Refactor the RLE compression of Serialiser 🗜️.

src/lib/serialiser/Serialiser.js

@@ -35,6 +35,41 @@ class Serialiser {
     }
   }
 
+  // Compress an array of data using the RLE compression algorithm.
+  compressArray(data) {
+    let n = 0;
+    while (n < data.length) {
+      let initialValue = data[n];
+      let loop = 0;
+
+      // Look 2 tiles ahead.
+      if (data[n] !== data[n + 1] || data[n] !== data[n + 2]) {
+        // The next 3 tiles are different. Count how many unique tiles there are.
+        // It stops once it encounters 3 identical tiles in a row.
+        const initialN = n;
+
+        do {
+          loop++;
+          initialValue = data[++n];
+        } while (initialValue !== data[n + 1] || initialValue !== data[n + 2]);
+
+        this.setUint8(loop | 0x80); // Set the type of loop.
+        for (let i = initialN; i < n; i++) {
+          this.setUint8(data[i]);
+        }
+      } else {
+        // The next 3 tiles are identical. Count how many of them in a row.
+        // It stops when it finds a different tile.
+        do {
+          loop++;
+        } while (initialValue === data[++n]);
+
+        this.setUint8(loop);
+        this.setUint8(initialValue);
+      }
+    }
+  }
+
   // Firefox doesn't support ArrayBuffer#resize.
   #resize(newByteLength) {
     if (ArrayBuffer.prototype.resize) {

src/lib/serialiser/room/serialiseRoomAttributes.js

@@ -1,12 +1,11 @@
 import Serialiser from '../Serialiser.js';
-import { compress } from '../serialiserUtils.js';
 
 const serialiseRoomAttributes = (attributes = [], width = 0) => {
   const serialiser = new Serialiser();
 
   const lineWidth = (width + 4) / 4; // 16 for 60px rooms, 8 for 28px rooms.
   for (let i = 0; i < 4; i++) {
-    compress(serialiser, attributes.slice(i * 16, i * 16 + lineWidth));
+    serialiser.compressArray(attributes.slice(i * 16, i * 16 + lineWidth));
   }
 
   return serialiser.buffer;

src/lib/serialiser/room/serialiseRoomNametable.js

@@ -1,11 +1,10 @@
 import Serialiser from '../Serialiser.js';
-import { compress } from '../serialiserUtils.js';
 
 const serialiseRoomNametable = (nametable = []) => {
   const serialiser = new Serialiser();
 
   for (let i = 0; i < nametable.length; i++) {
-    compress(serialiser, nametable[i].slice(2, 62));
+    serialiser.compressArray(nametable[i].slice(2, 62));
   }
 
   return serialiser.buffer;