From dc381b72c6b2f8172001dedd84116122e4cc95b3 Mon Sep 17 00:00:00 2001
From: Damien Arrachequesne <damien.arrachequesne@gmail.com>
Date: Mon, 10 May 2021 11:05:28 +0200
Subject: [PATCH] perf: add support for the "wsPreEncoded" writing option

Packets that are sent to multiple clients will now be pre-encoded for
the WebSocket transport (which means simply prepending "4" - which is
the "message" packet type in Engine.IO).

Note: buffers are not pre-encoded, since they are sent without
modification over the WebSocket connection

See also: https://github.com/socketio/engine.io/commit/7706b123df914777d19c8179b45ab6932f82916c

engine.io diff: https://github.com/socketio/engine.io/compare/5.0.0...5.1.0
---
 lib/client.ts     | 47 +++++++++++++++++++++++++----------------------
 package-lock.json | 12 ++++++------
 package.json      |  4 ++--
 test/socket.io.ts | 22 ++++++++++++++++++++++
 4 files changed, 55 insertions(+), 30 deletions(-)

diff --git a/lib/client.ts b/lib/client.ts
index 7d4ef9151e..3693744cce 100644
--- a/lib/client.ts
+++ b/lib/client.ts
@@ -10,6 +10,12 @@ import type { SocketId } from "socket.io-adapter";
 
 const debug = debugModule("socket.io:client");
 
+interface WriteOptions {
+  compress?: boolean;
+  volatile?: boolean;
+  wsPreEncoded?: string;
+}
+
 export class Client<
   ListenEvents extends EventsMap,
   EmitEvents extends EventsMap
@@ -180,31 +186,28 @@ export class Client<
    * @param {Object} opts
    * @private
    */
-  _packet(packet: Packet, opts?: any): void {
-    opts = opts || {};
-    const self = this;
-
-    // this writes to the actual connection
-    function writeToEngine(encodedPackets: any) {
-      // TODO clarify this.
-      if (opts.volatile && !self.conn.transport.writable) return;
-      for (let i = 0; i < encodedPackets.length; i++) {
-        self.conn.write(encodedPackets[i], { compress: opts.compress });
-      }
+  _packet(packet: Packet, opts: WriteOptions = {}): void {
+    if (this.conn.readyState !== "open") {
+      debug("ignoring packet write %j", packet);
+      return;
+    }
+    const encodedPackets = this.encoder.encode(packet);
+    for (const encodedPacket of encodedPackets) {
+      this.writeToEngine(encodedPacket, opts);
     }
+  }
 
-    if ("open" === this.conn.readyState) {
-      debug("writing packet %j", packet);
-      if (!opts.preEncoded) {
-        // not broadcasting, need to encode
-        writeToEngine(this.encoder.encode(packet)); // encode, then write results to engine
-      } else {
-        // a broadcast pre-encodes a packet
-        writeToEngine(packet);
-      }
-    } else {
-      debug("ignoring packet write %j", packet);
+  private writeToEngine(
+    encodedPacket: String | Buffer,
+    opts: WriteOptions
+  ): void {
+    if (opts.volatile && !this.conn.transport.writable) {
+      debug(
+        "volatile packet is discarded since the transport is not currently writable"
+      );
+      return;
     }
+    this.conn.write(encodedPacket, opts);
   }
 
   /**
diff --git a/package-lock.json b/package-lock.json
index 48a47caf31..0aeea39007 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1206,9 +1206,9 @@
       }
     },
     "engine.io": {
-      "version": "5.0.0",
-      "resolved": "https://registry.npmjs.org/engine.io/-/engine.io-5.0.0.tgz",
-      "integrity": "sha512-BATIdDV3H1SrE9/u2BAotvsmjJg0t1P4+vGedImSs1lkFAtQdvk4Ev1y4LDiPF7BPWgXWEG+NDY+nLvW3UrMWw==",
+      "version": "5.1.0",
+      "resolved": "https://registry.npmjs.org/engine.io/-/engine.io-5.1.0.tgz",
+      "integrity": "sha512-A2i4kVvOA3qezQLlMz+FayGFdqOo0LP3fYrb0VqXMDXKoXcbgM0KxcEYnsdVzOMJQErIAb1GIStRj7UWFoiqlQ==",
       "requires": {
         "accepts": "~1.3.4",
         "base64id": "2.0.0",
@@ -3330,9 +3330,9 @@
       }
     },
     "socket.io-adapter": {
-      "version": "2.2.0",
-      "resolved": "https://registry.npmjs.org/socket.io-adapter/-/socket.io-adapter-2.2.0.tgz",
-      "integrity": "sha512-rG49L+FwaVEwuAdeBRq49M97YI3ElVabJPzvHT9S6a2CWhDKnjSFasvwAwSYPRhQzfn4NtDIbCaGYgOCOU/rlg=="
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/socket.io-adapter/-/socket.io-adapter-2.3.0.tgz",
+      "integrity": "sha512-jdIbSFRWOkaZpo5mXy8T7rXEN6qo3bOFuq4nVeX1ZS7AtFlkbk39y153xTXEIW7W94vZfhVOux1wTU88YxcM1w=="
     },
     "socket.io-client": {
       "version": "4.0.2",
diff --git a/package.json b/package.json
index 1ae020879c..5f62de0bf6 100644
--- a/package.json
+++ b/package.json
@@ -51,8 +51,8 @@
     "accepts": "~1.3.4",
     "base64id": "~2.0.0",
     "debug": "~4.3.1",
-    "engine.io": "~5.0.0",
-    "socket.io-adapter": "~2.2.0",
+    "engine.io": "~5.1.0",
+    "socket.io-adapter": "~2.3.0",
     "socket.io-parser": "~4.0.3"
   },
   "devDependencies": {
diff --git a/test/socket.io.ts b/test/socket.io.ts
index 48f4a76cee..84c57d1acb 100644
--- a/test/socket.io.ts
+++ b/test/socket.io.ts
@@ -2385,6 +2385,28 @@ describe("socket.io", () => {
         });
       });
     });
+
+    it("should pre encode a broadcast packet", (done) => {
+      const srv = createServer();
+      const sio = new Server(srv);
+
+      srv.listen(() => {
+        const clientSocket = client(srv, { multiplex: false });
+
+        sio.on("connection", (socket) => {
+          socket.conn.on("packetCreate", (packet) => {
+            expect(packet.data).to.eql('2["hello","world"]');
+            expect(packet.options.wsPreEncoded).to.eql('42["hello","world"]');
+
+            clientSocket.close();
+            sio.close();
+            done();
+          });
+
+          sio.emit("hello", "world");
+        });
+      });
+    });
   });
 
   describe("middleware", () => {