feat: added support for ncm (#15)

src/decrypt-worker/crypto/ncm/ncm_pc.ts

@@ -0,0 +1,21 @@
+import { transformBlob } from '~/decrypt-worker/util/transformBlob';
+import type { CryptoBase } from '../CryptoBase';
+import { NCM_KEY, NCM_MAGIC_HEADER } from './ncm_pc.key';
+
+export class NCMCrypto implements CryptoBase {
+  cryptoName = 'NCM/PC';
+  checkByDecryptHeader = false;
+
+  async checkBySignature(buffer: ArrayBuffer) {
+    const view = new DataView(buffer, 0, NCM_MAGIC_HEADER.byteLength);
+    return NCM_MAGIC_HEADER.every((value, i) => value === view.getUint8(i));
+  }
+
+  async decrypt(buffer: ArrayBuffer): Promise<Blob> {
+    return transformBlob(buffer, (p) => p.make.NeteaseNCM(NCM_KEY));
+  }
+
+  public static make() {
+    return new NCMCrypto();
+  }
+}