protected function getMappedChunk( array &$data, array $mapping )
	{
		$idx = 0;
		$map = [];

		foreach( $mapping as $pos => $key )
		{
			if( isset( $map[$idx][$key] ) ) {
				$idx++;
			}

			if( isset( $data[$pos] ) )
			{
				$map[$idx][$key] = $data[$pos];
				unset( $data[$pos] );
			}
		}

		return $map;
	}