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ChuXun
333
js/m3u8.downloader.js
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333
js/m3u8.downloader.js
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class Downloader {
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constructor(fragments = [], thread = 6) {
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this.fragments = fragments; // 切片列表
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this.allFragments = fragments; // 储存所有原始切片列表
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this.thread = thread; // 线程数
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this.events = {}; // events
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this.decrypt = null; // 解密函数
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this.transcode = null; // 转码函数
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this.init();
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}
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/**
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* 初始化所有变量
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*/
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init() {
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this.index = 0; // 当前任务索引
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this.buffer = []; // 储存的buffer
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this.state = 'waiting'; // 下载器状态 waiting running done abort
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this.success = 0; // 成功下载数量
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this.errorList = new Set(); // 下载错误的列表
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this.buffersize = 0; // 已下载buffer大小
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this.duration = 0; // 已下载时长
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this.pushIndex = 0; // 推送顺序下载索引
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this.controller = []; // 储存中断控制器
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this.running = 0; // 正在下载数量
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}
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/**
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* 设置监听
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* @param {string} eventName 监听名
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* @param {Function} callBack
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*/
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on(eventName, callBack) {
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if (this.events[eventName]) {
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this.events[eventName].push(callBack);
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} else {
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this.events[eventName] = [callBack];
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}
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}
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/**
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* 触发监听器
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* @param {string} eventName 监听名
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* @param {...any} args
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*/
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emit(eventName, ...args) {
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if (this.events[eventName]) {
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this.events[eventName].forEach(callBack => {
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callBack(...args);
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});
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}
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}
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/**
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* 设定解密函数
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* @param {Function} callback
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*/
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setDecrypt(callback) {
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this.decrypt = callback;
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}
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/**
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* 设定转码函数
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* @param {Function} callback
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*/
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setTranscode(callback) {
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this.transcode = callback;
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}
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/**
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* 停止下载 没有目标 停止所有线程
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* @param {number} index 停止下载目标
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*/
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stop(index = undefined) {
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if (index !== undefined) {
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this.controller[index] && this.controller[index].abort();
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return;
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}
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this.controller.forEach(controller => { controller.abort() });
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this.state = 'abort';
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}
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/**
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* 检查对象是否错误列表内
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* @param {object} fragment 切片对象
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* @returns {boolean}
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*/
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isErrorItem(fragment) {
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return this.errorList.has(fragment);
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}
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/**
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* 返回所有错误列表
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*/
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get errorItem() {
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return this.errorList;
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}
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/**
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* 按照顺序推送buffer数据
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*/
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sequentialPush() {
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if (!this.events["sequentialPush"]) { return; }
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for (; this.pushIndex < this.fragments.length; this.pushIndex++) {
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if (this.buffer[this.pushIndex]) {
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this.emit('sequentialPush', this.buffer[this.pushIndex]);
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delete this.buffer[this.pushIndex];
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continue;
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}
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break;
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}
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}
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/**
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* 限定下载范围
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* @param {number} start 下载范围 开始索引
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* @param {number} end 下载范围 结束索引
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* @returns {boolean}
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*/
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range(start = 0, end = this.fragments.length) {
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if (start > end) {
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this.emit('error', 'start > end');
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return false;
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}
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if (end > this.fragments.length) {
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this.emit('error', 'end > total');
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return false;
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}
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if (start >= this.fragments.length) {
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this.emit('error', 'start >= total');
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return false;
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}
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if (start != 0 || end != this.fragments.length) {
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this.fragments = this.fragments.slice(start, end);
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// 更改过下载范围 重新设定index
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this.fragments.forEach((fragment, index) => {
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fragment.index = index;
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});
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}
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// 总数为空 抛出错误
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if (this.fragments.length == 0) {
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this.emit('error', 'List is empty');
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return false;
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}
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return true;
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}
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/**
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* 获取切片总数量
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* @returns {number}
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*/
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get total() {
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return this.fragments.length;
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}
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/**
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* 获取切片总时间
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* @returns {number}
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*/
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get totalDuration() {
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return this.fragments.reduce((total, fragment) => total + fragment.duration, 0);
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}
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/**
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* 切片对象数组的 setter getter
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*/
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set fragments(fragments) {
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// 增加index参数 为多线程异步下载 根据index属性顺序保存
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this._fragments = fragments.map((fragment, index) => ({ ...fragment, index }));
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}
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get fragments() {
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return this._fragments;
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}
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/**
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* 获取 #EXT-X-MAP 标签的文件url
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* @returns {string}
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*/
