use crate::minrandom;
#[macro_export]
macro_rules! gen {
($mod:tt, $len:tt, $alphabet:tt) => {
#[doc = concat!(" Nanoid with alphabet table `", stringify!($alphabet), "`")]
mod $mod {
pub const MASK: usize = ($len as usize).next_power_of_two() - 1;
pub const ALPHABET: &'static [u8; $len] = $alphabet;
}
#[doc = concat!(" Nanoid with ", stringify!($mod))]
#[must_use]
pub fn $mod<const N: usize>() -> String {
let mut bytes = vec![0u8; 8 * N / 5];
let mut id = String::with_capacity(N);
loop {
minrandom::fill_buf(&mut bytes);
for byte in &bytes {
let idx = *byte as usize & $mod::MASK;
if idx < $len {
id.push($mod::ALPHABET[idx] as char)
}
if id.len() == N {
return id;
}
}
}
}
};
}
gen!(
base62,
62,
b"ModuleSymbhasOwnPr0123456789ABCDEFGHNRVfgctiUvzKqYTJkLxpZXIjQW"
);
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn generates_base62() {
let id = base62::<21>();
println!("{}", &id);
assert_eq!(id.len(), 21);
}
#[test]
fn generates_uid() {
gen!(
uid,
64,
b"_-0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
);
let id = uid::<21>();
println!("{}", &id);
assert_eq!(id.len(), 21);
}
#[test]
fn symbols() {
use std::collections::BTreeMap;
let mut counts = BTreeMap::new();
for _ in 0..1_000_000 {
let id = base62::<10>();
for c in id.chars() {
*counts.entry(c).or_insert(0) += 1;
}
}
println!("{} symbols generated", counts.len());
for (c, count) in &counts {
println!("{}: {}", c, count);
}
assert_eq!(counts.len(), 62);
}
}