1 files changed, 54 insertions, 0 deletions
diff --git a/src/base62.rs b/src/base62.rs
new file mode 100644
index 0000000..6ec1e62
--- /dev/null
+++ b/src/base62.rs
@@ -0,0 +1,54 @@
+use std::iter;
+use itertools;
+
+pub const BASE: u8 = 62;
+pub const ALPHABET: &'static [u8; BASE as usize] = 
+    b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+pub fn number_to_digits(mut x: u128, base: u8) -> Vec<u8> {
+    let mut out = Vec::new();
+    let base = base as u128;
+    while x > base {
+        out.push((x % base) as u8);
+        x /= base;
+    }
+    out.push(x as u8);
+    out.reverse();
+    out
+}
+
+pub fn digits_to_number<I>(x: I, base: u8) -> u128
+where I: Iterator<Item=u8> {
+    let base = base as u128;
+    x.fold(0, |out, digit| out * base + digit as u128)
+}
+
+pub fn digits_to_string<'a, I>(x: I, alphabet: &'a [u8]) -> String
+where I: Iterator<Item=u8> {
+    x.map(|d| alphabet[d as usize] as char).collect()
+
+}
+
+#[cfg(test)]
+mod test {
+    use crate::base62::*;
+
+    #[test]
+    fn test_number_to_digits() {
+        assert_eq!(vec![0], number_to_digits(0, 10));
+        assert_eq!(vec![8], number_to_digits(8, BASE));
+        assert_eq!(vec![1, 2], number_to_digits(64, BASE));
+        assert_eq!(vec![6, 4], number_to_digits(64, 10));
+    }
+
+    #[test]
+    fn test_digits_to_number() {
+        assert_eq!(digits_to_number(vec![1u8, 2].into_iter(), BASE), 64);
+        assert_eq!(digits_to_number(vec![6u8, 4].into_iter(), 10), 64);
+    }
+
+    #[test]
+    fn test_digits_to_string() {
+        assert_eq!(digits_to_string(vec![1u8, 2].into_iter(), ALPHABET), "12");
+    }
+}