From 7df26af3e3750d915496365e511828fcac365497 Mon Sep 17 00:00:00 2001
From: Heorhii <margievge@gmail.com>
Date: Wed, 8 Nov 2023 15:20:38 +0100
Subject: [PATCH] Rewrite class Frame

---
 lib/websocket.js | 90 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 88 insertions(+), 2 deletions(-)

diff --git a/lib/websocket.js b/lib/websocket.js
index 09f6884b..80b4bfac 100644
--- a/lib/websocket.js
+++ b/lib/websocket.js
@@ -26,6 +26,91 @@ const DEFAULT_OPTIONS = {
 const xor = (cond1, cond2) => (cond1 || cond2) && !(cond1 && cond2);
 
 class Frame {
+  #frame = null;
+  #masked = null;
+  #dataOffset = null;
+  #mask = null;
+  #length = null;
+
+  constructor(frame) {
+    this.#frame = frame;
+    const length = BigInt(this.#frame[1] & 0x7f);
+    this.#masked = true;
+    switch (length) {
+      case 127n:
+        this.#dataOffset = 2 + 8 + MASK_LENGTH;
+        this.#mask = frame.subarray(2 + 8, 10 + MASK_LENGTH);
+        this.#length = frame.readBigUInt64BE(2);
+        break;
+      case 126n:
+        this.#dataOffset = 2 + 2 + MASK_LENGTH;
+        this.#mask = frame.subarray(2 + 2, 4 + MASK_LENGTH);
+        this.#length = BigInt(this.#frame.readUInt16BE(2));
+        break;
+      default:
+        this.#dataOffset = 2 + MASK_LENGTH;
+        this.#mask = frame.subarray(2, 2 + MASK_LENGTH);
+        this.#length = length;
+    }
+  }
+
+  unmask() {
+    if (!this.#masked) return;
+    for (let i = 0n; i < this.#length; ++i) {
+      this.#frame[BigInt(this.#dataOffset) + i] ^=
+        this.#mask[i & 0x0000000000000003n];
+    }
+  }
+
+  toString() {
+    return this.#frame.toString(
+      'utf8',
+      this.#dataOffset,
+      Number(BigInt(this.#dataOffset) + this.#length),
+    );
+  }
+
+  get frame() {
+    return this.#frame;
+  }
+
+  static from(data) {
+    if (Buffer.isBuffer(data)) {
+      if (data.length === 0) throw new Error('Empty frame!');
+      // let invalidStructureCheck = false;
+      if ((data[1] & 0x80) !== 0x80) throw new Error('1002: protocol error');
+      return new Frame(data);
+    }
+
+    if (typeof data === 'string') {
+      if (data.length === 0) throw new Error('Empty string!');
+      const payload = Buffer.from(data);
+      const length = payload.length;
+      let meta = Buffer.alloc(2);
+      meta[0] = 0x81; // FIN = 1, RSV = 0b000, opcode = 0b0001 (text frame)
+      if (length < LEN_16_BIT) {
+        meta[1] = length;
+      } else if (length < MAX_16_BIT) {
+        const len = Buffer.alloc(2);
+        len.writeUint16BE(length, 0);
+        meta[1] = LEN_16_BIT;
+        meta = Buffer.concat([meta, len]);
+      } else if (length < MAX_64_BIT) {
+        const len = Buffer.alloc(8);
+        len.writeBigUInt64BE(BigInt(length), 0);
+        meta[1] = LEN_64_BIT;
+        this.meta = Buffer.concat([meta, len]);
+      } else {
+        throw new Error('string is too long to encode in one frame!');
+      }
+      const frame = Buffer.concat([meta, payload]);
+      return new Frame(Buffer.from(frame));
+    }
+
+    throw new Error('Unsupported');
+  }
+}
+class FrameO {
   #frame = null;
   #mask = null;
   #dataOffset = 6;
@@ -147,14 +232,15 @@ class Connection {
   }
 
   send(text) {
-    const frame = new Frame(text);
+    const frame = Frame.from(text);
     this.socket.write(frame.frame);
   }
 
   receive(data) {
     console.log('data: ', data[0], data.length);
     if (data[0] !== OPCODE_SHORT) return;
-    const frame = new Frame(data);
+    const frame = Frame.from(data);
+    frame.unmask();
     const text = frame.toString();
     console.log('Message:', text);
     this.send(`Echo "${text}"`);