From 368f4ef468ca97fd4757c896f53349d9fa4def1b Mon Sep 17 00:00:00 2001
From: Urgau <urgau@numericable.fr>
Date: Sun, 14 Jul 2024 23:37:13 +0200
Subject: [PATCH] WIP: Blake3 stable hasher

---
 Cargo.lock    | 46 ++++++++++++++++++++++++++++++++++++++++
 Cargo.toml    |  3 +++
 src/blake3.rs | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs    |  9 ++++++++
 4 files changed, 116 insertions(+)
 create mode 100644 src/blake3.rs

diff --git a/Cargo.lock b/Cargo.lock
index d0752af..e3de2db 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,52 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "arrayref"
+version = "0.3.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6b4930d2cb77ce62f89ee5d5289b4ac049559b1c45539271f5ed4fdc7db34545"
+
+[[package]]
+name = "arrayvec"
+version = "0.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96d30a06541fbafbc7f82ed10c06164cfbd2c401138f6addd8404629c4b16711"
+
+[[package]]
+name = "blake3"
+version = "1.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3d08263faac5cde2a4d52b513dadb80846023aade56fcd8fc99ba73ba8050e92"
+dependencies = [
+ "arrayref",
+ "arrayvec",
+ "cc",
+ "cfg-if",
+ "constant_time_eq",
+]
+
+[[package]]
+name = "cc"
+version = "1.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9711f33475c22aab363b05564a17d7b789bf3dfec5ebabb586adee56f0e271b5"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "constant_time_eq"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7144d30dcf0fafbce74250a3963025d8d52177934239851c917d29f1df280c2"
+
 [[package]]
 name = "rustc-stable-hash"
 version = "0.1.0"
+dependencies = [
+ "blake3",
+]
diff --git a/Cargo.toml b/Cargo.toml
index 976ab8c..c4d14f7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,5 +7,8 @@ readme = "README.md"
 repository = "https://github.com/rust-lang/rustc-stable-hash"
 edition = "2021"
 
+[dependencies]
+blake3 = { version = "1.5", default-features = false, optional = true }
+
 [features]
 nightly = [] # for feature(hasher_prefixfree_extras)
diff --git a/src/blake3.rs b/src/blake3.rs
new file mode 100644
index 0000000..fc1eb48
--- /dev/null
+++ b/src/blake3.rs
@@ -0,0 +1,58 @@
+//! This is the adapted version of the official Blake 3 implementation providing 256 bit hashes.
+
+use std::hash::Hasher;
+
+use crate::ExtendedHasher;
+
+/// Hash type for the [`Blake3Hash`], providing 256 bit hashses.
+pub type Blake3Hash = blake3::Hash;
+
+/// Blake 3 implementation
+#[derive(Debug, Clone)]
+pub struct Blake3Hasher {
+    state: blake3::Hasher,
+}
+
+impl Default for Blake3Hasher {
+    fn default() -> Blake3Hasher {
+        Blake3Hasher {
+            state: Default::default(),
+        }
+    }
+}
+
+impl ExtendedHasher for Blake3Hasher {
+    type Hash = Blake3Hash;
+
+    #[inline]
+    fn finish(self) -> Self::Hash {
+        self.state.finalize()
+    }
+}
+
+impl Hasher for Blake3Hasher {
+    #[inline]
+    fn write(&mut self, bytes: &[u8]) {
+        self.state.update(bytes);
+    }
+
+    #[inline]
+    fn finish(&self) -> u64 {
+        let hash = self.state.finalize();
+
+        // todo: godbolt
+        let [a0, a1, a2, a3, a4, a5, a6, a7, b0, b1, b2, b3, b4, b5, b6, b7, c0, c1, c2, c3, c4, c5, c6, c7, d0, d1, d2, d3, d4, d5, d6, d7] =
+            *hash.as_bytes();
+
+        let p0 = u64::from_ne_bytes([a0, a1, a2, a3, a4, a5, a6, a7]);
+        let p1 = u64::from_ne_bytes([b0, b1, b2, b3, b4, b5, b6, b7]);
+        let p2 = u64::from_ne_bytes([c0, c1, c2, c3, c4, c5, c6, c7]);
+        let p3 = u64::from_ne_bytes([d0, d1, d2, d3, d4, d5, d6, d7]);
+
+        p0.wrapping_mul(3)
+            .wrapping_add(p1)
+            .wrapping_add(p2)
+            .wrapping_mul(p3)
+            .to_le()
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index e68d2d1..95d6ac3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,8 @@
 #![deny(unsafe_op_in_unsafe_fn)]
 #![deny(unreachable_pub)]
 
+#[cfg(feature = "blake3")]
+mod blake3;
 mod int_overflow;
 mod sip128;
 mod stable_hasher;
@@ -14,12 +16,19 @@ pub mod hashers {
     #[doc(inline)]
     pub use super::sip128::{SipHasher128, SipHasher128Hash};
 
+    #[cfg(feature = "blake3")]
+    #[doc(inline)]
+    pub use super::blake3::{Blake3Hash, Blake3Hasher};
+
     /// Stable 128-bits Sip Hasher
     ///
     /// [`StableHasher`] version of [`SipHasher128`].
     ///
     /// [`StableHasher`]: super::StableHasher
     pub type StableSipHasher128 = super::StableHasher<SipHasher128>;
+
+    #[cfg(feature = "blake3")]
+    pub type StableBlake3Hasher = super::StableHasher<Blake3Hasher>;
 }
 
 #[doc(inline)]