fifo.js

A simple fifo buffer for node-buffers. Excellent for handling encapsulated binary data in a TCP/IP stream. I encountered many situations where I needed to decode an embedded packet structure from a socket stream.

Installation

As npm for Node.js:

$ npm install fifo-buffer

Example

Some console interaction:

> FIFO=require('./fifo.js')
[Function: FIFOBuffer]
> b = new FIFO()
FIFOBuffer {
  buffer: <Buffer 00 00 00 00 00 00 00 00 00 ... >,
  high: 1048576,
  tail: 0,
  head: 0 }
> b.enq(Buffer.from([1,2,3,4]))
true
> b.enq(Buffer.from([5,6,7,8]))
true
> b.deq(2)
<Buffer 01 02>
> b.deq(2)
<Buffer 03 04>
> b.deq(2)
<Buffer 05 06>
> b.deq(2)
<Buffer 07 08>
> b.deq(2)
null
> b.enq(Buffer.from([1,2,3,4]))
true
> b.peek(2)
<Buffer 01 02>
> b.peek(2)
<Buffer 01 02>
> b.peek(5)
null
> b.size
4
>

A sample interface to extract a packet within a TCP/IP stream. Assuming socket is configured to provide a buffer on "data". The encapsulated packet simply begins with a 4 byte header containing its length.

var FIFO = require('fifo-buffer');
var fifo = new FIFO();

// ... assuming socket setup and connected:
socket.on("data", (data) => {
   if (!fifo.enq(data))
      throw "No more space in FIFO!";
   let temp_buf;
   while (temp_buf = fifo.peek(4)) { // as long as there are 4 bytes in fifo (our header)
      let psize = temp_buf.readUInt32BE(); // we only deq complete packets so the first 4 bytes must be the length of the incoming packet.
      if (fifo.size < psize + 4)
         break;   // incomplete packet, try again next time we receive data.

      // EITHER remove header and give remaining packet to some handler:
      fifo.deq(4);   // trash 4 byte Header
      handleCompleteEncapsulatedPacket(fifo.deq(psize));
      // OR leave header in place:
      handleCompleteEncapsulatedPacket(fifo.deq(psize + 4));
   }
});

API

FIFOBuffer()

Initializes a new empty FIFOBuffer with the default capacity (1MByte).

FIFOBuffer(capacity)

Initializes a new empty FIFOBuffer with the given capacity.

FIFOBuffer#deq(n)

Dequeues the oldest n bytes of the FIFO buffer and returns a copy. Returns null when the buffer has less bytes available.

FIFOBuffer#enq(buffer)

Enqueues the buffer at the end and returns true when there was enough space. When the buffer is full the method returns false.

FIFOBuffer#peek(n)

Copies the oldest n bytes of the FIFO buffer. Does not change the state. Returns null when the buffer has less bytes available.

FIFOBuffer#size

Returns the current size of the FIFO.

Testing

As npm package:

$ npm test

Licence

ISC