在nodejs中的createReadStream中追加数据

Question

我有一个 node.js 应用程序，我在电子缓冲区中发布视频数据。

app.post("/add/", (req, res) => {
    var user_file = req.body.user_file;
    
    // this initializes a writestream where I can write my buffers and then save this file name in the database

    storage_stream = require("fs").createWriteStream(user_file+'.webm');

// db logic here...

    res.end(JSON.stringify({'success':'added'}))
})

上面的函数按预期运行，现在我想以 10 秒的间隔在另一个函数上发布我的缓冲区

app.post("/post_buffer/", (req, res) => {
    const user_file = req.body.user_file
    const buffer = Buffer.from(req.body.video_buffer);
      
//    I want to read the existing stream of the user and append the buffers in that stream, something like this

//  if I do something like this
//  const stored_stream = require("fs").createWriteStream(user_file+'.webm');

//  this overwrites the existing file.

    const stored_stream = require("fs").createReadStream(user_file+'.webm');
    stored_stream.write(buffer);     // this throws error, read stream don't have .write() function
    
//  OR
//  stored_stream.push(buffer);      // this doesn't throw any error but makes the file corrupted

    res.end(JSON.stringify({'success':true}))

})

是否有任何解决方法？如何将缓冲区附加到现有流中？ 任何帮助将不胜感激。

Answer 1

该文件必须以附加模式从 app.post("/post_buffer/") 打开。如果文件不存在，则使用追加模式将创建该文件，并且在任何情况下都会将数据追加到文件末尾。

官方文档中记录了不同的操作系统文件处理程序标志： file-system-flags

app.post("/post_buffer/", (req, res) => {
    ...
    // Open file handle to append incoming buffer.
    const fileHandle = await fs.promises.open(user_file+'.webm', 'a'); // 'a' -> append mode
    // Initialize a write stream from file handle.
    const stored_stream = fileHandle.createWriteStream();
    // Write the incoming buffer to the write stream and 
    // await the buffer to be flushed.
    await new Promise(resolve => stored_stream.end(buffer, resolve));
   
    ...
})