Function ravg_read

pub fn ravg_read(
    val: u64,
    val_at: u64,
    old: u64,
    cur: u64,
    now: u64,
    half_life: u32,
    frac_bits: u32,
) -> f64

Read the current running average

Read the running average value at @now of ravg_data (@val, @val_at, @old, @cur) given @half_life and @frac_bits. This is equivalent to C ravg_read().

There currently is no way to make bindgen and libbpf_cargo generated code to use a pre-existing type, so this function takes each field of struct ravg_data as a separate argument. This works but is ugly and error-prone. Something to improve in the future.