Displays LtHash's Checksum as base58 (anza-xyz#3142)

lattice-hash/Cargo.toml

@@ -10,6 +10,7 @@ edition = { workspace = true }
 [dependencies]
 base64 = { workspace = true }
 blake3 = { workspace = true }
+bs58 = { workspace = true }
 bytemuck = { workspace = true, features = ["must_cast"] }
 
 [dev-dependencies]

lattice-hash/src/lt_hash.rs

@@ -1,6 +1,6 @@
 use {
     base64::{display::Base64Display, prelude::BASE64_STANDARD},
-    std::fmt,
+    std::{fmt, str},
 };
 
 /// A 16-bit, 1024 element lattice-based incremental hash based on blake3
@@ -77,8 +77,14 @@ impl Checksum {
 
 impl fmt::Display for Checksum {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let base64 = Base64Display::new(&self.0, &BASE64_STANDARD);
-        write!(f, "{base64}")
+        /// Maximum string length of a base58 encoded Checksum.
+        const MAX_BASE58_LEN: usize = 44;
+        let mut buf = [0u8; MAX_BASE58_LEN];
+        // SAFETY: The only error is if the buffer is too small
+        let len = bs58::encode(&self.0).onto(buf.as_mut_slice()).unwrap();
+        // SAFETY: The base58 alphabet is utf8
+        let str = str::from_utf8(&buf[..len]).unwrap();
+        write!(f, "{str}")
     }
 }
 
@@ -377,4 +383,12 @@ mod tests {
             assert_eq!(actual_checksum, expected_checksum);
         }
     }
+
+    #[test]
+    fn test_checksum_display() {
+        let lt_hash = LtHash::identity();
+        let checksum = lt_hash.checksum();
+        let str = checksum.to_string();
+        assert_eq!(str.as_str(), "DoL6fvKuTpTQCyUh83NxQw2ewKzWYtq9gsTKp1eQiGC2");
+    }
 }