um-react/src/decrypt-worker/decipher/Migu3d.ts

import { DecipherInstance, DecipherOK, DecipherResult, Status } from '~/decrypt-worker/Deciphers.ts';
import { chunkBuffer } from '~/decrypt-worker/util/buffer.ts';
import { Migu3D } from '@unlock-music/crypto';

export class Migu3DKeylessDecipher implements DecipherInstance {
  cipherName = 'Migu3D (Keyless)';

  async decrypt(buffer: Uint8Array): Promise<DecipherResult | DecipherOK> {
    const mg3d = Migu3D.fromHeader(buffer.subarray(0, 0x100));
    const audioBuffer = new Uint8Array(buffer);

    for (const [block, i] of chunkBuffer(audioBuffer)) {
      mg3d.decrypt(block, i);
    }
    mg3d.free();

    return {
      cipherName: this.cipherName,
      status: Status.OK,
      data: audioBuffer,
    };
  }

  public static make() {
    return new Migu3DKeylessDecipher();
  }
}