在nodejs中如何实现大文件读取

var fs = require('fs'); 

function readBigFileEntry(filename, response) { 
path.exists(filename, function(exists) { 
if (!filename || !exists) { 
response.writeHead(404); 
response.end(); 
return; 
} 

var readStream = fs.ReadStream(filename); 

var contentType = 'none'; 
var ext = path.extname(filename); 
switch (ext) { 
case ".flv": 
contentType = "video/flv"; 
break; 
} 

response.writeHead(200, { 
'Content-Type' : contentType, 
'Accept-Ranges' : 'bytes', 
'Server' : 'Microsoft-IIS/7.5', 
'X-Powered-By' : 'ASP.NET' 
}); 



readStream.on('close', function() { 
response.end(); 
console.log("Stream finished."); 
}); 
readStream.pipe(response); 
}); 
}