如何从缓冲区中提取文件内容？

Question

我正在探索 Node.js，在创建使用 multer 模块将小文件上传到内存的功能时遇到了一个问题。

我正在使用 multer 的内置 MemoryStorage 选项。文件上传成功，文件元数据可以在 ExpressJS 的 req 对象中访问。

现在我希望能够从缓冲区中读取文件内容，因为该文件将采用 .csv 格式，稍后将转换为 JSON。我需要文件的字符串内容来执行转换。

这是我的路由器处理程序：

const memStorage = multer.memoryStorage();
const memUpload = multer({
  storage: memStorage,
  limits: { fileSize: 30 * 1024 * 2014, files: 1 }
});
router.post(
  '/tables/csv',
  memUpload.single('file'),
  (req, res) => {
    const file = req.file;
    let buffer = fs.readFileSync(file.buffer);
    console.log(buffer);
  }
);

.csv 文件使用：

Risk Category,Risk ID,Risk Value
Some,Some,Some
Some,Some,Some
Some,Some,Some

控制台输出：

Error: ENOENT: no such file or directory, open 'Risk Category,Risk ID,Risk Value
Some,Some,Some
Some,Some,Some
Some,Some,Some'
    at Object.openSync (fs.js:436:3)
    at Object.readFileSync (fs.js:341:35)
    at router.post (C:\client_projects\tt\sarcs-hotline\router\index.js:1039:21)
    at Layer.handle [as handle_request] (C:\client_projects\tt\sarcs-hotline\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\client_projects\tt\sarcs-hotline\node_modules\express\lib\router\route.js:137:13)
    at Array.<anonymous> (C:\client_projects\tt\sarcs-hotline\node_modules\multer\lib\make-middleware.js:53:37)
    at listener (C:\client_projects\tt\sarcs-hotline\node_modules\on-finished\index.js:169:15)
    at onFinish (C:\client_projects\tt\sarcs-hotline\node_modules\on-finished\index.js:100:5)
    at callback (C:\client_projects\tt\sarcs-hotline\node_modules\ee-first\index.js:55:10)
    at IncomingMessage.onevent (C:\client_projects\tt\sarcs-hotline\node_modules\ee-first\index.js:93:5)
    at IncomingMessage.emit (events.js:182:13)
    at endReadableNT (_stream_readable.js:1094:12)
    at process._tickCallback (internal/process/next_tick.js:63:19)

Answer 1

您可以在调用 fs.readFileSync 获取字符串时指定您的编码：

fs.readFileSync(file.buffer, { encoding: 'utf8' });

或者您不需要 readFileSync。你可以像

一样调用buffer.toString(encoding)

file.buffer.toString('utf8');

如何从缓冲区中提取文件内容？

How to extract file contents from a Buffer?

javascript

fs

node.js

multer