Add comments for base32 file

Author: jbesraa

lightning/src/util/base32.rs

@@ -20,18 +20,22 @@
 // SOFTWARE.
 // (reference https://github.com/andreasots/base32/blob/master/LICENSE-MIT)
 
+/// Alphabet used for encoding and decoding.
 #[derive(Copy, Clone)]
 pub enum Alphabet {
-    // RFC4648
+    /// RFC4648 base32 encoding. padding: bool indicates whether to use padding.
     RFC4648 { padding: bool },
-    // Crockford
+    /// Crockford base32 encoding.
     Crockford,
 }
 
+/// RFC4648 base32 encoding with padding.
 const RFC4648_ALPHABET: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+
+/// Crockford base32 encoding.
 const CROCKFORD_ALPHABET: &'static [u8] = b"0123456789ABCDEFGHJKMNPQRSTVWXYZ";
 
-// Encode a byte slice into a base32 string.
+/// Encode a byte slice into a base32 string.
 pub fn encode(alphabet: Alphabet, data: &[u8]) -> String {
     let (alphabet, padding) = match alphabet {
         Alphabet::RFC4648 { padding } => (RFC4648_ALPHABET, padding),
@@ -72,10 +76,13 @@ pub fn encode(alphabet: Alphabet, data: &[u8]) -> String {
     String::from_utf8(ret).unwrap()
 }
 
+/// Inverse RFC4648 lookup table for decoding.
 const RFC4648_INV_ALPHABET: [i8; 43] = [
     -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, 0, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
     9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
 ];
+
+/// Inverse Crockford lookup table for decoding.
 const CROCKFORD_INV_ALPHABET: [i8; 43] = [
     0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 1,
     18, 19, 1, 20, 21, 0, 22, 23, 24, 25, 26, -1, 27, 28, 29, 30, 31,