Converting a number in javascript to a 4 byte array

Question

I'm taking my shot at writing a node server in which I need to send a 32 bit integer to a c# client (as the header).

I'm not quite sure how to do that, as the bit shift operators confuse me. I think my c# client expects these integers in little endian format (I'm not sure, I say that because the NetworkStream IsLittleEndian property is true).

So say I have a variable in javascript that's something like

var packetToDeliverInBytes = GetByteArrayOfSomeData();

//get the integer we need to turn into 4 bytes
var sizeOfPacket = packetToDeliver.length;

//this is what I don't know how to do
var bytes = ConvertNumberTo4Bytes(sizeOfPacket)

//then somehow do an operation that combines these two byte arrays together
//(bytes and packetToDeliverInBytes in this example)
//so the resulting byte array would be (packetToLiver.length + 4) bytes in size

//then send the bytes away to the client
socket.write(myByteArray);

How do I write the ConvertNumberTo4Bytes() function?

Bonus

How do I combine these 2 byte arrays into one so I can send them in one socket.write call

See if this helps: nodejs.org/api/…

elclanrs
– elclanrs

2013-07-01 00:26:30 +00:00
Commented Jul 1, 2013 at 0:26 — elclanrs
– elclanrs, Commented Jul 1, 2013 at 0:26

Kyle Gobel · Accepted Answer · 2013-07-01 04:58:20Z

1

Using the Buffer object in node seems to be the way to go thanks to elclanrs comment.

var buf = new Buffer(4 + sizeOfPacket);
buf.writeInt32LE(sizeOfPacket, 0);
buf.write(packetToDeliverInBytes, 4);

socket.write(buf);

answered Jul 1, 2013 at 4:58

Kyle Gobel

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