cooperation/server/download.js

用于多人合作模化开发

const http = require("http");
const fs = require("fs");
const path = require("path");
const url = require("url");

const NAME = path.basename(__filename, '.js');

const mimeNames = {
    ".mp3": "audio/mpeg",
    ".mp4": "video/mp4",
    ".jpg": "image/jpeg",
    ".jpeg": "image/jpeg",
    ".png": "application/x-png",
    ".gif": "image/gif",
    ".ogg": "application/ogg",
    ".ogv": "video/ogg",
    ".oga": "audio/ogg",
    ".wav": "audio/x-wav",
    ".webm": "video/webm",
    ".html": "text/html",
    ".css": "text/css",
    ".js": "application/javascript",
    ".json": "application/json"
};

function sendResponse(response, responseStatus, responseHeaders, readable) {
    response.writeHead(responseStatus, responseHeaders);

    if (!readable)
        response.end();
    else
        readable.on("open", () => readable.pipe(response));

    return null;
}

function getMimeNameFromExt(ext) {
    let result = mimeNames[ext.toLowerCase()];

    // 最好给一个默认值
    if (!result)
        result = "application/octet-stream";
    return result;
}

function readRangeHeader(range, totalLength) {
    /*
     * Example of the method 'split' with regular expression.
     *
     * Input: bytes=100-200
     * Output: [null, 100, 200, null]
     *
     * Input: bytes=-200
     * Output: [null, null, 200, null]
     */

    if (!range || !range.length)
        return null;

    let array = range.split(/bytes=([0-9]*)-([0-9]*)/);
    let start = parseInt(array[1]);
    let end = parseInt(array[2]);
    let result = {
        Start: isNaN(start) ? 0 : start,
        End: isNaN(end) ? (totalLength - 1) : end
    };

    if (!isNaN(start) && isNaN(end)) {
        result.Start = start;
        result.End = totalLength - 1;
    }

    if (isNaN(start) && !isNaN(end)) {
        result.Start = totalLength - end;
        result.End = totalLength - 1;
    }

    return result;
}

module.exports = ({
                      port = 80,//端口
                      dir = ['/']
                  } = {}) => {
    http.createServer((request, response) => {
        //下面主要是GET类的
        // 只允许GET请求
        if (request.method !== 'GET') {
            sendResponse(response, 405, {'Allow': 'GET'}, null);
            return null;
        }

        let rqePath = url.parse(request.url, true, true).pathname.split('/').join(path.sep);
        let filename = '';

        //同步检查文件状态
        let stat = null;

        if (dir.length === 1) {
            filename = dir[0] + rqePath;
            stat =fs.statSync(filename);
            // 检查文件是否存在
            if (!stat.isFile()) {
                sendResponse(response, 404, null, null);
                return null;
            }
        } else {
            let has = false;
            dir.some(v => {
                filename = v + rqePath;
                stat =fs.statSync(filename);
                //TODO 需要优化
                if (!stat.isFile()) {
                    has = true;
                }
                return has;
            });
            if (!has) {
                sendResponse(response, 404, null, null);
                return null;
            }
        }

        let responseHeaders = {};
        let rangeRequest = readRangeHeader(request.headers['range'], stat.size);

        //不存在Range头，直接下载
        if (rangeRequest == null) {
            responseHeaders['Content-Type'] = getMimeNameFromExt(path.extname(filename));
            responseHeaders['Content-Length'] = stat.size;  // File size.
            responseHeaders['Accept-Ranges'] = 'bytes';

            //直接返回图片
            sendResponse(response, 200, responseHeaders, fs.createReadStream(filename));
            return null;
        }

        //存在Range头，分段下载
        let start = rangeRequest.Start;
        let end = rangeRequest.End;

        // If the range can't be fulfilled.
        if (start >= stat.size || end >= stat.size) {
            // Indicate the acceptable range.
            responseHeaders['Content-Range'] = 'bytes */' + stat.size; // File size.
            // Return the 416 'Requested Range Not Satisfiable'.
            sendResponse(response, 416, responseHeaders, null);
            return null;
        }

        // Indicate the current range.
        responseHeaders['Content-Range'] = 'bytes ' + start + '-' + end + '/' + stat.size;
        responseHeaders['Content-Length'] = start === end ? 0 : (end - start + 1);
        responseHeaders['Content-Type'] = getMimeNameFromExt(path.extname(filename));
        responseHeaders['Accept-Ranges'] = 'bytes';
        responseHeaders['Cache-Control'] = 'no-cache';

        // Return the 206 'Partial Content'.
        sendResponse(response, 206,
            responseHeaders, fs.createReadStream(filename, {start: start, end: end}));
    }).listen(port);
    console.log(NAME + ":监听了" + port + "端口")
};