Node.Js之【Stream问题】

var fs = require(‘fs‘),
	path = require(‘path‘),
	out = process.stdout;

var filePath = ‘F:/IMG_0221.MOV‘;

var readStream = fs.createReadStream(filePath);
var writeStream = fs.createWriteStream(‘file.MOV‘);

var stat = fs.statSync(filePath);

var totalSize = stat.size;	
var passedLength = 0;
var lastSize = 0;
var startTime = Date.now();
	readStream.on(‘data‘, function(chunk){
		passedLength += chunk.length;				//当有数据流出，写入数据
		if(writeStream.write(chunk) == false){		//如果没有写完，暂停读取流，这样的方式可以保持读取速度快于写入速度时，保持数据不丢失。
			readStream.pause();			
		}
	});

	readStream.on(‘end‘, function(){
		writeStream.end();							//当没有数据时，关闭数据流	
	});

	writeStream.on(‘drain‘, function(){
		readStream.resume();						//写完后，继续读取数据
	});

	setTimeout(function show(){
		var percent = Math.ceil((passedLength / totalSize) * 100);
		var size = Math.ceil(passedLength / 1000000);
		var diff = size - lastSize;
			out.clearLine();
			out.cursorTo(0);
			out.write(‘已完成‘ + size + ‘MB,‘+ percent +‘%,速度：‘+ diff*2 +‘MB/s‘);
			if(passedLength < totalSize){
				setTimeout(show, 50);
			}else{
				var endTime = Date.now();
				console.log();
				console.log(‘共用时：‘ + (endTime -startTime) / 1000 + ‘秒。‘);
			}
	}, 500)