From 55772dec318a8b571ba88506fd5f6ce82bc93d6b Mon Sep 17 00:00:00 2001
From: Jixun Wu <jixun.moe@gmail.com>
Date: Sat, 25 Dec 2021 12:07:14 +0000
Subject: [PATCH] feat(QMCv2): Allow extraction of songId from QMC2-wasm

(cherry picked from commit 9ca2d852ce713255caeb8424a2724cb936434f18)
---
 src/decrypt/qmc.ts      | 24 ++++++++++++++----------
 src/decrypt/qmc_wasm.ts | 33 +++++++++++++++++++++++++++++----
 2 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/src/decrypt/qmc.ts b/src/decrypt/qmc.ts
index d790d41..a04c901 100644
--- a/src/decrypt/qmc.ts
+++ b/src/decrypt/qmc.ts
@@ -3,6 +3,7 @@ import { AudioMimeType, GetArrayBuffer, SniffAudioExt } from '@/decrypt/utils';
 
 import { DecryptResult } from '@/decrypt/entity';
 import { QmcDeriveKey } from '@/decrypt/qmc_key';
+import { DecryptQMCWasm } from '@/decrypt/qmc_wasm';
 import { extractQQMusicMeta } from '@/utils/qm_meta';
 
 interface Handler {
@@ -41,17 +42,20 @@ export async function Decrypt(file: Blob, raw_filename: string, raw_ext: string)
 
   const fileBuffer = await GetArrayBuffer(file);
   let musicDecoded: Uint8Array | undefined;
-  let musicID: number | undefined;
+  let musicID: number | string | undefined;
 
-  // todo: wasm decoder doesn't support extract the song id for .mgg1/.mflac0 currently
-  // if (version === 2 && globalThis.WebAssembly) {
-  //   console.log('qmc: using wasm decoder');
-  //   const v2Decrypted = await DecryptQMCWasm(fileBuffer);
-  //   // 如果 v2 检测失败，降级到 v1 再尝试一次
-  //   if (v2Decrypted) {
-  //     musicDecoded = v2Decrypted;
-  //   }
-  // }
+  if (version === 2 && globalThis.WebAssembly) {
+    console.log('qmc: using wasm decoder');
+
+    const v2Decrypted = await DecryptQMCWasm(fileBuffer);
+    // 若 v2 检测失败，降级到 v1 再尝试一次
+    if (v2Decrypted.success) {
+      musicDecoded = v2Decrypted.data;
+      musicID = v2Decrypted.songId;
+    } else {
+      console.warn('qmc2-wasm failed with error %s', v2Decrypted.error || '(no error)');
+    }
+  }
 
   if (!musicDecoded) {
     // may throw error
diff --git a/src/decrypt/qmc_wasm.ts b/src/decrypt/qmc_wasm.ts
index bec030e..e83ead3 100644
--- a/src/decrypt/qmc_wasm.ts
+++ b/src/decrypt/qmc_wasm.ts
@@ -1,5 +1,6 @@
 import QMCCryptoModule from '@jixun/qmc2-crypto/QMC2-wasm-bundle';
 import { MergeUint8Array } from '@/utils/MergeUint8Array';
+import { QMCCrypto } from '@jixun/qmc2-crypto/QMCCrypto';
 
 // 检测文件末端使用的缓冲区大小
 const DETECTION_SIZE = 40;
@@ -7,14 +8,22 @@ const DETECTION_SIZE = 40;
 // 每次处理 2M 的数据
 const DECRYPTION_BUF_SIZE = 2 * 1024 * 1024;
 
+export interface QMC2DecryptionResult {
+  success: boolean;
+  data: Uint8Array;
+  songId: string | number;
+  error: string;
+}
+
 /**
  * 解密一个 QMC2 加密的文件。
  *
  * 如果检测并解密成功，返回解密后的 Uint8Array 数据。
  * @param  {ArrayBuffer} mggBlob 读入的文件 Blob
- * @return {Promise<Uint8Array|false>}
  */
-export async function DecryptQMCWasm(mggBlob: ArrayBuffer) {
+export async function DecryptQMCWasm(mggBlob: ArrayBuffer): Promise<QMC2DecryptionResult> {
+  const result: QMC2DecryptionResult = { success: false, data: new Uint8Array(), songId: 0, error: '' };
+
   // 初始化模组
   const QMCCrypto = await QMCCryptoModule();
 
@@ -34,12 +43,26 @@ export async function DecryptQMCWasm(mggBlob: ArrayBuffer) {
   const position = QMCCrypto.getValue(pDetectionResult, 'i32');
   const len = QMCCrypto.getValue(pDetectionResult + 4, 'i32');
 
+  result.success = detectOK;
+  result.error = QMCCrypto.UTF8ToString(
+    pDetectionResult + QMCCrypto.offsetof_error_msg(),
+    QMCCrypto.sizeof_error_msg(),
+  );
+  const songId = QMCCrypto.UTF8ToString(pDetectionResult + QMCCrypto.offsetof_song_id(), QMCCrypto.sizeof_song_id());
+  if (!songId) {
+    console.debug('qmc2-wasm: songId not found');
+  } else if (/^\d+$/.test(songId)) {
+    result.songId = songId;
+  } else {
+    console.warn('qmc2-wasm: Invalid songId: %s', songId);
+  }
+
   // 释放内存
   QMCCrypto._free(pDetectionBuf);
   QMCCrypto._free(pDetectionResult);
 
   if (!detectOK) {
-    return false;
+    return result;
   }
 
   // 计算解密后文件的大小。
@@ -75,5 +98,7 @@ export async function DecryptQMCWasm(mggBlob: ArrayBuffer) {
   QMCCrypto._free(buf);
   hCrypto.delete();
 
-  return MergeUint8Array(decryptedParts);
+  result.data = MergeUint8Array(decryptedParts);
+
+  return result;
 }