From 035b663023e49606c2d26411a22b222fb64e27eb Mon Sep 17 00:00:00 2001
From: parazyd <parazyd@dyne.org>
Date: Mon, 28 Aug 2023 12:53:51 +0200
Subject: [PATCH] Add common hash sizes From impls

blake2s:
    * From<[u8; 16]>

blake2b:
    * From<[u8; 16]>
    * From<[u8; 32]>

Both introduce an intermediate buffer in the implementation, but
this is a small tradeoff that allows usage of some common hash
sizes more idiomatically for the users of this library.
---
 blake2b/src/lib.rs  | 34 ++++++++++++++++++++++++++++++++++
 blake2b/src/test.rs | 20 ++++++++++++++++++++
 blake2s/src/lib.rs  | 17 +++++++++++++++++
 blake2s/src/test.rs | 10 ++++++++++
 4 files changed, 81 insertions(+)

diff --git a/blake2b/src/lib.rs b/blake2b/src/lib.rs
index 6c4f92f..38ac13d 100644
--- a/blake2b/src/lib.rs
+++ b/blake2b/src/lib.rs
@@ -616,6 +616,40 @@ fn bytes_to_hex(bytes: &[u8]) -> HexString {
     s
 }
 
+impl From<[u8; 16]> for Hash {
+    fn from(bytes: [u8; 16]) -> Self {
+        let mut buf = [0u8; OUTBYTES];
+        buf[0..16].copy_from_slice(&bytes);
+        Self {
+            bytes: buf,
+            len: 16 as u8,
+        }
+    }
+}
+
+impl From<&[u8; 16]> for Hash {
+    fn from(bytes: &[u8; 16]) -> Self {
+        Self::from(*bytes)
+    }
+}
+
+impl From<[u8; 32]> for Hash {
+    fn from(bytes: [u8; 32]) -> Self {
+        let mut buf = [0u8; OUTBYTES];
+        buf[0..32].copy_from_slice(&bytes);
+        Self {
+            bytes: buf,
+            len: 32 as u8,
+        }
+    }
+}
+
+impl From<&[u8; 32]> for Hash {
+    fn from(bytes: &[u8; 32]) -> Self {
+        Self::from(*bytes)
+    }
+}
+
 impl From<[u8; OUTBYTES]> for Hash {
     fn from(bytes: [u8; OUTBYTES]) -> Self {
         Self {
diff --git a/blake2b/src/test.rs b/blake2b/src/test.rs
index 0c7e5c7..00d9a7d 100644
--- a/blake2b/src/test.rs
+++ b/blake2b/src/test.rs
@@ -205,4 +205,24 @@ fn test_hash_from() {
     let h = blake2b(b"foo");
     assert_eq!(h, Hash::from(h.as_array()));
     assert_eq!(h, Hash::from(*h.as_array()));
+
+    let h = crate::Params::new()
+        .hash_length(16)
+        .to_state()
+        .update(b"foo")
+        .finalize();
+    let mut h_s = [0u8; 16];
+    h_s[0..16].copy_from_slice(h.as_bytes());
+    assert_eq!(h, Hash::from(&h_s));
+    assert_eq!(h, Hash::from(h_s));
+
+    let h = crate::Params::new()
+        .hash_length(32)
+        .to_state()
+        .update(b"foo")
+        .finalize();
+    let mut h_s = [0u8; 32];
+    h_s[0..32].copy_from_slice(h.as_bytes());
+    assert_eq!(h, Hash::from(&h_s));
+    assert_eq!(h, Hash::from(h_s));
 }
diff --git a/blake2s/src/lib.rs b/blake2s/src/lib.rs
index f845e96..82a8929 100644
--- a/blake2s/src/lib.rs
+++ b/blake2s/src/lib.rs
@@ -608,6 +608,23 @@ fn bytes_to_hex(bytes: &[u8]) -> HexString {
     s
 }
 
+impl From<[u8; 16]> for Hash {
+    fn from(bytes: [u8; 16]) -> Self {
+        let mut buf = [0u8; OUTBYTES];
+        buf[0..16].copy_from_slice(&bytes);
+        Self {
+            bytes: buf,
+            len: 16 as u8,
+        }
+    }
+}
+
+impl From<&[u8; 16]> for Hash {
+    fn from(bytes: &[u8; 16]) -> Self {
+        Self::from(*bytes)
+    }
+}
+
 impl From<[u8; OUTBYTES]> for Hash {
     fn from(bytes: [u8; OUTBYTES]) -> Self {
         Self {
diff --git a/blake2s/src/test.rs b/blake2s/src/test.rs
index 651cb28..897eddb 100644
--- a/blake2s/src/test.rs
+++ b/blake2s/src/test.rs
@@ -212,4 +212,14 @@ fn test_hash_from() {
     let h = blake2s(b"foo");
     assert_eq!(h, Hash::from(h.as_array()));
     assert_eq!(h, Hash::from(*h.as_array()));
+
+    let h = crate::Params::new()
+        .hash_length(16)
+        .to_state()
+        .update(b"foo")
+        .finalize();
+    let mut h_s = [0u8; 16];
+    h_s[0..16].copy_from_slice(h.as_bytes());
+    assert_eq!(h, Hash::from(&h_s));
+    assert_eq!(h, Hash::from(h_s));
 }