Paper/patches/server/0900-Optimize-VarInts.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: astei <andrew@steinborn.me>
Date: Sat, 28 Oct 2023 19:46:21 -0400
Subject: [PATCH] Optimize VarInts

https://github.com/PaperMC/Paper/pull/6957#issuecomment-985250854

diff --git a/src/main/java/net/minecraft/network/VarInt.java b/src/main/java/net/minecraft/network/VarInt.java
index 49a8ddc269d53458cfbd639b7de838c2e5765748..74ed47659d3e615c2dae7da98d5a8cf1559625bf 100644
--- a/src/main/java/net/minecraft/network/VarInt.java
+++ b/src/main/java/net/minecraft/network/VarInt.java
@@ -9,6 +9,18 @@ public class VarInt {
     private static final int DATA_BITS_PER_BYTE = 7;
 
     public static int getByteSize(int i) {
+    // Paper start - Optimize VarInts
+        return VARINT_EXACT_BYTE_LENGTHS[Integer.numberOfLeadingZeros(i)];
+    }
+    private static final int[] VARINT_EXACT_BYTE_LENGTHS = new int[33];
+    static {
+        for (int i = 0; i <= 32; ++i) {
+            VARINT_EXACT_BYTE_LENGTHS[i] = (int) Math.ceil((31d - (i - 1)) / 7d);
+        }
+        VARINT_EXACT_BYTE_LENGTHS[32] = 1; // Special case for the number 0.
+    }
+    public static int getByteSizeOld(int i) {
+    // Paper end - Optimize VarInts
         for (int j = 1; j < 5; j++) {
             if ((i & -1 << j * 7) == 0) {
                 return j;
@@ -39,6 +51,21 @@ public class VarInt {
     }
 
     public static ByteBuf write(ByteBuf buf, int i) {
+     // Paper start - Optimize VarInts
+        // Peel the one and two byte count cases explicitly as they are the most common VarInt sizes
+        // that the proxy will write, to improve inlining.
+        if ((i & (0xFFFFFFFF << 7)) == 0) {
+            buf.writeByte(i);
+        } else if ((i & (0xFFFFFFFF << 14)) == 0) {
+            int w = (i & 0x7F | 0x80) << 8 | (i >>> 7);
+            buf.writeShort(w);
+        } else {
+            writeOld(buf, i);
+        }
+        return buf;
+    }
+    public static ByteBuf writeOld(ByteBuf buf, int i) {
+    // Paper end - Optimize VarInts
         while ((i & -128) != 0) {
             buf.writeByte(i & 127 | 128);
             i >>>= 7;