implement Hasher trait for Hasher

src/lib.rs

@@ -99,6 +99,7 @@ use arrayref::{array_mut_ref, array_ref};
 use arrayvec::{ArrayString, ArrayVec};
 use core::cmp;
 use core::fmt;
+use core::hash;
 use join::{Join, SerialJoin};
 use platform::{Platform, MAX_SIMD_DEGREE, MAX_SIMD_DEGREE_OR_2};
 
@@ -1201,6 +1202,21 @@ impl Hasher {
     }
 }
 
+impl hash::Hasher for Hasher {
+    fn finish(&self) -> u64 {
+        let mut bytes = [0; 8];
+
+        self.finalize_xof().fill(&mut bytes);
+
+        u64::from_be_bytes(bytes)
+    }
+
+    #[inline]
+    fn write(&mut self, bytes: &[u8]) {
+        self.update(bytes);
+    }
+}
+
 // Don't derive(Debug), because the state may be secret.
 impl fmt::Debug for Hasher {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

src/test.rs

@@ -551,3 +551,44 @@ fn test_join_lengths() {
     );
     assert_eq!(CUSTOM_JOIN_CALLS.load(Ordering::SeqCst), 1);
 }
+
+#[test]
+fn test_hasher_hasher() {
+    use crate::Hasher;
+
+    let buffer = [
+        100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117,
+        118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135,
+        136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153,
+        154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171,
+        172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189,
+        190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207,
+        208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225,
+        226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243,
+        244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255,
+    ];
+    let mut hasher = Hasher::new();
+
+    <Hasher as core::hash::Hasher>::write(&mut hasher, &buffer[..78]);
+
+    assert_eq!(<Hasher as core::hash::Hasher>::finish(&hasher), {
+        let mut bytes = [0; 8];
+        Hasher::new()
+            .update(&buffer[..78])
+            .finalize_xof()
+            .fill(&mut bytes);
+        u64::from_be_bytes(bytes)
+    });
+
+    <Hasher as core::hash::Hasher>::write(&mut hasher, &buffer[78..]);
+
+    assert_eq!(<Hasher as core::hash::Hasher>::finish(&hasher), {
+        let mut bytes = [0; 8];
+        Hasher::new()
+            .update(&buffer[..78])
+            .update(&buffer[78..])
+            .finalize_xof()
+            .fill(&mut bytes);
+        u64::from_be_bytes(bytes)
+    });
+}