Function extract_file 

pub async fn extract_file(path: &Path, filename: &str) -> String

Reads (the beginning of) a stored file and extracts its text. A large plain-text file (solver log, print output) keeps its end as well: the text of the beginning, the marker TAIL_MARK and the text of the last TAIL_READ (64 KiB) bytes – where a solver writes its status and final values. The end is only added when the beginning was text and the end is text in the same encoding (no NUL, no UTF-16 byte order mark at the start).