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get mapTag() {
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if (this.fragments[0].initSegment && this.fragments[0].initSegment.url) {
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return this.fragments[0].initSegment.url;
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}
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return "";
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}
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/**
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* 添加一条新资源
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* @param {Object} fragment
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*/
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push(fragment) {
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fragment.index = this.fragments.length;
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this.fragments.push(fragment);
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}
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/**
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* 下载器 使用fetch下载文件
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* @param {object} fragment 重新下载的对象
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*/
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downloader(fragment = null) {
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if (this.state === 'abort') { return; }
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// 是否直接下载对象
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const directDownload = !!fragment;
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// 非直接下载对象 从this.fragments获取下一条资源 若不存在跳出
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if (!directDownload && !this.fragments[this.index]) { return; }
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// fragment是数字 直接从this.fragments获取
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if (typeof fragment === 'number') {
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fragment = this.fragments[fragment];
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}
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// 不存在下载对象 从提取fragments
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fragment ??= this.fragments[this.index++];
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this.state = 'running';
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this.running++;
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// 资源已下载 跳过
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// if (this.buffer[fragment.index]) { return; }
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// 停止下载控制器
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const controller = new AbortController();
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this.controller[fragment.index] = controller;
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const options = { signal: controller.signal };
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// 下载前触发事件
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this.emit('start', fragment, options);
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// 开始下载
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fetch(fragment.url, options)
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.then(response => {
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if (!response.ok) {
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throw new Error(response.status, { cause: 'HTTPError' });
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}
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const reader = response.body.getReader();
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const contentLength = parseInt(response.headers.get('content-length')) || 0;
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fragment.contentType = response.headers.get('content-type') ?? 'null';
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let receivedLength = 0;
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const chunks = [];
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const pump = async () => {
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while (true) {
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const { value, done } = await reader.read();
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if (done) { break; }
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// 流式下载
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fragment.fileStream ? fragment.fileStream.write(new Uint8Array(value)) : chunks.push(value);
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receivedLength += value.length;
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this.emit('itemProgress', fragment, false, receivedLength, contentLength, value);
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}
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if (fragment.fileStream) {
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return new ArrayBuffer();
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}
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const allChunks = new Uint8Array(receivedLength);
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let position = 0;
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for (const chunk of chunks) {
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allChunks.set(chunk, position);
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position += chunk.length;
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}
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this.emit('itemProgress', fragment, true);
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return allChunks.buffer;
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}
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return pump();
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})
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.then(buffer => {
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this.emit('rawBuffer', buffer, fragment);
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// 存在解密函数 调用解密函数 否则直接返回buffer
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return this.decrypt ? this.decrypt(buffer, fragment) : buffer;
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})
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.then(buffer => {
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this.emit('decryptedData', buffer, fragment);
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// 存在转码函数 调用转码函数 否则直接返回buffer
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return this.transcode ? this.transcode(buffer, fragment) : buffer;
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})
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.then(buffer => {
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// 储存解密/转码后的buffer
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this.buffer[fragment.index] = buffer;
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// 成功数+1 累计buffer大小和视频时长
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this.success++;
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this.buffersize += buffer.byteLength;
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this.duration += fragment.duration ?? 0;
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// 下载对象来自错误列表 从错误列表内删除
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this.errorList.has(fragment) && this.errorList.delete(fragment);
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// 推送顺序下载
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this.sequentialPush();
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this.emit('completed', buffer, fragment);
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// 下载完成
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if (this.success == this.fragments.length) {
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this.state = 'done';
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this.emit('allCompleted', this.buffer, this.fragments);
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}
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}).catch((error) => {
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console.log(error);
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if (error.name == 'AbortError') {
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this.emit('stop', fragment, error);
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return;
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}
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this.emit('downloadError', fragment, error);
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// 储存下载错误切片
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!this.errorList.has(fragment) && this.errorList.add(fragment);
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}).finally(() => {
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this.running--;
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// 下载下一个切片
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if (!directDownload && this.index < this.fragments.length) {
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this.downloader();
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}
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});
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}
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/**
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* 开始下载 准备数据 调用下载器
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* @param {number} start 下载范围 开始索引
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* @param {number} end 下载范围 结束索引
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*/
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start(start = 0, end = this.fragments.length) {
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// 检查下载器状态
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if (this.state == 'running') {
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this.emit('error', 'state running');
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return;
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}
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// 从下载范围内 切出需要下载的部分
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if (!this.range(start, end)) {
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return;
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}
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// 初始化变量
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this.init();
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// 开始下载 多少线程开启多少个下载器
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for (let i = 0; i < this.thread && i < this.fragments.length; i++) {
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this.downloader();
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}
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}
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/**
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* 销毁 初始化所有变量
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*/
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destroy() {
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this.stop();
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this._fragments = [];
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this.allFragments = [];
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this.thread = 6;
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this.events = {};
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this.decrypt = null;
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this.transcode = null;
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this.init();
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}
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}
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