github.com/onflow/flow-go@v0.35.7-crescendo-preview.23-atree-inlining/network/queue/priorityQueue.go (about)

     1  package queue
     2  
     3  import "time"
     4  
     5  type item struct {
     6  	message  interface{}
     7  	priority int // The priority of the item in the queue.
     8  	// The index is needed by update and is maintained by the heap.Interface methods.
     9  	index     int       // The index of the item in the heap.
    10  	timestamp time.Time // timestamp to maintain insertions order for items with the same priority and for telemetry
    11  
    12  }
    13  
    14  // A priorityQueue implements heap.Interface and holds Items.
    15  type priorityQueue []*item
    16  
    17  func (pq priorityQueue) Len() int { return len(pq) }
    18  
    19  func (pq priorityQueue) Less(i, j int) bool {
    20  	// We want Pop to give us the highest, not lowest, priority so we use greater than here.
    21  	if pq[i].priority > pq[j].priority {
    22  		return true
    23  	}
    24  	if pq[i].priority < pq[j].priority {
    25  		return false
    26  	}
    27  	// if both items have the same priority, then pop the oldest
    28  	return pq[i].timestamp.Before(pq[j].timestamp)
    29  }
    30  
    31  func (pq priorityQueue) Swap(i, j int) {
    32  	pq[i], pq[j] = pq[j], pq[i]
    33  	pq[i].index = i
    34  	pq[j].index = j
    35  }
    36  
    37  func (pq *priorityQueue) Push(x interface{}) {
    38  	n := len(*pq)
    39  	item, ok := x.(*item)
    40  	if !ok {
    41  		return
    42  	}
    43  	item.index = n
    44  	*pq = append(*pq, item)
    45  }
    46  
    47  func (pq *priorityQueue) Pop() interface{} {
    48  	old := *pq
    49  	n := len(old)
    50  	item := old[n-1]
    51  	old[n-1] = nil  // avoid memory leak
    52  	item.index = -1 // for safety
    53  	*pq = old[0 : n-1]
    54  	return item
    55  }