hash to get tags, make tagging a feature

Cargo.toml

@@ -13,12 +13,14 @@ keywords = ["sql", "id", "encode", "obfuscate"]
 categories = ["cryptography", "encoding", "no-std"]
 
 [features]
-default = ["std"]
+default = ["std", "tag"]
 std = []
+tag = ["dep:const-fnv1a-hash"]
 zeroize = ["aes/zeroize"]
 
 [dependencies]
 aes = "0.8.4"
+const-fnv1a-hash = { version = "1.1.0", optional = true }
 
 [dev-dependencies]
 prop-test = "0.1.1"
@@ -28,3 +30,6 @@ opt-level = 3
 
 [profile.test.package.rand_chacha]
 opt-level = 3
+
+[package.metadata."docs.rs"]
+all-features = true

README.md

@@ -55,8 +55,8 @@ let cipher = Aes128::new(&key.into());
 let user_id = UserId::new(1, &cipher);
 let crate_id = CrateId::new(1, &cipher);
 
-assert_eq!("mC67zUocKZHWRXCHBr4aj52", &user_id.to_string());
-assert_eq!("oPnmjU48WRy4GNradtqYdX2", &crate_id.to_string());
+assert_eq!("qXfXkNN9ReZCGXu3qi28xC2", &user_id.to_string());
+assert_eq!("VgtE1tzjDEHnjd3fh3PwiT2", &crate_id.to_string());
 ```
 
 # Comparison

src/id.rs

@@ -14,18 +14,6 @@ use crate::{
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub struct Id<const TAG: u64>(u128);
 
-pub const fn tag(tag: &str) -> u64 {
-    assert!(tag.len() <= 8, "tag is too long");
-    let mut byte_block = [0; 8];
-    let tag = tag.as_bytes();
-    let mut i = 0;
-    while i < tag.len() {
-        byte_block[i] = tag[i];
-        i += 1;
-    }
-    u64::from_be_bytes(byte_block)
-}
-
 impl<const TAG: u64> Id<TAG> {
     pub fn new(id: i64, cipher: &Aes128) -> Self {
         Self(encrypt(TAG, id, cipher))

src/lib.rs

@@ -10,11 +10,15 @@ mod encryption;
 mod error;
 mod id;
 
+#[cfg(feature = "tag")]
+mod tag;
+
 pub use aes;
 
-pub use self::{
-    error::Error,
-    id::{tag, Id},
-};
+pub use error::Error;
+pub use id::Id;
+
+#[cfg(feature = "tag")]
+pub use tag::tag;
 
 pub type Result<T> = core::result::Result<T, Error>;

src/tag.rs

@@ -0,0 +1,3 @@
+pub const fn tag(tag: &str) -> u64 {
+    const_fnv1a_hash::fnv1a_hash_str_64(tag)
+}