web/src/decrypt/xm.ts

import { Decrypt as RawDecrypt } from '@/decrypt/raw';
import { DecryptResult } from '@/decrypt/entity';
import { AudioMimeType, BytesHasPrefix, GetArrayBuffer, GetCoverFromFile, GetMetaFromFile } from '@/decrypt/utils';

import { parseBlob as metaParseBlob } from 'music-metadata-browser';

const MagicHeader = [0x69, 0x66, 0x6d, 0x74];
const MagicHeader2 = [0xfe, 0xfe, 0xfe, 0xfe];
const FileTypeMap: { [key: string]: string } = {
  ' WAV': '.wav',
  FLAC: '.flac',
  ' MP3': '.mp3',
  ' A4M': '.m4a',
};

export async function Decrypt(file: File, raw_filename: string, raw_ext: string): Promise<DecryptResult> {
  const oriData = new Uint8Array(await GetArrayBuffer(file));
  if (!BytesHasPrefix(oriData, MagicHeader) || !BytesHasPrefix(oriData.slice(8, 12), MagicHeader2)) {
    if (raw_ext === 'xm') {
      throw Error('此xm文件已损坏');
    } else {
      return await RawDecrypt(file, raw_filename, raw_ext, true);
    }
  }

  let typeText = new TextDecoder().decode(oriData.slice(4, 8));
  if (!FileTypeMap.hasOwnProperty(typeText)) {
    throw Error('未知的.xm文件类型');
  }

  let key = oriData[0xf];
  let dataOffset = oriData[0xc] | (oriData[0xd] << 8) | (oriData[0xe] << 16);
  let audioData = oriData.slice(0x10);
  let lenAudioData = audioData.length;
  for (let cur = dataOffset; cur < lenAudioData; ++cur) audioData[cur] = (audioData[cur] - key) ^ 0xff;

  const ext = FileTypeMap[typeText];
  const mime = AudioMimeType[ext];
  let musicBlob = new Blob([audioData], { type: mime });

  const musicMeta = await metaParseBlob(musicBlob);
  if (ext === 'wav') {
    //todo:未知的编码方式
    console.info(musicMeta.common);
    musicMeta.common.album = '';
    musicMeta.common.artist = '';
    musicMeta.common.title = '';
  }
  const { title, artist } = GetMetaFromFile(
    raw_filename,
    musicMeta.common.title,
    musicMeta.common.artist,
    raw_filename.indexOf('_') === -1 ? '-' : '_',
  );

  return {
    title,
    artist,
    ext,
    mime,
    album: musicMeta.common.album,
    picture: GetCoverFromFile(musicMeta),
    file: URL.createObjectURL(musicBlob),
    blob: musicBlob,
    rawExt: 'xm',
  };
}