FUNCTIONS // 
FUNCTION: getBuffer( W )
Returns a buffer array where each element is pre-initialized to zero.

@private
@param {number} W - buffer size
@returns {array} buffer
function getBuffer( W ) {
		var buffer = new Array( W );
		for ( var i = 0; i < W; i++ ) {
			buffer[ i ] = 0;
		}
		return buffer;
	}