node.js-Busboy实际如何工作？

Question

I'm a bit confused with Busboy module. I don't understand where it takes file data to stream as it accepts only request headers as parameter?! Take a look on example from docs:

var busboy = new Busboy({ headers: req.headers });
busboy.on('file', function (fieldname, file, filename, encoding, mimetype) {
   //...
   // btw file is ReadableStream!
});

Answer 1

它通过管道将请求主体传递给它，请参见示例 ：

req.pipe(busboy);