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//! Minimal ULID generator — no external dependencies.
//!
//! Replaces the `ulid` crate (and its `rand` chain) with a small inline
//! implementation: 48-bit ms timestamp | 80-bit OS random, Crockford Base32.
const CROCKFORD: &[u8; 32] = b"0123456789ABCDEFGHJKMNPQRSTVWXYZ";
/// Generate a new ULID string (26 uppercase Crockford Base32 characters).
pub fn new_ulid() -> String {
let ts_ms = std::time::SystemTime::now()
.duration_since(std::time::UNIX_EPOCH)
.unwrap_or_default()
.as_millis() as u64;
let mut rand_bytes = [0u8; 10];
os_rand(&mut rand_bytes);
// Pack: 6 bytes timestamp (high 48 bits) | 10 bytes random (low 80 bits)
let mut raw = [0u8; 16];
let ts = ts_ms.to_be_bytes();
raw[0..6].copy_from_slice(&ts[2..8]);
raw[6..16].copy_from_slice(&rand_bytes);
encode(u128::from_be_bytes(raw))
}
/// Returns true if `s` is a syntactically valid 26-character ULID.
pub fn is_valid(s: &str) -> bool {
let b = s.as_bytes();
b.len() == 26 && b.iter().all(|c| CROCKFORD.contains(c))
}
fn os_rand(buf: &mut [u8]) {
use std::io::Read;
if let Ok(mut f) = std::fs::File::open("/dev/urandom") {
f.read_exact(buf).ok();
}
}
fn encode(mut value: u128) -> String {
let mut chars = [0u8; 26];
for ch in chars.iter_mut().rev() {
*ch = CROCKFORD[(value & 0x1F) as usize];
value >>= 5;
}
// Safety: all bytes are ASCII from CROCKFORD table
unsafe { String::from_utf8_unchecked(chars.to_vec()) }
}