feat(Utils): Add UMP parser

Currently not used anywhere in the project, but I figured I'd add it in case anyone wants to make their playback requests look more genuine by using UMP/SABR.

src/utils/UMP.ts

@@ -0,0 +1,60 @@
+export interface UMPPart {
+  type: number;
+  size: number;
+  data: Uint8Array;
+}
+
+export default class UMP {
+  buffer: Uint8Array;
+  offset: number;
+
+  constructor(buffer: Uint8Array) {
+    this.buffer = buffer;
+    this.offset = 0;
+  }
+
+  readVarInt(): number {
+    const prefix = this.buffer[this.offset];
+    const size = this.varintSize(prefix);
+    let result = 0;
+    let shift = 0;
+
+    if (size !== 5) {
+      shift = 8 - size;
+      const mask = (1 << shift) - 1;
+      result |= prefix & mask;
+    }
+
+    for (let i = 1; i < size; i++) {
+      const byte = this.buffer[this.offset + i];
+      result |= byte << shift;
+      shift += 8;
+    }
+
+    this.offset += size;
+    return result;
+  }
+
+  varintSize(byte: number): number {
+    let lo = 0;
+    for (let i = 7; i >= 4; i--) {
+      if (byte & (1 << i)) lo++;
+      else break;
+    }
+    return Math.min(lo + 1, 5);
+  }
+
+  parse(): UMPPart[] {
+    const parts = [];
+
+    while (this.offset < this.buffer.length) {
+      const part_type = this.readVarInt();
+      const part_size = this.readVarInt();
+      const part_data = this.buffer.slice(this.offset, this.offset + part_size);
+      this.offset += part_size;
+      parts.push({ type: part_type, size: part_size, data: part_data });
+    }
+
+    return parts;
+  }
+}

src/utils/index.ts

@@ -13,4 +13,7 @@ export { Platform } from './Utils.js';
 export * as Utils from './Utils.js';
 
 export { default as Log } from './Log.js';
-export * as LZW from './LZW.js';
+export * as LZW from './LZW.js';
+
+export { default as UMP } from './UMP.js';
+export * from './UMP.js';