Merge pull request '优化 QMCCache 解密过程' (#6) from jixunmoe/um-web:refactor/optimise-qm-cache-decode into master

Reviewed-on: https://git.unlock-music.dev/um/web/pulls/6

src/decrypt/__test__/QmcCache.test.ts

@@ -0,0 +1,20 @@
+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

@@ -1,50 +1,52 @@
-import {
-  AudioMimeType,
-  GetArrayBuffer,
-  GetCoverFromFile,
-  GetMetaFromFile,
-  SniffAudioExt,
-  SplitFilename,
-} from '@/decrypt/utils';
-
-import { Decrypt as QmcDecrypt, HandlerMap } from '@/decrypt/qmc';
-
-import { DecryptResult } from '@/decrypt/entity';
-
-import { parseBlob as metaParseBlob } from 'music-metadata-browser';
-
-export async function Decrypt(file: Blob, raw_filename: string, _: string): Promise<DecryptResult> {
-  const buffer = new Uint8Array(await GetArrayBuffer(file));
-  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;
-  if (ext !== '' || newName.ext === 'mp3') {
-    audioBlob = new Blob([buffer], { type: AudioMimeType[ext] });
-  } else if (newName.ext in HandlerMap) {
-    audioBlob = new Blob([buffer], { type: 'application/octet-stream' });
-    return QmcDecrypt(audioBlob, newName.name, newName.ext);
-  } else {
-    throw '不支持的QQ音乐缓存格式';
-  }
-  const tag = await metaParseBlob(audioBlob);
-  const { title, artist } = GetMetaFromFile(raw_filename, tag.common.title, tag.common.artist);
-
-  return {
-    title,
-    artist,
-    ext,
-    album: tag.common.album,
-    picture: GetCoverFromFile(tag),
-    file: URL.createObjectURL(audioBlob),
-    blob: audioBlob,
-    mime: AudioMimeType[ext],
-  };
-}
+import {
+  AudioMimeType,
+  GetArrayBuffer,
+  GetCoverFromFile,
+  GetMetaFromFile,
+  SniffAudioExt,
+  SplitFilename,
+} from '@/decrypt/utils';
+
+import { Decrypt as QmcDecrypt, HandlerMap } from '@/decrypt/qmc';
+
+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 ext = SniffAudioExt(buffer, '');
+  const newName = SplitFilename(raw_filename);
+  let audioBlob: Blob;
+  if (ext !== '' || newName.ext === 'mp3') {
+    audioBlob = new Blob([buffer], { type: AudioMimeType[ext] });
+  } else if (newName.ext in HandlerMap) {
+    audioBlob = new Blob([buffer], { type: 'application/octet-stream' });
+    return QmcDecrypt(audioBlob, newName.name, newName.ext);
+  } else {
+    throw '不支持的QQ音乐缓存格式';
+  }
+  const tag = await metaParseBlob(audioBlob);
+  const { title, artist } = GetMetaFromFile(raw_filename, tag.common.title, tag.common.artist);
+
+  return {
+    title,
+    artist,
+    ext,
+    album: tag.common.album,
+    picture: GetCoverFromFile(tag),
+    file: URL.createObjectURL(audioBlob),
+    blob: audioBlob,
+    mime: AudioMimeType[ext],
+  };
+}