/**
* Changes the priority of the element at the specified position of the
* priority queue, maintaining the heap condition of the queue.
*
* This function has a time complexity of O(Log N),
* with N being the number of elements in the queue.
*
* @return int rc >= 0: The index of the element after the priority change.
* @return int rc < 0: An error see pbl_errno:
*
* <BR>PBL_ERROR_OUT_OF_BOUNDS - Index is out of range (index < 0 || index >= size()).
*/
int pblPriorityQueueChangePriorityAt( /* */
PblPriorityQueue * queue, /** The queue to use */
int index, /** The index at which the priority is to be changed */
int priority /** The new priority of the element */
)
{
PblPriorityQueueEntry *entry =
(PblPriorityQueueEntry *)pblHeapGet( (PblHeap *)queue, index );
if( entry == (PblPriorityQueueEntry *)-1 )
{
return -1;
}
if( priority < entry->priority )
{
int size = pblHeapSize( (PblHeap *)queue );
entry->priority = priority;
// For zero based arrays all entries with an index bigger
// than 'size / 2 - 1' do not have any children.
//
// Decreasing the priority cannot violate the heap condition
// for entries with no children
//
if( index <= size / 2 - 1 )
{
// The heap condition only needs to be ensured
// if the entry has children
//
return pblHeapEnsureCondition( queue, index );
}
}
else if( priority > entry->priority )
{
entry->priority = priority;
// Increasing the priority cannot violate the heap condition
// for the top entry at index 0
//
if( index > 0 )
{
// The heap condition needs to ensured
//
return pblHeapEnsureCondition( queue, index );
}
}
return index;
}
/**
* Inserts the element with the specified priority into the
* priority queue and maintains the heap condition
* of the priority queue.
*
* This function has a time complexity of O(Log N),
* with N being the number of elements in the queue.
*
* @return int rc >= 0: The size of the queue.
* @return int rc < 0: An error, see pbl_errno:
*
* <BR>PBL_ERROR_OUT_OF_MEMORY - Out of memory.
*/
int pblPriorityQueueInsert( /* */
PblPriorityQueue * queue, /** The queue to use */
int priority, /** Priority of the element to be inserted */
void * element /** Element to be inserted to the queue */
)
{
// Add to the end of the queue
//
int rc = pblPriorityQueueAddLast(queue, priority, element);
if (rc > 1)
{
// Ensure the heap condition for the last entry
//
pblHeapEnsureCondition(queue, rc - 1);
}
return rc;
}
