From e2f9bdd52ec5842dc3b745e2b483fd3d0bcc9e86 Mon Sep 17 00:00:00 2001
From: Russell Banks <74878137+russellbanks@users.noreply.github.com>
Date: Tue, 12 Dec 2023 13:50:45 +0000
Subject: [PATCH] Use fast32 to encode hash with Crockford Base32

---
 Cargo.toml |  3 ++-
 README.md  |  6 +++---
 src/lib.rs | 33 +++++++++++----------------------
 3 files changed, 16 insertions(+), 26 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 7be2763..e790886 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "package-family-name"
-version = "1.0.0"
+version = "1.1.0"
 edition = "2021"
 license = "MIT OR Apache-2.0"
 categories = ["no-std"]
@@ -10,4 +10,5 @@ readme = "README.md"
 repository = "https://github.com/russellbanks/package-family-name"
 
 [dependencies]
+fast32 = "1"
 sha2 = { version = "0.10", default-features = false }
diff --git a/README.md b/README.md
index 4bd7987..6d54a4f 100644
--- a/README.md
+++ b/README.md
@@ -38,9 +38,9 @@ In short, a package family name is made up of two parts:
 
 These steps are then taken:
 
-1. Calculate the SHA256 hash of the identity publisher
-2. Take the first 8 bytes of the hash
-3. Left shift all bits
+1. UTF-16 encode the identity publisher
+2. Calculate a SHA256 hash of the encoded publisher
+3. Take the first 8 bytes of the hash
 4. Encode the result with [Douglas Crockford Base32](http://www.crockford.com/base32.html)
 5. Join the identity name and the encoded value with an underscore (`AppName_zj75k085cmj1a`)
 
diff --git a/src/lib.rs b/src/lib.rs
index 54553ee..728915a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,40 +4,29 @@ extern crate alloc;
 
 use alloc::format;
 use alloc::string::String;
-use alloc::vec::Vec;
-use core::fmt::Write;
-use core::ops::Add;
+use fast32::base32::Alphabet32Nopad;
+use fast32::decoder_map_simple;
 use sha2::{Digest, Sha256};
 
 const CROCKFORD_CHARACTER_TABLE: &[u8; 32] = b"0123456789abcdefghjkmnpqrstvwxyz";
+const ENC_CROCKFORD_LOWER: [u8; 256] = decoder_map_simple(CROCKFORD_CHARACTER_TABLE);
+const CROCKFORD_LOWER: Alphabet32Nopad =
+    Alphabet32Nopad::new(CROCKFORD_CHARACTER_TABLE, &ENC_CROCKFORD_LOWER);
 
 pub fn get_package_family_name(identity_name: &str, identity_publisher: &str) -> String {
-    let result: String = identity_publisher
+    let publisher_sha_256 = identity_publisher
         .encode_utf16()
         .flat_map(u16::to_le_bytes)
         .fold(Sha256::new(), |mut buf, byte| {
             buf.update([byte]);
             buf
         })
-        .finalize()
-        .into_iter()
-        .take(8)
-        .fold(String::with_capacity(65), |mut buf, byte| {
-            let _ = write!(buf, "{:08b}", byte);
-            buf
-        })
-        .add("0")
-        .chars()
-        .collect::<Vec<_>>()
-        .chunks_exact(5)
-        .map(|chunk| {
-            let chunk_str = String::from_iter(chunk);
-            let index = usize::from_str_radix(&chunk_str, 2).unwrap_or_default();
-            CROCKFORD_CHARACTER_TABLE[index] as char
-        })
-        .collect();
+        .finalize();
 
-    format!("{identity_name}_{}", result)
+    format!(
+        "{identity_name}_{}",
+        CROCKFORD_LOWER.encode(&publisher_sha_256[..8])
+    )
 }
 
 #[cfg(test)]