user-extensions-resume.js

"use strict";

/*
The TFTP doesn't have any built-in mechanism for resuming a transfer, however,
with the user extensions it is possible. This example uses the extension
"offset". Only GET requests are allowed.
*/

var fs = require ("fs");
var tftp = require ("../lib");

var handleError = function (error){
	console.error (error);
};

var server = tftp.createServer ({ denyPUT: true }, function (req, res){
	var offset = 0;
	if (req.stats.userExtensions.offset !== undefined){
		offset = ~~req.stats.userExtensions.offset;
		if (offset < 0){
			return req.abort ("The offset must be a positive integer");
		}
	}
	
	var file = this.root + "/" + req.file;
	var abortError;
	
	req.on ("error", function (error){
		rs.destroy ();
		handleError (error);
	});
	req.on ("abort", function (){
		handleError (abortError);
	});
	
	var rs = fs.createReadStream (file, { start: offset })
			.on ("error", function (error){
				abortError = error;
				req.abort (tftp.EIO);
			});
	
	fs.stat (file, function (error, stats){
		if (error){
			abortError = error;
			return req.abort (tftp.EIO);
		}
		
		var size = stats.size  - offset;
		res.setSize (size < 0 ? 0 : size);
		rs.pipe (res);
	});
});

server.on ("error", function (error){
	console.error (error);
});

server.on ("listening", doRequest);

server.listen ();

function doRequest (){
	var clean = function (){
		server.close ();
		try{ fs.unlinkSync ("tmp1"); }catch (error){}
		try{ fs.unlinkSync ("tmp2"); }catch (error){}
	};

	fs.writeFileSync ("tmp1", "0123456789");
	fs.writeFileSync ("tmp2", "01234");

	var client = tftp.createClient ();

	//Get the content "56789" from tmp1 and append it to tmp2 which contains
	//"01234"
	var gs = client.createGetStream ("tmp1", { userExtensions: { offset: 5 } })
			.on ("error", function (error){
				console.error (error);
				clean ();
			});
				
	var ws = fs.createWriteStream ("tmp2", { flags: "a" })
			.on ("error", function (error){
				console.error (error);
				gs.abort (tftp.EIO);
				clean ();
			})
			.on ("finish", function (){
				console.log (fs.readFileSync ("tmp2", { encoding: "utf8" }));
				//0123456789
				clean ();
			});

	gs.pipe (ws);
};