Node reads files in the form of data blocks

Node reads files in the form of data blocks

In Node, the default value of Transfer-Encoding in the http response header is chunked.

Transfer-Encoding: chunked

Node's inherent asynchronous mechanism allows the response to be generated gradually.

This method of sending data blocks is very efficient when I/O operations are involved. Node allows writing data to the response in the form of data blocks, and also allows reading files in the form of data blocks.

In this way, there can be efficient memory allocation. You do not need to read all the files into the memory and then respond to the customer. This saves memory when processing a large number of requests.

Var http = require ('http ');
Var fs = require ('fs ');

Http. createServer (function (req, res ){
Res. writeHead (200, {'Context-type': 'image/png '});

Var imagePath = 'd:/home.png ';

Var stream = fs. createReadStream (imagePath );

// Read data in one piece
Stream. on ('data', function (chunk ){
Res. write (chunk );
});

Stream. on ('end', function (){
Res. end ();
});

Stream. on ('error', function (){
Res. end ();
});
}). Listen (3000 );

Node also provides a more concise method pipe ()

Var http = require ('http ');
Var fs = require ('fs ');

Http. createServer (function (req, res ){
Res. writeHead (200, {'Context-type': 'image/png '});

Var imagePath = 'd:/home.png ';

Var stream = fs. createReadStream (imagePath );
Stream. pipe (res );

}). Listen (3000 );

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