elldritch / integer-queue

A fast fixed-size queue for JavaScript.

Queue

This is a fixed-size queue that is uses typed arrays to beat the native implementation in terms of speed.

Installation

npm install integer-queue, then require('integer-queue').

Usage

new Queue(size[, type])

Create a new Queue that holds size elements of type type (see typed array views). This defaults to Int32Array.

queue.enqueue(item)

Attempt to enqueue item. If the queue is full, throw a QueueException. If item cannot be represented as an instance of the Queue's type, behaviour following this action is undefined.

queue.dequeue()

Attempt to dequeue the next item. If the queue is empty, throw a QueueException.

Testing, etc.

Run npm test to run the test suite. Run grunt profile to see how this queue performs against a naive solution using native arrays. Notice that the naive solution slows dramatically past 100k elements or so (because of an optimisation trick that Node.js uses for small arrays).

Implementation details

Using an array is a bad idea, because shift re-indexes the array every time and thus a push/shift (or even worse, an unshift/pop) queue runs in linear time with respect to its length.

integer-queue's Issues

Incorrect queue fullness detection

poc

let q = new Queue(2);

q.enqueue(1);
q.enqueue(1);
q.dequeue();
q.dequeue();
q.enqueue(1); // Error: Attempted to add to full queue.

fix

if @tail - @head is @length