// 小文件本地路径转化成File文件流
async handleClick () {
      const { canceled, filePaths } = await remote.dialog.showOpenDialog({
        properties: ['openFile']
      })
      if (!canceled) {
        // filePaths[0]   C://xxxxx/a.png
        const { size } = fs.statSync(filePaths[0])
        //  文件上传大小限制  524288000
        if (size >= 524288000) {
          this.$message.warning('上传文件不能超过500M')
        } else {
           // 文件本地路径
          this.uploadPath = filePaths[0]
          // 文件名
          const name = path.basename(item)
         //  此方法适应于小文件转换
          const buffer = fs.readFileSync(this.uploadPath)
          const blob = new Blob([buffer])
          this.fileStream = new File([blob], name);
        }
      } 
    },

// 大文件本地路径转换成File文件流
// 文件基础信息（大文件，超过2G）
const file = {
    size:  xxxx,
    localPath: 'c://xxxxx.test.txt',
}

// 大文件要通过分片读取
const chunkSize = 1024 * 1204 * 60 // 每片大小为 60M
// 计算块的数量
const numberOfChunks = Math.ceil(file.size/ chunkSize )
let start = 0
for (let i = 1; i <= numberOfChunks; i++) {
        // 解决fs.createReadStream读取分段文件，总是会大1的问题
        const end = Math.min(i * chunkSize, file.size) - 1
        const readStream = fs.createReadStream(file.localPath, {
           start,
           end,
           highWaterMark: this.chunkSize,
         })
        const chunkBuffer = []
  
         readStream.on('data', (chunk) => {
            chunkBuffer.push(chunk)
         })
        // 读取结束
         readStream.on('end', (chunk) => {
            const blob = new Blob(chunkBuffer)
            const _chunkFile = new File([blob], item.name)
            // 解决fs.createReadStream读取分段文件，总是会大1的问题
            start = end + 1
         })

   }