function iterUnshift( iterator ) {
	var items;
	var iter;
	var FLG;
	var i;
	if ( !isIteratorLike( iterator ) ) {
		throw new TypeError( format( 'invalid argument. First argument must be an iterator protocol-compliant object. Value: `%s`.', iterator ) );
	}
	items = [];
	for ( i = 1; i < arguments.length; i++ ) {
		items.push( arguments[ i ] );
	}
	FLG = 0;
	i = -1;

	// Create an iterator protocol-compliant object:
	iter = {};
	setReadOnly( iter, 'next', next );
	setReadOnly( iter, 'return', end );

	// If an environment supports `Symbol.iterator`, make the iterator iterable:
	if ( iteratorSymbol && isFunction( iterator[ iteratorSymbol ] ) ) {
		setReadOnly( iter, iteratorSymbol, factory );
	}
	return iter;

	/**
	* Returns an iterator protocol-compliant object containing the next iterated value.
	*
	* @private
	* @returns {Object} iterator protocol-compliant object
	*/
	function next() {
		var v;
		if ( FLG === 2 ) {
			return {
				'done': true
			};
		}
		if ( FLG === 1 ) {
			v = iterator.next();
			if ( v.done ) {
				FLG = 2;
			}
			return v;
		}
		i += 1;
		if ( i >= items.length ) {
			FLG = 1;
			return next();
		}
		return {
			'value': items[ i ],
			'done': false
		};
	}

	/**
	* Finishes an iterator.
	*
	* @private
	* @param {*} [value] - value to return
	* @returns {Object} iterator protocol-compliant object
	*/
	function end( value ) {
		FLG = 2;
		if ( arguments.length ) {
			return {
				'value': value,
				'done': true
			};
		}
		return {
			'done': true
		};
	}

	/**
	* Returns a new iterator.
	*
	* @private
	* @returns {Iterator} iterator
	*/
	function factory() {
		var args;
		var i;

		args = [ iterator[ iteratorSymbol ]() ];
		for ( i = 0; i < items.length; i++ ) {
			args.push( items[ i ] );
		}
		return iterUnshift.apply( null, args );
	}
}
Returns an iterator which prepends values to the beginning of a provided iterator.

@param {Iterator} iterator - input iterator
@param {*} items - values to prepend
@throws {TypeError} first argument must be an iterator protocol-compliant object
@returns {Iterator} iterator

@example
var array2iterator = require( '@stdlib/array/to-iterator' );

var iter = iterUnshift( array2iterator( [ 1, 2 ] ), 3, 4 );

var v = iter.next().value;
// returns 3

v = iter.next().value;
// returns 4

v = iter.next().value;
// returns 1

v = iter.next().value;
// returns 2

var bool = iter.next().done;
// returns true