Function pio_read_dir 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn pio_read_dir(
    dir: *const c_char,
    from: *const c_char,
    scenario: i64,
    errbuf: *mut c_char,
    errlen: usize,
) -> *mut PioNetwork

Read one scenario of a dataset directory in the named from format into a network handle: the directory sibling of pio_parse_file. gridfm (the gridfm-datakit Parquet layout; dir resolves leniently: the raw/ leaf, a <case>/ directory with a raw/ child, or a parent holding exactly one such case) is the one dataset format today. scenario selects within a multi-scenario dataset (pio_scenario_ids enumerates them); formats without scenarios take 0. Read fidelity warnings attach to the handle (pio_warnings). Returns NULL on error and writes the message into errbuf. Free the handle with pio_network_free. Built --features gridfm.