这就是我最终做到的方式。背后的想法是创建实现ReadStream接口的可读流，然后使用
pipe()方法将数据通过管道传输到可写流。
var fs = require('fs');var writeStream = fs.createWriteStream('someFile.txt', { flags : 'w' });var readStream = new MyReadStream();readStream.pipe(writeStream);writeStream.on('close', function () { console.log('All done!');});MyReadStream可以从猫鼬QueryStream中获取类的示例。
