FoldedArrayReverse.js

function FoldArrayRev (chunkSize) {
	this._chunkSize = chunkSize || 1000;
	this._data = [[]];
	this._tail = 0;
}
FoldArrayRev.prototype = {
	push: function (item) {
		if (this._data[this._tail].length >= this._chunkSize) {
			this._data[this._tail] = this._data[this._tail].reverse();
			this._data.push([]);
			this._tail++;
		}
		this._data[this._tail].push(item);
	} 
	, shift: function () {
		var retVal = (this._data.length > 1) ? this._data[0].pop() : this._data[0].shift();
		if (this._data[0].length < 1) {
			this._data.shift();
			this._tail--;
		}
		return(retVal);
	} 
}