bitcoin-random 0.1.21

random numbers in bitcoin
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// ---------------- [ File: bitcoin-random/src/strengthen.rs ]
crate::ix!();

/**
  | Use repeated SHA512 to strengthen the
  | randomness in seed32, and feed into
  | hasher.
  |
  */
pub fn strengthen(
        seed:         &[u8; 32],
        microseconds: i32,
        hasher:       &mut Sha512)  {

    let microseconds: i64 = microseconds.into();

    let mut inner_hasher: Sha512 = Sha512::default();

    inner_hasher.write(seed.as_ptr() as *const u8, size_of_val(seed));

    // Hash loop
    let mut buffer: [u8; 64] = unsafe { std::mem::zeroed() };

    let stop: Instant = get_time() + Duration::microseconds(microseconds);

    loop {

        for i in 0..1000 {
            inner_hasher.finalize(&mut buffer);
            inner_hasher.reset();
            inner_hasher.write(buffer.as_mut_ptr() as *const u8, size_of_val(&buffer));
        }

        // Benchmark operation and feed it into outer hasher.
        let perf: i64 = get_performance_counter();

        hasher.write(&perf as *const _ as *const u8, size_of_val(&perf));

        if get_time() >= stop {
            break;
        }
    }

    // Produce output from inner state and feed it to outer hasher.
    inner_hasher.finalize(&mut buffer);
    hasher.write(buffer.as_mut_ptr() as *const u8, size_of_val(&buffer));

    // Try to clean up.
    inner_hasher.reset();

    memory_cleanse(buffer.as_mut_ptr() as *mut c_void, size_of_val(&buffer));
}

#[cfg(test)]
mod strengthen_spec {
    use super::*;

    #[traced_test]
    fn strengthen_adds_material_to_hasher_even_for_short_durations() {
        let mut h = Sha512::default();
        let before = h.size();
        let seed = [0u8; 32];
        strengthen(&seed, 1, &mut h);
        assert!(h.size() > before);
    }
}