更换下载库
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lyswhut
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import fs from 'fs'
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import path from 'path'
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import request from 'request'
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import { EventEmitter } from 'events'
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import { performance } from 'perf_hooks'
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import { STATUS } from './util'
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const defaultChunkInfo = {
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path: null,
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startByte: 0,
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endByte: '',
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}
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const defaultRequestOptions = {
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method: 'GET',
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headers: {},
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}
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const defaultOptions = {
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}
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class Task extends EventEmitter {
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/**
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*
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* @param {String} url download url
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* @param {Object} chunkInfo
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* @param {Object} options
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*/
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constructor(url, savePath, filename, options = {}) {
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super()
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this.resumeLastChunk = null
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this.downloadUrl = url
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this.chunkInfo = Object.assign({}, defaultChunkInfo, {
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path: path.join(savePath, filename),
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startByte: 0,
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})
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if (!this.chunkInfo.endByte) this.chunkInfo.endByte = ''
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this.options = Object.assign({}, defaultOptions, options)
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this.requestOptions = Object.assign({}, defaultRequestOptions, this.options.requestOptions || {})
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if (!this.requestOptions.headers) this.requestOptions.headers = {}
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this.progress = {
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total: 0,
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downloaded: 0,
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speed: 0,
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}
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this.statsEstimate = {
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time: 0,
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bytes: 0,
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prevBytes: 0,
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}
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this.status = STATUS.idle
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}
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__init() {
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this.status = STATUS.init
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const { path, startByte, endByte } = this.chunkInfo
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if (startByte) this.requestOptions.headers.range = `bytes=${startByte}-${endByte}`
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return new Promise((resolve, reject) => {
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if (!path) return resolve()
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fs.stat(path, (errStat, stats) => {
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if (errStat) {
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if (errStat.code !== 'ENOENT') {
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this.__handleError(errStat)
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reject(errStat)
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return
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}
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} else if (stats.size >= 10) {
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fs.open(path, 'r', (errOpen, fd) => {
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if (errOpen) {
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this.__handleError(errOpen)
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reject(errOpen)
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return
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}
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fs.read(fd, Buffer.alloc(10), 0, 10, stats.size - 10, (errRead, bytesRead, buffer) => {
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if (errRead) {
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this.__handleError(errRead)
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reject(errRead)
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return
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}
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fs.close(fd, errClose => {
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if (errClose) {
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this.__handleError(errClose)
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reject(errClose)
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return
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}
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// resume download
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// console.log(buffer)
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this.resumeLastChunk = buffer
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this.progress.downloaded = stats.size
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this.requestOptions.headers.range = `bytes=${stats.size - 10}-${endByte || ''}`
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resolve()
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})
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})
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})
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return
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}
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resolve()
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})
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})
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}
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__httpFetch(url, options) {
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// console.log(options)
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this.request = request(url, options)
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.on('response', response => {
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if (response.statusCode !== 200 && response.statusCode !== 206) {
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this.status = STATUS.failed
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this.emit('fail', response)
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this.__closeRequest()
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this.__closeWriteStream()
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return
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}
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this.emit('response', response)
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try {
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this.__initDownload(response)
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} catch (error) {
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return this.__handleError(error)
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}
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this.status = STATUS.running
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response
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.on('data', this.__handleWriteData.bind(this))
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.on('error', err => this.__handleError(err))
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.on('end', () => this.__handleComplete())
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})
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.on('error', err => this.__handleError(err))
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.on('close', () => this.__closeWriteStream())
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}
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__initDownload(response) {
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this.progress.total = parseInt(response.headers['content-length'] || 0)
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let options = {}
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let isResumable = this.options.forceResume || response.headers['accept-ranges'] !== 'none'
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if (isResumable) {
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options.flags = 'a'
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if (this.progress.downloaded) this.progress.total -= 10
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} else {
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if (this.chunkInfo.startByte > 0) return this.__handleError(new Error('The resource cannot be resumed download.'))
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}
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this.progress.total += this.progress.downloaded
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this.statsEstimate.prevBytes = this.progress.downloaded
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if (!this.chunkInfo.path) return this.__handleError(new Error('Chunk save Path is not set.'))
