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105 lines
3.0 KiB
Go
105 lines
3.0 KiB
Go
// Copyright GoFrame Author(https://goframe.org). All Rights Reserved.
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//
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// This Source Code Form is subject to the terms of the MIT License.
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// If a copy of the MIT was not distributed with this file,
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// You can obtain one at https://github.com/gogf/gf.
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package gtimer
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import (
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"container/heap"
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"github.com/gogf/gf/container/gtype"
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"math"
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"sync"
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)
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// priorityQueue is an abstract data type similar to a regular queue or stack data structure in which
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// each element additionally has a "priority" associated with it. In a priority queue, an element with
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// high priority is served before an element with low priority.
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// priorityQueue is based on heap structure.
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type priorityQueue struct {
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mu sync.RWMutex
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heap *priorityQueueHeap // the underlying queue items manager using heap.
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latestPriority *gtype.Int64 // latestPriority stores the most priority value of the heap, which is used to check if necessary to call the Pop of heap by Timer.
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}
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// priorityQueueHeap is a heap manager, of which the underlying `array` is a array implementing a heap structure.
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type priorityQueueHeap struct {
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array []priorityQueueItem
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}
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// priorityQueueItem stores the queue item which has a `priority` attribute to sort itself in heap.
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type priorityQueueItem struct {
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value interface{}
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priority int64
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}
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// newPriorityQueue creates and returns a priority queue.
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func newPriorityQueue() *priorityQueue {
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queue := &priorityQueue{
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heap: &priorityQueueHeap{
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array: make([]priorityQueueItem, 0),
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},
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latestPriority: gtype.NewInt64(math.MaxInt64),
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}
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heap.Init(queue.heap)
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return queue
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}
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// Len retrieves and returns the length of the queue.
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func (q *priorityQueue) Len() int {
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q.mu.RLock()
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defer q.mu.RUnlock()
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return q.heap.Len()
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}
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// LatestPriority retrieves and returns the minimum and the most priority value of the queue.
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func (q *priorityQueue) LatestPriority() int64 {
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return q.latestPriority.Val()
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}
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// Push pushes a value to the queue.
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// The `priority` specifies the priority of the value.
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// The lesser the `priority` value the higher priority of the `value`.
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func (q *priorityQueue) Push(value interface{}, priority int64) {
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q.mu.Lock()
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heap.Push(q.heap, priorityQueueItem{
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value: value,
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priority: priority,
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})
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q.mu.Unlock()
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// Update the minimum priority using atomic operation.
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for {
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latestPriority := q.latestPriority.Val()
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if priority >= latestPriority {
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break
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}
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if q.latestPriority.Cas(latestPriority, priority) {
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break
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}
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}
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}
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// Pop retrieves, removes and returns the most high priority value from the queue.
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func (q *priorityQueue) Pop() interface{} {
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q.mu.Lock()
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if v := heap.Pop(q.heap); v != nil {
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item := v.(priorityQueueItem)
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q.mu.Unlock()
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// Update the minimum priority using atomic operation.
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for {
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latestPriority := q.latestPriority.Val()
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if item.priority >= latestPriority {
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break
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}
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if q.latestPriority.Cas(latestPriority, item.priority) {
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break
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}
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}
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return item.value
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} else {
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q.mu.Unlock()
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}
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return nil
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}
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