use std::str;
pub const MAX_BASE: u64 = 64;
pub const ALPHANUMERIC_ONLY: u64 = 62;
const BASE_64: &'static [u8; MAX_BASE as usize] =
b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ@$";
#[inline]
pub fn push_str(mut n: u64, base: u64, output: &mut String) {
debug_assert!(base >= 2 && base <= MAX_BASE);
let mut s = [0u8; 64];
let mut index = 0;
loop {
s[index] = BASE_64[(n % base) as usize];
index += 1;
n /= base;
if n == 0 {
break;
}
}
&mut s[0..index].reverse();
output.push_str(str::from_utf8(&s[0..index]).unwrap());
}
#[inline]
pub fn encode(n: u64, base: u64) -> String {
let mut s = String::with_capacity(13);
push_str(n, base, &mut s);
s
}
#[test]
fn test_encode() {
fn test(n: u64, base: u64) {
assert_eq!(Ok(n), u64::from_str_radix(&encode(n, base), base as u32));
}
for base in 2..37 {
test(0, base);
test(1, base);
test(35, base);
test(36, base);
test(37, base);
test(u64::max_value(), base);
for i in 0 .. 1_000 {
test(i * 983, base);
}
}
}