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this.ws = fs.createWriteStream(this.chunkInfo.path, options)
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this.ws.on('finish', () => this.__closeWriteStream())
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this.ws.on('error', async err => {
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await this.__handleError(err)
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fs.unlink(this.chunkInfo.path, () => this.__handleError(err))
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})
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}
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__handleComplete() {
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if (this.status == STATUS.error) return
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this.__closeWriteStream().then(() => {
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if (this.progress.downloaded == this.progress.total) {
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this.status = STATUS.completed
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this.emit('completed')
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} else {
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this.status = STATUS.stopped
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this.emit('stop')
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}
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})
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console.log('end')
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}
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__handleError(error) {
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if (this.status == STATUS.error) return
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this.status = STATUS.error
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this.__closeRequest()
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this.__closeWriteStream()
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this.emit('error', error)
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}
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__closeWriteStream() {
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return new Promise((resolve, reject) => {
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if (!this.ws) return resolve()
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console.log('close write stream')
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this.ws.close(err => {
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if (err) {
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this.status = STATUS.error
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this.emit('error', err)
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reject(err)
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return
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}
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this.ws = null
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resolve()
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})
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})
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}
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__closeRequest() {
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if (!this.request) return
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console.log('close request')
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this.request.abort()
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this.request = null
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}
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__handleWriteData(chunk) {
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if (this.resumeLastChunk) {
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chunk = this.__handleDiffChunk(chunk)
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if (!chunk) {
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this.__handleError(new Error('Resume failed, response chunk does not match.'))
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this.stop()
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return
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}
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}
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// console.log('data', chunk)
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if (this.status == STATUS.stopped || this.ws == null) return console.log('cancel write')
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this.__calculateProgress(chunk.length)
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this.ws.write(chunk, err => {
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if (!err) return
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console.log(err)
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this.__handleError(err)
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this.stop()
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})
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}
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__handleDiffChunk(chunk) {
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// console.log('diff', chunk)
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let resumeLastChunkLen = this.resumeLastChunk.length
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let chunkLen = chunk.length
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let isOk
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if (chunkLen >= resumeLastChunkLen) {
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isOk = chunk.slice(0, resumeLastChunkLen).toString('hex') === this.resumeLastChunk.toString('hex')
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if (!isOk) return null
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this.resumeLastChunk = null
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return chunk.slice(resumeLastChunkLen)
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} else {
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isOk = chunk.slice(0, chunkLen).toString('hex') === this.resumeLastChunk.slice(0, chunkLen).toString('hex')
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if (!isOk) return null
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this.resumeLastChunk = this.resumeLastChunk.slice(chunkLen)
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return chunk.slice(chunkLen)
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}
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}
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__handleStop() {
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return new Promise((resolve, reject) => {
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if (this.request) {
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this.request.abort()
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this.request = null
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}
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if (this.ws) {
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this.ws.close(err => {
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if (err) {
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reject(err)
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this.emit('error', err)
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return
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}
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this.ws = null
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resolve()
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})
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} else {
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resolve()
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}
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})
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}
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__calculateProgress(receivedBytes) {
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const currentTime = performance.now()
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const elaspsedTime = currentTime - this.statsEstimate.time
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const progress = this.progress
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progress.downloaded += receivedBytes
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progress.progress = progress.total ? (progress.downloaded / progress.total) * 100 : -1
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// emit the progress every second or if finished
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if (progress.downloaded === progress.total || elaspsedTime > 1000) {
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this.statsEstimate.time = currentTime
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this.statsEstimate.bytes = progress.downloaded - this.statsEstimate.prevBytes
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this.statsEstimate.prevBytes = progress.downloaded
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this.emit('progress', {
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total: progress.total,
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downloaded: progress.downloaded,
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progress: progress.progress,
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speed: this.statsEstimate.bytes,
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})
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}
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}
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async start() {
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this.status = STATUS.running
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await this.__init()
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this.__httpFetch(this.downloadUrl, this.requestOptions)
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this.emit('start')
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}
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async stop() {
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if (this.status === STATUS.stopped) return
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this.status = STATUS.stopped
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await this.__handleStop()
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this.emit('stop')
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}
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refreshUrl(url) {
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this.downloadUrl = url
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}
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}
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export default Task
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