如何以流的形式读写文件

import { fileIo as fs, ReadOptions } from '@kit.CoreFileKit';
import { common } from '@kit.AbilityKit';

// 获取应用文件路径
let context = getContext(this) as common.UIAbilityContext;
let filesDir = context.filesDir;

async function readWriteFileWithStream(): Promise<void> {
打开文件流
  let inputStream = fs.createStreamSync(filesDir + '/test.txt', 'r+');
  let outputStream = fs.createStreamSync(filesDir + '/destFile.txt', "w+");
以流的形式读取源文件内容并写入目的文件
  let bufSize = 4096;
  let readSize = 0;
  let buf = new ArrayBuffer(bufSize);
  let readOptions: ReadOptions = {
    offset: readSize,
    length: bufSize
  };
  let readLen = await inputStream.read(buf, readOptions);
  readSize += readLen;
  while (readLen > 0) {
    const writeBuf = readLen < bufSize ? buf.slice(0, readLen) : buf;
    await outputStream.write(writeBuf);
    readOptions.offset = readSize;
    readLen = await inputStream.read(buf, readOptions);
    readSize += readLen;
  }
关闭文件流
  inputStream.closeSync();
  outputStream.closeSync();
}
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