0022-Branchless-NibbleArray.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: md_5 <git@md-5.net>
Date: Sun, 31 Oct 2021 10:28:14 -0400
Subject: [PATCH] Branchless NibbleArray


diff --git a/src/main/java/net/minecraft/server/NibbleArray.java b/src/main/java/net/minecraft/server/NibbleArray.java
index 9306f97af94b6559dd28a3f942696ac4d3f6b746..a69c0bc8479d69ce9eefab48f13699d0402aa5cc 100644
--- a/src/main/java/net/minecraft/server/NibbleArray.java
+++ b/src/main/java/net/minecraft/server/NibbleArray.java
@@ -30,18 +30,16 @@ public class NibbleArray {
     public int a(int i) {
         int j = this.c(i);
 
-        return this.b(i) ? this.a[j] & 15 : this.a[j] >> 4 & 15;
+        return this.a[j] >> ((i & 1) << 2) & 15; // PandaSpigot
     }
 
     public void a(int i, int j) {
         int k = this.c(i);
 
-        if (this.b(i)) {
-            this.a[k] = (byte) (this.a[k] & 240 | j & 15);
-        } else {
-            this.a[k] = (byte) (this.a[k] & 15 | (j & 15) << 4);
-        }
-
+        // PandaSpigot start
+        int shift = (i & 1) << 2;
+        this.a[k] = (byte) (this.a[k] & ~(15 << shift) | (j & 15) << shift);
+        // PandaSpigot end
     }
 
     private boolean b(int i) {
diff --git a/src/test/java/org/bukkit/NibbleArrayTest.java b/src/test/java/org/bukkit/NibbleArrayTest.java
new file mode 100644
index 0000000000000000000000000000000000000000..448c29f17928bf25a4d44490684925d59fb46e27
--- /dev/null
+++ b/src/test/java/org/bukkit/NibbleArrayTest.java
@@ -0,0 +1,29 @@
+package org.bukkit;
+
+import java.util.Random;
+import net.minecraft.server.NibbleArray;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class NibbleArrayTest {
+    
+    private static final int NIBBLE_SIZE = 4096;
+    
+    @Test
+    public void testNibble() {
+        Random random = new Random();
+        byte[] classic = new byte[NIBBLE_SIZE];
+        NibbleArray nibble = new NibbleArray();
+        
+        for (int i = 0; i < classic.length; i++) {
+            byte number = (byte) (random.nextInt() & 0xF);
+            
+            classic[i] = number;
+            nibble.a(i, number);
+        }
+        
+        for (int i = 0; i < classic.length; i++) {
+            Assert.assertEquals("Nibble array mismatch", classic[i], nibble.a(i));
+        }
+    }
+}