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; // 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 */ export async function DecryptQMCWasm(mggBlob: ArrayBuffer): Promise { const result: QMC2DecryptionResult = { success: false, data: new Uint8Array(), songId: 0, error: '' }; // 初始化模组 const QMCCrypto = await QMCCryptoModule(); // 申请内存块,并文件末端数据到 WASM 的内存堆 const detectionBuf = new Uint8Array(mggBlob.slice(-DETECTION_SIZE)); const pDetectionBuf = QMCCrypto._malloc(detectionBuf.length); QMCCrypto.writeArrayToMemory(detectionBuf, pDetectionBuf); // 检测结果内存块 const pDetectionResult = QMCCrypto._malloc(QMCCrypto.sizeof_qmc_detection()); // 进行检测 const detectOK = QMCCrypto.detectKeyEndPosition(pDetectionResult, pDetectionBuf, detectionBuf.length); // 提取结构体内容: // (pos: i32; len: i32; error: char[??]) 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 result; } // 计算解密后文件的大小。 // 之前得到的 position 为相对当前检测数据起点的偏移。 const decryptedSize = mggBlob.byteLength - DETECTION_SIZE + position; // 提取嵌入到文件的 EKey const ekey = new Uint8Array(mggBlob.slice(decryptedSize, decryptedSize + len)); // 解码 UTF-8 数据到 string const decoder = new TextDecoder(); const ekey_b64 = decoder.decode(ekey); // 初始化加密与缓冲区 const hCrypto = QMCCrypto.createInstWidthEKey(ekey_b64); const buf = QMCCrypto._malloc(DECRYPTION_BUF_SIZE); const decryptedParts = []; let offset = 0; let bytesToDecrypt = decryptedSize; while (bytesToDecrypt > 0) { const blockSize = Math.min(bytesToDecrypt, DECRYPTION_BUF_SIZE); // 解密一些片段 const blockData = new Uint8Array(mggBlob.slice(offset, offset + blockSize)); QMCCrypto.writeArrayToMemory(blockData, buf); QMCCrypto.decryptStream(hCrypto, buf, offset, blockSize); decryptedParts.push(QMCCrypto.HEAPU8.slice(buf, buf + blockSize)); offset += blockSize; bytesToDecrypt -= blockSize; } QMCCrypto._free(buf); hCrypto.delete(); result.data = MergeUint8Array(decryptedParts); return result; }