function _fnSortingClasses(settings) {
		var oldSort = settings.aLastSort;
		var sortClass = settings.oClasses.order.position;
		var sort = _fnSortFlatten(settings);
		var features = settings.oFeatures;
		var i, ien, colIdx;

		if (features.bSort && features.bSortClasses) {
			// Remove old sorting classes
			for (i = 0, ien = oldSort.length; i < ien; i++) {
				colIdx = oldSort[i].src;

				// Remove column sorting
				$(_pluck(settings.aoData, 'anCells', colIdx))
					.removeClass(sortClass + (i < 2 ? i + 1 : 3));
			}

			// Add new column sorting
			for (i = 0, ien = sort.length; i < ien; i++) {
				colIdx = sort[i].src;

				$(_pluck(settings.aoData, 'anCells', colIdx))
					.addClass(sortClass + (i < 2 ? i + 1 : 3));
			}
		}

		settings.aLastSort = sort;
	}
Set the sorting classes on table's body, Note: it is safe to call this function
when bSort and bSortClasses are false
 @param {object} oSettings dataTables settings object
 @memberof DataTable#oApi