Function generate_ulid_lowercased

atomic-cli/src/commands/memory/new.rs:203–222

Generate a fresh lowercased ULID-style stem: a 48-bit millisecond timestamp followed by 80 bits of randomness, encoded in Crockford base32 (26 chars), lowercased. No ULID crate is a workspace dependency, so this is a self-contained generator using the existing `chrono` + `uuid` deps — deliberately NOT a `PREFIX-N` scheme (memories have no prefix allocator).

()

/// self-contained generator using the existing `chrono` + `uuid` deps —
/// deliberately NOT a `PREFIX-N` scheme (memories have no prefix allocator).
fn generate_ulid_lowercased() -> String {
    const CROCKFORD: &[u8; 32] = b"0123456789abcdefghjkmnpqrstvwxyz";

    let now_ms = chrono::Utc::now().timestamp_millis().max(0) as u128;
    // 80 bits of randomness from a v4 UUID.
    let rand = uuid::Uuid::new_v4().as_u128();

    // A ULID is a 128-bit value: 48-bit time (high) + 80-bit randomness (low).
    let value: u128 = (now_ms << 80) | (rand & ((1u128 << 80) - 1));

    // Encode the 128-bit value as 26 Crockford base32 chars (130 bits, so the
    // top 2 bits of the first symbol are always 0 — standard ULID layout).
    let mut out = [0u8; 26];
    let mut v = value;
    for slot in out.iter_mut().rev() {
        *slot = CROCKFORD[(v & 0x1f) as usize];
        v >>= 5;
    }
    String::from_utf8(out.to_vec()).expect("crockford alphabet is valid ASCII")
}

#[cfg(test)]
mod tests {