Variable block size.

src/block.rs

@@ -0,0 +1,31 @@
+use std::mem;
+
+pub trait BitBlock {
+    const ONE: Self;
+    const ZERO: Self;
+
+    fn bits() -> usize;
+    fn count_ones(self) -> usize;
+}
+
+macro_rules! bit_block_impl {
+    ($(($t: ty, $size: expr)),*) => ($(
+        impl BitBlock for $t {
+            const ONE: Self = 1;
+            const ZERO: Self = 1;
+
+            #[inline]
+            fn bits() -> usize { $size }
+            #[inline]
+            fn count_ones(self) -> usize { self.count_ones() as usize }
+        }
+    )*)
+}
+
+bit_block_impl!{
+    (u8, 8),
+    (u16, 16),
+    (u32, 32),
+    (u64, 64),
+    (usize, mem::size_of::<usize>() * 8)
+}

src/lib.rs

@@ -12,6 +12,7 @@ use serde::ser::SerializeSeq;
 use serde::de::{SeqAccess, Visitor};
 
 mod hasher;
+mod block;
 
 use hasher::BitBuildHasher;