From 911e0e890febc00102cd1e5406731e66f7bad0ef Mon Sep 17 00:00:00 2001
From: LucienHH <66429271+LucienHH@users.noreply.github.com>
Date: Tue, 3 Dec 2024 22:23:32 +0000
Subject: [PATCH] Dynamic compression & batch header (#544)

---
 src/client.js            |  1 +
 src/connection.js        |  4 ++--
 src/server.js            |  4 ++++
 src/serverPlayer.js      |  2 ++
 src/transforms/framer.js | 11 +++++++----
 5 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/src/client.js b/src/client.js
index 87e3705..2d798e6 100644
--- a/src/client.js
+++ b/src/client.js
@@ -26,6 +26,7 @@ class Client extends Connection {
     this.compressionAlgorithm = this.versionGreaterThanOrEqualTo('1.19.30') ? 'none' : 'deflate'
     this.compressionThreshold = 512
     this.compressionLevel = this.options.compressionLevel
+    this.batchHeader = 0xfe
 
     if (isDebug) {
       this.inLog = (...args) => debug('C ->', ...args)
diff --git a/src/connection.js b/src/connection.js
index ca862ee..eb01f7f 100644
--- a/src/connection.js
+++ b/src/connection.js
@@ -153,7 +153,7 @@ class Connection extends EventEmitter {
 
   // These are callbacks called from encryption.js
   onEncryptedPacket = (buf) => {
-    const packet = Buffer.concat([Buffer.from([0xfe]), buf]) // add header
+    const packet = this.batchHeader ? Buffer.concat([Buffer.from([this.batchHeader]), buf]) : buf
     this.sendMCPE(packet)
   }
 
@@ -165,7 +165,7 @@ class Connection extends EventEmitter {
   }
 
   handle (buffer) { // handle encapsulated
-    if (buffer[0] === 0xfe) { // wrapper
+    if (!this.batchHeader || buffer[0] === this.batchHeader) { // wrapper
       if (this.encryptionEnabled) {
         this.decrypt(buffer.slice(1))
       } else {
diff --git a/src/server.js b/src/server.js
index 355e79a..6d9aa79 100644
--- a/src/server.js
+++ b/src/server.js
@@ -24,6 +24,7 @@ class Server extends EventEmitter {
     this.clients = {}
     this.clientCount = 0
     this.conLog = debug
+    this.batchHeader = 0xfe
 
     this.setCompressor(this.options.compressionAlgorithm, this.options.compressionLevel, this.options.compressionThreshold)
   }
@@ -44,16 +45,19 @@ class Server extends EventEmitter {
       case 'none':
         this.compressionAlgorithm = 'none'
         this.compressionLevel = 0
+        this.compressionHeader = 255
         break
       case 'deflate':
         this.compressionAlgorithm = 'deflate'
         this.compressionLevel = level
         this.compressionThreshold = threshold
+        this.compressionHeader = 0
         break
       case 'snappy':
         this.compressionAlgorithm = 'snappy'
         this.compressionLevel = level
         this.compressionThreshold = threshold
+        this.compressionHeader = 1
         break
       default:
         throw new Error(`Unknown compression algorithm: ${algorithm}`)
diff --git a/src/serverPlayer.js b/src/serverPlayer.js
index 4ef5243..b7ef02d 100644
--- a/src/serverPlayer.js
+++ b/src/serverPlayer.js
@@ -28,10 +28,12 @@ class Player extends Connection {
       this.outLog = (...args) => debug('<- S', ...args)
     }
 
+    this.batchHeader = this.server.batchHeader
     // Compression is server-wide
     this.compressionAlgorithm = this.server.compressionAlgorithm
     this.compressionLevel = this.server.compressionLevel
     this.compressionThreshold = this.server.compressionThreshold
+    this.compressionHeader = this.server.compressionHeader
 
     this._sentNetworkSettings = false // 1.19.30+
   }
diff --git a/src/transforms/framer.js b/src/transforms/framer.js
index c59dd4e..a2d9c4f 100644
--- a/src/transforms/framer.js
+++ b/src/transforms/framer.js
@@ -6,9 +6,11 @@ class Framer {
   constructor (client) {
     // Encoding
     this.packets = []
+    this.batchHeader = client.batchHeader
     this.compressor = client.compressionAlgorithm || 'none'
     this.compressionLevel = client.compressionLevel
     this.compressionThreshold = client.compressionThreshold
+    this.compressionHeader = client.compressionHeader || 0
     this.writeCompressor = client.features.compressorInHeader && client.compressionReady
   }
 
@@ -38,7 +40,7 @@ class Framer {
 
   static decode (client, buf) {
     // Read header
-    if (buf[0] !== 0xfe) throw Error('bad batch packet header ' + buf[0])
+    if (this.batchHeader && buf[0] !== this.batchHeader) throw Error(`bad batch packet header, received: ${buf[0]}, expected: ${this.batchHeader}`)
     const buffer = buf.slice(1)
     // Decompress
     let decompressed
@@ -58,9 +60,10 @@ class Framer {
 
   encode () {
     const buf = Buffer.concat(this.packets)
-    const compressed = (buf.length > this.compressionThreshold) ? this.compress(buf) : buf
-    const header = this.writeCompressor ? [0xfe, 0] : [0xfe]
-    return Buffer.concat([Buffer.from(header), compressed])
+    const shouldCompress = buf.length > this.compressionThreshold
+    const header = this.batchHeader ? [this.batchHeader] : []
+    if (this.writeCompressor) header.push(shouldCompress ? this.compressionHeader : 255)
+    return Buffer.concat([Buffer.from(header), shouldCompress ? this.compress(buf) : buf])
   }
 
   addEncodedPacket (chunk) {