src/decrypt/__test__/QmcCache.test.ts

@@ -1,20 +0,0 @@
-import { DecryptBuffer as DecryptQmcCacheBuffer } from '../qmccache';
-import fs from 'fs';
-
-const expectedBuffer = fs.readFileSync(__dirname + '/fixture/qmc_cache_expected.bin');
-
-const createInputBuffer = () => {
-  const buffer = Buffer.alloc(256);
-  for (let i = buffer.byteLength; i >= 0; i--) {
-    buffer[i] = i;
-  }
-  return buffer;
-};
-
-describe('decrypt/qmccache', () => {
-  it('should decrypt specified buffer correctly', () => {
-    const input = createInputBuffer();
-    DecryptQmcCacheBuffer(input);
-    expect(input).toEqual(expectedBuffer);
-  });
-});

src/decrypt/qmccache.ts

@@ -13,18 +13,16 @@ import { DecryptResult } from '@/decrypt/entity';
 
 import { parseBlob as metaParseBlob } from 'music-metadata-browser';
 
-export function DecryptBuffer(buffer: Uint8Array | Buffer) {
-  let length = buffer.byteLength;
-  for (let i = 0; i < length; i++) {
-    let byte = buffer[i] ^ 0xf4; // xor 0xf4
-    byte = ((byte & 0b0011_1111) << 2) | (byte >> 6); // rol 2
-    buffer[i] = byte;
-  }
-}
-
 export async function Decrypt(file: Blob, raw_filename: string, _: string): Promise<DecryptResult> {
   const buffer = new Uint8Array(await GetArrayBuffer(file));
-  DecryptBuffer(buffer);
+  let length = buffer.length;
+  for (let i = 0; i < length; i++) {
+    buffer[i] ^= 0xf4;
+    if (buffer[i] <= 0x3f) buffer[i] = buffer[i] * 4;
+    else if (buffer[i] <= 0x7f) buffer[i] = (buffer[i] - 0x40) * 4 + 1;
+    else if (buffer[i] <= 0xbf) buffer[i] = (buffer[i] - 0x80) * 4 + 2;
+    else buffer[i] = (buffer[i] - 0xc0) * 4 + 3;
+  }
   let ext = SniffAudioExt(buffer, '');
   const newName = SplitFilename(raw_filename);
   let audioBlob: Blob;