circular-buffer

NodeJS Circular Buffer

This is a simple circular buffer implementation for NodeJS.

The implementation can function both as a forgetful queue (which it's most suited for), and as a (forgetful) stack. Queue functionality uses enq() and deq(); stack functionality uses push() and pop(). Values are enqueued at the front of the buffer and dequeued at the back of the buffer; pushing and popping is at the back of the buffer. Indexing is front-to-back: the last-enqueued item has lowest index, which is also the first-pushed item.

Usage

Below is a sample session with a circular buffer with this package. It should answer most questions.

var CircularBuffer = require("circular-buffer");
 
var buf = new CircularBuffer(3);
console.log(buf.capacity()); // -> 3
buf.enq(1);
buf.enq(2);
console.log(buf.size()); // -> 2
buf.toarray(); // -> [2,1]
buf.push(3);
buf.toarray(); // -> [2,1,3]
buf.enq(4);
console.log(buf.size()); // -> 3  (despite having added a fourth item!)
buf.toarray(); // -> [4,2,1]
buf.get(0); // -> 4  (last enqueued item is at start of buffer)
buf.get(0,2); // -> [4,2,1]  (2-parameter get takes start and end)
buf.toarray(); // -> [4,2,1]  (equivalent to buf.get(0,buf.size() - 1) )
console.log(buf.deq()); // -> 1
buf.toarray(); // -> [4,2]
buf.pop(); // -> 2  (deq and pop are functionally the same)
buf.deq(); // -> 4
buf.toarray(); // -> []
buf.deq(); // -> throws RangeError("CircularBuffer dequeue on empty buffer")

Functions

• size() -> integer
  • Returns the current number of items in the buffer.
• capacity() -> integer
  • Returns the maximum number of items in the buffer (specified when creating it).
• enq(value)
  • Enqueue value at the front of the buffer
• deq() -> value
  • Dequeue an item from the back of the buffer; returns that item. Throws RangeError if the buffer is empty on invocation.
• push(value)
  • Push value at the back of the buffer
• pop() -> value
  • Equivalent to deq().
• shift() -> value
  • Removes an item from the front of the buffer; returns that item. Throws RangeError if the buffer is empty on invocation.
• get(idx) -> value
  • Get the value at index idx. 0 is the front of the buffer (last-enqueued item, or first-pushed item), buf.size()-1 is the back of the buffer.
• get(start,end) -> [value]
  • Gets the values from index start up to and including index end; returns an array, in front-to-back order. Equivalent to [buf.get(start),buf.get(start+1),/*etc*/,buf.get(end)].
• toarray() -> [value]
  • Equivalent to buf.get(0,buf.size() - 1): exports all items in the buffer in front-to-back order.

Testing

To test the package simply run npm update && npm test in the package's root folder.