Function entity_count 

pub fn entity_count<T>(content: &T) -> usize
where
    T: AsRef<[u8]> + ?Sized,

Count the entities in a STEP/IFC byte buffer in O(scan) time and O(1) memory — no entity index, no per-type map.

A thin wrapper over EntityScanner::count. This is the cheap primitive a downstream can use to reject a file with a pathologically large entity count that a byte-size cap would miss, WITHOUT paying the ~20 B/entity the full index costs (issue #1517). Header-aware and comment-/string-safe, exactly like the scanner (it IS the scanner), so the count matches what build_entity_index would find.