From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Martijn Muijsers <martijnmuijsers@live.nl>
Date: Mon, 21 Aug 2023 21:46:10 +0200
Subject: [PATCH] Pre-compute VarLong sizes

License: GPL-3.0 (https://www.gnu.org/licenses/gpl-3.0.html)
Gale - https://galemc.org

This patch is based on the following commit:
"Reapply "Optimize varint writing""
By: Andrew Steinborn <git@steinborn.me>
As part of: Velocity (https://github.com/PaperMC/Velocity)
Licensed under: GPL-3.0 (https://www.gnu.org/licenses/gpl-3.0.html)

* Velocity description *

Inspired by the approach described at the bottom of https://richardstartin.github.io/posts/dont-use-protobuf-for-telemetry

Given that we do a lot of varint writing as well, this should provide a small performance boost for larger/complex packets whilst not regressing hard on smaller packets.

This includes a test to ensure that the behavior is as expected and fixes the initialization loop so that the correct results will be given. Much thanks to @octylFractal for acting as my duck while trying to figure this out.

diff --git a/net/minecraft/network/VarLong.java b/net/minecraft/network/VarLong.java
index df9a85b19a9767c85f02837af6835f7ddb6c7dc3..ff9d84bf761797a8f695926c3cbb12c07609365d 100644
--- a/net/minecraft/network/VarLong.java
+++ b/net/minecraft/network/VarLong.java
@@ -9,6 +9,18 @@ public class VarLong {
     private static final int DATA_BITS_PER_BYTE = 7;
 
     public static int getByteSize(long data) {
+        // Gale start - Velocity - pre-compute VarInt and VarLong sizes
+        return VARLONG_EXACT_BYTE_LENGTHS[Long.numberOfLeadingZeros(data)];
+    }
+    private static final int[] VARLONG_EXACT_BYTE_LENGTHS = new int[65];
+    static {
+        for (int i = 0; i < 64; ++i) {
+            VARLONG_EXACT_BYTE_LENGTHS[i] = (int) Math.ceil((63d - (i - 1)) / 7d);
+        }
+        VARLONG_EXACT_BYTE_LENGTHS[64] = 1; // Special case for the number 0
+    }
+    static int getByteSizeOld(long data) { // public -> package-private
+        // Gale end - Velocity - pre-compute VarInt and VarLong sizes
         for (int i = 1; i < 10; i++) {
             if ((data & -1L << i * 7) == 0L) {
                 return i;