Extract common code from the 17 to 128 bytes implementation

shepmaster · Nov 1, 2024 · 53cab0d · 53cab0d
1 parent 4c2d379
commit 53cab0d
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Showing 2 changed files with 32 additions and 24 deletions.
diff --git a/src/xxhash3.rs b/src/xxhash3.rs
@@ -121,6 +121,34 @@ pub fn impl_1_to_3_bytes_combined(input: &[u8]) -> u32 {
         | input[input.len() >> 1].into_u32() << 24
 }
 
+#[inline]
+pub fn impl_17_to_128_bytes_iter(
+    secret: &Secret,
+    input: &[u8],
+    mut f: impl FnMut(&[u8; 16], &[u8; 16], &[[u8; 16]; 2]),
+) {
+    let secret = secret.words_for_17_to_128();
+    let (secret, _) = secret.bp_as_chunks::<2>();
+    let (fwd, _) = input.bp_as_chunks();
+    let (_, bwd) = input.bp_as_rchunks();
+
+    let q = bwd.len();
+
+    if input.len() > 32 {
+        if input.len() > 64 {
+            if input.len() > 96 {
+                f(&fwd[3], &bwd[q - 4], &secret[3]);
+            }
+
+            f(&fwd[2], &bwd[q - 3], &secret[2]);
+        }
+
+        f(&fwd[1], &bwd[q - 2], &secret[1]);
+    }
+
+    f(&fwd[0], &bwd[q - 1], &secret[0]);
+}
+
 #[inline]
 pub fn mix_step(data: &[u8; 16], secret: &[u8; 16], seed: u64) -> u64 {
     let data_words = to_u64s(data);

diff --git a/src/xxhash3_64.rs b/src/xxhash3_64.rs
@@ -296,30 +296,10 @@ fn impl_17_to_128_bytes(secret: &Secret, seed: u64, input: &[u8]) -> u64 {
     assert_input_range!(17..=128, input.len());
     let mut acc = input.len().into_u64().wrapping_mul(PRIME64_1);
 
-    let secret = secret.words_for_17_to_128();
-    let (secret, _) = secret.bp_as_chunks::<2>();
-    let (fwd, _) = input.bp_as_chunks();
-    let (_, bwd) = input.bp_as_rchunks();
-
-    let q = bwd.len();
-
-    if input.len() > 32 {
-        if input.len() > 64 {
-            if input.len() > 96 {
-                acc = acc.wrapping_add(mix_step(&fwd[3], &secret[3][0], seed));
-                acc = acc.wrapping_add(mix_step(&bwd[q - 4], &secret[3][1], seed));
-            }
-
-            acc = acc.wrapping_add(mix_step(&fwd[2], &secret[2][0], seed));
-            acc = acc.wrapping_add(mix_step(&bwd[q - 3], &secret[2][1], seed));
-        }
-
-        acc = acc.wrapping_add(mix_step(&fwd[1], &secret[1][0], seed));
-        acc = acc.wrapping_add(mix_step(&bwd[q - 2], &secret[1][1], seed));
-    }
-
-    acc = acc.wrapping_add(mix_step(&fwd[0], &secret[0][0], seed));
-    acc = acc.wrapping_add(mix_step(&bwd[q - 1], &secret[0][1], seed));
+    impl_17_to_128_bytes_iter(secret, input, |fwd, bwd, secret| {
+        acc = acc.wrapping_add(mix_step(fwd, &secret[0], seed));
+        acc = acc.wrapping_add(mix_step(bwd, &secret[1], seed));
+    });
 
     avalanche(acc)
 }