using proper hashing function

2026-03-09 13:21:51 +09:00 · 2020-02-24 14:45:12 +09:00
parent 73775d9148
commit 0d8d6ca9fa
4 changed files with 109 additions and 4 deletions
--- a/src/net/torvald/random/XXHash32.java
+++ b/src/net/torvald/random/XXHash32.java
@@ -0,0 +1,79 @@
+package net.torvald.random;
+
+import net.torvald.UnsafeHelper;
+import net.torvald.terrarum.AppLoader;
+
+/**
+ * Code from https://richardstartin.github.io/posts/xxhash
+ * https://github.com/richardstartin/xxhash-benchmark
+ * Created by minjaesong on 2020-02-24
+ */
+
+public class XXHash32 {
+
+    static final int PRIME1 = 0x9E3779B1;
+    static final int PRIME2 = 0x85EBCA77;
+    static final int PRIME3 = 0xC2B2AE3D;
+    static final int PRIME4 = 0x27D4EB2F;
+    static final int PRIME5 = 0x165667B1;
+
+    static final int ARRAY_ELEM_OFFSET = (AppLoader.is32BitJVM) ? 8 : 16;
+
+    public static int hash(byte[] data, int seed) {
+        int end = data.length;
+        int offset = 0;
+        int h32;
+        if (data.length >= 16) {
+            int limit = end - 16;
+            int v1 = seed + PRIME1 + PRIME2;
+            int v2 = seed + PRIME2;
+            int v3 = seed;
+            int v4 = seed - PRIME1;
+
+            do {
+                v1 += getInt(data, offset) * PRIME2;
+                v1 = Integer.rotateLeft(v1, 13);
+                v1 *= PRIME1;
+                offset += 4;
+                v2 += getInt(data, offset) * PRIME2;
+                v2 = Integer.rotateLeft(v2, 13);
+                v2 *= PRIME1;
+                offset += 4;
+                v3 += getInt(data, offset) * PRIME2;
+                v3 = Integer.rotateLeft(v3, 13);
+                v3 *= PRIME1;
+                offset += 4;
+                v4 += getInt(data, offset) * PRIME2;
+                v4 = Integer.rotateLeft(v4, 13);
+                v4 *= PRIME1;
+                offset += 4;
+            } while(offset <= limit);
+
+            h32 = Integer.rotateLeft(v1, 1) + Integer.rotateLeft(v2, 7) + Integer.rotateLeft(v3, 12) + Integer.rotateLeft(v4, 18);
+        } else {
+            h32 = seed + PRIME5;
+        }
+
+        for(h32 += data.length; offset <= end - 4; offset += 4) {
+            h32 += getInt(data, offset) * PRIME3;
+            h32 = Integer.rotateLeft(h32, 17) * PRIME4;
+        }
+
+        while(offset < end) {
+            h32 += (data[offset] & 255) * PRIME5;
+            h32 = Integer.rotateLeft(h32, 11) * PRIME1;
+            ++offset;
+        }
+
+        h32 ^= h32 >>> 15;
+        h32 *= PRIME2;
+        h32 ^= h32 >>> 13;
+        h32 *= PRIME3;
+        h32 ^= h32 >>> 16;
+        return h32;
+    }
+
+    protected static int getInt(byte[] data, int offset) {
+        return UnsafeHelper.INSTANCE.getUnsafe().getInt(data, offset + ARRAY_ELEM_OFFSET);
+    }
+}