var fs = require("fs");
var path = require("path");
const filePath = path.resolve(__dirname, '..' + path.sep + 'upload');

module.exports = function(request, response) {
    var filename = request.query.filename;
    var oldname = request.query.oldname;
    var file = filePath + path.sep + filename;
    
    return fs.createReadStream(file);//得到文件输入流
};