sharding

src/sharding.rs

@@ -0,0 +1,33 @@
+use sha1::{Digest, Sha1};
+
+pub struct Sharder {
+    shards: usize,
+}
+
+impl Sharder {
+    pub fn new(shards: usize) -> Sharder {
+        Sharder { shards: shards }
+    }
+
+    pub fn sha1(&self, key: &[u8]) -> usize {
+        let mut hasher = Sha1::new();
+        hasher.update(key);
+        let result = hasher.finalize_reset();
+
+        let i = u32::from_le_bytes(result[result.len() - 4..result.len()].try_into().unwrap());
+        i as usize % self.shards
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_sha1() {
+        let sharder = Sharder::new(12);
+        let key = b"1234";
+        let shard = sharder.sha1(key);
+        assert_eq!(shard, 1);
+    }
+}