HarmonyOS 鸿蒙Next websocket的send方法里把.mp3音频文件转成ArrayBuffer发过去

可以将文件转换成buferArray的数组 然后转成Base64的字符串 在使用加解密进行解密
但是这个方法只能用以鸿蒙本地的加解密 跨服务的话无法使用 因为android ios 使用的有符号数组-128=> 127 而鸿蒙是0 =>255
所以跨服 使得字符数组所代表的意义不同 无法转换还原
读取文件转换为buferArray的数组的代码demo实例如下

import { BusinessError } from '[@ohos](/user/ohos).base';
import buffer from '[@ohos](/user/ohos).buffer';
let filePath = pathDir + "/test.txt";
let file = fs.openSync(filePath, fs.OpenMode.READ_WRITE);
let arrayBuffer = new ArrayBuffer(4096);//指定长度的与arrayBuffer
//从文件读取数据buf
fs.read(file.fd, arrayBuffer, (err: BusinessError, readLen: number) => {
  if (err) {
    console.error("read failed with error message: " + err.message + ", error code: " + err.code);
  } else {
    console.info("read file data succeed");
    let buf = buffer.from(arrayBuffer, 0, readLen);
    console.info(`The content of file: ${buf.toString()}`);
  }
  fs.closeSync(file);
}); 

参考链接：https://developer.huawei.com/consumer/cn/doc/harmonyos-references-V5/js-apis-file-fs-V5#fsread
ArrayBuffer最大长度就是4096 对于一整个文件 没办法读取完整
可以在每次读取之后使用[@ohos](/user/ohos).buffer (Buffer)中的Buffer对象存储本次读取的值 在全部读取完成后 使用buffer.concat()合并所有Buffer的内容 demo参考如下：

async readLocalFileWithStream() {
    try {
      // 存储每次读取的结果
      let buffers: buffer.Buffer[] = [];
      // 打开文件流
      let inputStream = fs.createStreamSync("文件沙箱路径", 'r+');
      // 以流的形式读取源文件内容
      let bufSize = 4096;
      let readSize = 0;
      let buf = new ArrayBuffer(bufSize);
      class Option {
        public offset: number = 0;
        public length: number = bufSize;
      }
      let option = new Option();
      option.offset = readSize;
      let readLen = await inputStream.read(buf, option);
      // 存储当前读取结果
      buffers.push(buffer.from(buf.slice(0, readLen)))
      readSize += readLen;
      while (readLen > 0) {
        option.offset = readSize;
        readLen = await inputStream.read(buf, option);
        // 存储当前读取结果
        buffers.push(buffer.from(buf.slice(0, readLen)))
        readSize += readLen;
      }
      // 关闭文件流
      inputStream.closeSync();
      // 合并内容
      let finalBuf: ArrayBuffer = buffer.concat(buffers).buffer
      console.info(`final ArrayBuffer byteLength is ${finalBuf.byteLength}}`)
    } catch (error) {
      let err = error as BusinessError;
      console.error(`readLocalFileWithStream failed, code is ${err.code},message is ${err.message}`);
    }
  }