Function detect_stl_format 

pub fn detect_stl_format<R: Read + Seek>(reader: &mut R) -> Result<StlFormat>

Detects whether an STL file is binary or ASCII.

Uses the reliable size-formula check to disambiguate binary files whose headers begin with the ASCII text “solid” (a common case with many CAD tools).

Arguments

• reader - Any type implementing Read + Seek

Returns

• StlFormat::Binary if the file matches the binary STL size formula, or if the first 5 bytes are not solid (case-insensitive).
• StlFormat::Ascii otherwise.

After return, the reader position is reset to 0.