Module io 

Functions

create_dir_all

file_exists

has_matching_version

Look for a # version: N line near the top of a cache file and return true if it parses to exactly expected. Older caches without the line, caches with a newer/older N, and malformed lines all return false so the caller can silently regenerate. Stops scanning at the first non-comment line to keep the cost bounded.

is_dir

list_directory

Plain readdir returning names (excluding . and ..). Order undefined.

read_file

write_file_if_changed

Returns true if the file was written, false if it was already byte-identical.