How can I keep a multipart form upload in memory (skip the file)?

[jcalfee]

I need to parse many requests with images and forward them to another server. Is there a way to avoid writing each one to a file? I would rather access some sort of Buffer with the file's data in it. Here is an example request:

curl -F "image=@$HOME/Pictures/blue_red_pill.jpg" -F "username=slim" http://localhost:3234/upload

Here is what I have so far:

const form = new formidable.IncomingForm()
const koaBody = require('koa-better-body')({
    multipart: true,
    IncomingForm: form,
})

form.onPart = function(part) {
    if (!part.filename) {
        // let formidable handle all non-file parts
        form.handlePart(part)
        return
    }   

    part.on('data', buffer => {
        if (buffer.length == 0) return
        console.log('received', buffer.length, 'bytes');
        // form.handlePart(???
    })

    part.on('end', () => {
        console.log('end');
        // form.handlePart(???
    })
    // part.on('error' // what about cleanup on error?
}

const router = require('koa-router')()
router.post('/upload', koaBody, function *() {
    const buffer = this.request[???]
})

I'm receiving the data, but I don't have anywhere to store it. Is there a way to get the data I collected back into the request?

[tunnckoCore]

I don't know, I'm open for some ideas. I think it's more formidable thing. More and more formidable related issues comes here. It is a bit outdated for me and I'm not sure it is so fast as it says, what you think?

[tunnckoCore]

Actually we can add data listener and pass the buffer to the done() where we currently pass fields and files here, it's not a problem, but I'm not sure if it will help. I think it will create file in /tmp anyway and you can't stop this cuz this is how formidable works internally (didn't look it soon so I cant remember)?

We need stable, fast and good multipart parser for years.

Formidable always writes files to disk this.uploadDir = opts.uploadDir || (os.tmpdir && os.tmpdir()) || os.tmpDir();

koa-multer, bases on multer, has a memory strategy. For big files, it's maybe less secure (v8 still has a hard memory limit which could be exceeded by uploading a large file), but for typical use cases it's faster and doesn't rely on any local file system permission or local folder structure.