node.js异步实现大文件copy

node.js异步实现大文件copy

node.js异步实现大文件copy
/*
    大文件复制实例
*/
var fs = require('fs');
var path = require('path');
var out = process.stdout;
 
function maxCopy(srcPath, destPath) {
 
    //读入文件流
    var readStream = fs.createReadStream(srcPath);
    //写入文件流
    var writeStream = fs.createWriteStream(destPath);
    //文件类型，大小等信息
    var stat = fs.statSync(srcPath);
    var totalSize = stat.size;
    var passedLength = 0;
    var lastSize = 0;
    var startTime = Date.now();
 
    readStream.on('data', function (chunk) {
        passedLength += chunk.length;
        if (writeStream.write(chunk) === false) {
            readStream.pause();
        }
    });
 
    //流读取结束
    readStream.on('end', function () {
        writeStream.end();
    });
 
    //流写入成功，则唤醒读取流
    writeStream.on('drain', function () {
        readStream.resume();
    });
 
    setTimeout(function show() {
        var percent = Math.ceil((passedLength / totalSize) * 100);
        var size = Math.ceil(passedLength / 1000000);
        var diff = size - lastSize;
        lastSize = size;
        out.clearLine();
        out.cursorTo(0);
        out.write('已完成' + size + 'MB, ' + percent + '%, 速度：' + diff * 2 + 'MB/s');
        if (passedLength < totalSize) {
            setTimeout(show, 500);
        } else {
            var endTime = Date.now();
            console.log();
            console.log('共用时：' + (endTime - startTime) / 1000 + '秒。');
        }
    }, 500);
 
}
 
maxCopy('D:\\temp\\20150727升级包.rar','d:\\a.rar');