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
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.