HarmonyOS如何高效拷贝rawfile下面的文件到files目录下

import fs from '@ohos.file.fs'; 
@Entry 
@Component 
struct TestError { 
  @State message: string = 'Hello World' 
  @State rawfilePath:string = "config.txt"; 
  build() { 
    Row() { 
      Column() { 
        Text(this.message) 
          .fontSize(50) 
          .fontWeight(FontWeight.Bold) 
 
        Button(`将文件${this.rawfilePath}复制`) 
          .fontSize(16) 
          .fontWeight(FontWeight.Bold) 
          .margin(5) 
          .onClick(() => { 
            getContext(this).resourceManager.getRawFd(this.rawfilePath).then(file => { 
              this.copy2file(file) 
            }).catch((err) => { 
              console.log(JSON.stringify(err)); 
            }) 
          }) 
      } 
      .width('100%') 
    } 
    .height('100%') 
  } 
  async copy2file(item) { 
    try { 
      let dstPath = getContext(this).filesDir+'/test.txt' 
      this.saveFileToCache(item, dstPath) 
    } catch(e) { 
      console.log(`RawFile#copy2file() error : ${JSON.stringify(e)}`) 
    } 
  } 
  saveFileToCache(file, path) { 
    // 创建缓存文件(当前是覆盖式创建) 
    let cacheFile = fs.openSync( 
      path, 
      fs.OpenMode.WRITE_ONLY | fs.OpenMode.CREATE | fs.OpenMode.TRUNC) 
    let buffer = new ArrayBuffer(4096); 
    let currentOffset = file.offset; 
    let lengthNeedToReed = file.length; 
    let readOption = { 
      offset: currentOffset, 
      length: lengthNeedToReed > buffer.byteLength ? 4096 : lengthNeedToReed 
    } 
    while(true) { 
      // 读取buffer容量的内容 
      let readLength = fs.readSync(file.fd, buffer, readOption); 
      // 写入buffer容量的内容 
      fs.writeSync(cacheFile.fd, buffer, {length:readLength}) 
      // 判断后续内容 修改读文件的参数 
      if (readLength < 4096) { 
        break; 
      } 
      lengthNeedToReed -= readLength; 
      readOption.offset += readLength; 
      readOption.length = lengthNeedToReed > buffer.byteLength ? 4096 : lengthNeedToReed; 
    } 
    fs.close(cacheFile); 
  } 
}
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