87 lines
2.1 KiB
Plaintext
87 lines
2.1 KiB
Plaintext
const taskPool = [] // 请求池
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let numRequest = 0 // 正在执行数量
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const maxRequest = 4 // 可配置
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let taskTimer // 轮询的定时器
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const cachedTask = {} // 存放的任务数据
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// 预加载池的添加
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function addTaskIntoPool(task) {
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return new Promise((resolve, reject) => {
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const cache = cachedTask[task.key]
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const subscribe = (executeRes) => {
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if (executeRes.success) {
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resolve(executeRes.res)
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} else {
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reject(executeRes.err)
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}
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}
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const priority = (task.priority || task.priority === 0) || 999
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if (cache) {
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cache.priority = priority
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const callbacks = cache.callbacks || []
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callbacks.push(subscribe)
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} else {
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task.callbacks = [subscribe]
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cachedTask[task.key] = task
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taskPool.push(task)
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}
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})
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}
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// 执行下载
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function executeTask() {
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if (taskPool.length > 0) {
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sortTaskPool()
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const executeRequest = maxRequest - numRequest
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if (executeRequest > 0) {
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for (let i = 0; i < executeRequest; i++) {
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const task = taskPool.shift()
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if (!task) {
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return
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}
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numRequest++
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task.execute().then((res) => {
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numRequest--
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task.callbacks && task.callbacks.map(callback => {
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callback({ success: true, res })
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})
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executeTask()
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}, (err) => {
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numRequest--
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task.callbacks && task.callbacks.map(callback => {
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callback({ success: false, err })
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})
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delete cachedTask[task.key]
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executeTask()
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})
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}
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}
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} else {
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startTaskTimer()
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}
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}
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function sortTaskPool() {
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if (taskPool.length > 0) {
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taskPool.sort((a, b) => a - b)
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}
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}
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// 轮询检查请求池中是否有请求需要执行
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function startTaskTimer() {
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taskTimer = setInterval(() => {
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if (taskPool.length > 0) {
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stopTaskTimer()
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executeTask()
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}
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}, 500)
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}
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// 停止轮询
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function stopTaskTimer() {
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clearInterval(taskTimer)
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taskTimer = null
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}
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export default {
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addTaskIntoPool,
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executeTask,
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startTaskTimer
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}
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