From 5170da8fd7d4287f6e3530a62b2070cd7901c8cc Mon Sep 17 00:00:00 2001
From: Andrew Steinborn <git@steinborn.me>
Date: Sun, 9 May 2021 02:57:01 -0400
Subject: [PATCH] Improve writeVarInt inlining by peeling the two most common
 cases

---
 .../proxy/protocol/ProtocolUtils.java             | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java b/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java
index ee3482c9d..7ae34b9db 100644
--- a/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java
+++ b/proxy/src/main/java/com/velocitypowered/proxy/protocol/ProtocolUtils.java
@@ -120,6 +120,19 @@ public enum ProtocolUtils {
    * @param value the integer to write
    */
   public static void writeVarInt(ByteBuf buf, int value) {
+    // 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 ((value & (0xFFFFFFFF << 7)) == 0) {
+      buf.writeByte(value);
+    } else if ((value & (0xFFFFFFFF << 14)) == 0) {
+      int w = (value & 0x7F | 0x80) << 8 | (value >>> 7);
+      buf.writeShort(w);
+    } else {
+      writeVarIntFull(buf, value);
+    }
+  }
+
+  private static void writeVarIntFull(ByteBuf buf, int value) {
     // See https://steinborn.me/posts/performance/how-fast-can-you-write-a-varint/
     if ((value & (0xFFFFFFFF << 7)) == 0) {
       buf.writeByte(value);
@@ -135,7 +148,7 @@ public enum ProtocolUtils {
       buf.writeInt(w);
     } else {
       int w = (value & 0x7F | 0x80) << 24 | ((value >>> 7) & 0x7F | 0x80) << 16
-          | ((value >>> 14) & 0x7F | 0x80) << 8 | ((value >>> 21) & 0x7F | 0x80);
+          | ((value >>> 14) & 0x7F | 0x80) | ((value >>> 21) & 0x7F | 0x80);
       buf.writeInt(w);
       buf.writeByte(value >>> 28);
     }