;
}
cBlock.signal();
cBlock.unlock();
}
/**
* Dequeue the first item from the queue. This function can operate in
* two different modes, blocking and non-blocking. In non-blocking
* mode it will return immediately weather there was data in the queue
* or not. If there was data it will remove it from the queue and
* return it to the caller.
*
* In blocking mode it will block forever wating for data to be
* enqueued. When data finally is enqueued this function will return
* immediately with the new data. The only way this function should
* ever return a null in blocking mode is if the calling thread was
* cancelled. It's probably a good idea to check for NULL return
* values even if you use blocking, just to be on the safe side.
*@param bBlock Set to true to enable blocking, leave as false to work
* in non-blocking mode.
*@returns The next piece of data in the queue, or NULL if no data was
* in the queue.
*/
T dequeue( bool bBlock=false )
{
cBlock.lock();
if( pStart == NULL )
{
if( bBlock )
{
cBlock.wait();
if( pStart == NULL )
{
cBlock.unlock();
return NULL;
}
T pTmp = pStart->pData;
Item *pDel = pStart;
pStart = pStart->pNext;
delete pDel;
nSize--;
cBlock.unlock();
return pTmp;
}
cBlock.unlock();
return NULL;
}
else
{
T pTmp = pStart->pData;
Item *pDel = pStart;
pStart = pStart->pNext;
delete pDel;
nSize--;
cBlock.unlock();
return pTmp;
}
}
/**
* Operates just like the other dequeue function in blocking mode with
* one twist. This function will block for at most nSec seconds and
* nUSec micro-seconds. If the timer is up and no data is available,
* this will just return NULL. If data is enqueued before the timeout
* expires, it will dequeue and exit immediately.
*@param nSec The number of seconds to wait, max.
*@param nUSec The number of micro-seconds to wait, max.
*@returns The next piece of data in the queue, or NULL if the timeout
* was exceeded.
*/
T dequeue( int nSec, int nUSec )
{
cBlock.lock();
if( pStart == NULL )
{
cBlock.wait( nSec, nUSec );
if( pStart == NULL )
{
cBlock.unlock();
return NULL;
}
T pTmp = pStart->pData;
Item *pDel = pStart;
pStart = pStart->pNext;
delete pDel;
nSize--;
cBlock.unlock();
return pTmp;
}
else
{
T pTmp = pStart->pData;
Item *pDel = pStart;
pStart = pStart->pNext;
delete pDel;
nSize--;
cBlock.unlock();
return pTmp;
}
}
/**
* Checks to see if the queue has data in it or not. Note that there
* is no function to determine the length of the queue. This data
* isn't kept track of. If you really need to know, fix this.
*@returns True if the queue is empty, false if it has data in it.
*/
bool isEmpty()
{
cBlock.lock();
bool bEmpty = (pStart == NULL );
cBlock.unlock();
return bEmpty;
}
long getSize()
{
cBlock.lock();
long nRet = nSize;
cBlock.unlock();
return nRet;
}
void unblockAll()
{
cBlock.lock();
cBlock.broadcast();
cBlock.unlock();
}
private:
Item *pStart; /**< The start of the queue, the next element to dequeue. */
Item *pEnd; /**< The end of the queue, the last element to dequeue. */
long nSize; /**< The number of items in the queue. */
Condition cBlock; /**< The condition for blocking dequeues. */
};
}
#endif
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