From 27c05cfd533381aeb435d2c14eac94515ce4f82e Mon Sep 17 00:00:00 2001
From: Lev Kokotov <lev.kokotov@gmail.com>
Date: Tue, 8 Feb 2022 10:05:10 -0800
Subject: [PATCH] fix some bugs in sharding - still doesnt work

---
 src/sharding.rs | 52 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 20 deletions(-)

diff --git a/src/sharding.rs b/src/sharding.rs
index 39c955f..e9cd365 100644
--- a/src/sharding.rs
+++ b/src/sharding.rs
@@ -29,9 +29,7 @@ impl Sharder {
     pub fn pg_bigint_hash(&self, key: i64) -> usize {
         let mut lohalf = key as u32;
         let hihalf = (key >> 32) as u32;
-        println!("{}, {}", lohalf, hihalf);
         lohalf ^= if key >= 0 { hihalf } else { !hihalf };
-        println!("Low half: {}", lohalf);
         Self::pg_u32_hash(lohalf) as usize % self.shards
     }
 
@@ -44,45 +42,51 @@ impl Sharder {
         a = a.wrapping_sub(c);
         a ^= Self::rot(c, 4);
         c = c.wrapping_add(b);
-        b = b.wrapping_add(a);
+
+        b = b.wrapping_sub(a);
         b ^= Self::rot(a, 6);
         a = a.wrapping_add(c);
-        c = c.wrapping_add(b);
+
+        c = c.wrapping_sub(b);
         c ^= Self::rot(b, 8);
         b = b.wrapping_add(a);
-        a = a.wrapping_add(c);
+
+        a = a.wrapping_sub(c);
         a ^= Self::rot(c, 16);
         c = c.wrapping_add(b);
-        b = b.wrapping_add(a);
+
+        b = b.wrapping_sub(a);
         b ^= Self::rot(a, 19);
         a = a.wrapping_add(c);
-        c = c.wrapping_add(b);
+
+        c = c.wrapping_sub(b);
         c ^= Self::rot(b, 4);
         b = b.wrapping_add(a);
+
         (a, b, c)
     }
 
     #[inline]
     fn _final(mut a: u32, mut b: u32, mut c: u32) -> (u32, u32, u32) {
         c ^= b;
-        c = c.wrapping_add(Self::rot(b, 14));
+        c = c.wrapping_sub(Self::rot(b, 14));
         a ^= c;
-        a = a.wrapping_add(Self::rot(c, 11));
+        a = a.wrapping_sub(Self::rot(c, 11));
         b ^= a;
-        b = b.wrapping_add(Self::rot(a, 25));
+        b = b.wrapping_sub(Self::rot(a, 25));
         c ^= b;
-        c = c.wrapping_add(Self::rot(b, 16));
+        c = c.wrapping_sub(Self::rot(b, 16));
         a ^= c;
-        a = a.wrapping_add(Self::rot(c, 4));
+        a = a.wrapping_sub(Self::rot(c, 4));
         b ^= a;
-        b = b.wrapping_add(Self::rot(a, 14));
+        b = b.wrapping_sub(Self::rot(a, 14));
         c ^= b;
-        c = c.wrapping_add(Self::rot(b, 24));
+        c = c.wrapping_sub(Self::rot(b, 24));
         (a, b, c)
     }
 
-    fn pg_u32_hash(val: u32) -> u64 {
-        let mut a: u32 = 0x9e3779b9 + 4 + 3923095;
+    fn pg_u32_hash(k: u32) -> u64 {
+        let mut a: u32 = 0x9e3779b9 as u32 + std::mem::size_of::<u32>() as u32 + 3923095 as u32;
         let mut b = a;
         let c = a;
         let seed = PARTITION_HASH_SEED;
@@ -91,11 +95,11 @@ impl Sharder {
         b = b.wrapping_add(seed as u32);
         let (mut a, b, c) = Self::mix(a, b, c);
 
-        a = a.wrapping_add(val);
+        a = a.wrapping_add(k);
 
         let (a, b, c) = Self::_final(a, b, c);
 
-        (b as u64) << 32 | c as u64
+        ((b as u64) << 32) | (c as u64)
     }
 }
 
@@ -113,9 +117,17 @@ mod test {
 
     #[test]
     fn test_pg_bigint_hash() {
-        let sharder = Sharder::new(4);
-        let key = 23423423 as i64;
+        let sharder = Sharder::new(2);
+        let key = 1 as i64;
         let shard = sharder.pg_bigint_hash(key);
         assert_eq!(shard, 0);
+
+        let key = 2 as i64;
+        let shard = sharder.pg_bigint_hash(key);
+        assert_eq!(shard, 0);
+
+        let key = 3 as i64;
+        let shard = sharder.pg_bigint_hash(key);
+        assert_eq!(shard, 1);
     }
 }