Read from Dropbox stream into Buffer - node.js

Question

I need to download a file from Dropbox into buffer on my server. Due to a security issues I can't download a file directly to a client. Therefore I send request to my server, then fetch the file from Dropbox and then forward it to the client. I managed to implement this writing Dropbox stream to a file on my server and then sending it to a client.
I need to implement this mechanism without writing Dropbox stream into file on my server. I need to create a buffer and write into it and then forward the buffer to a client.
export const downloadFileFromDropbox = async function downloadFileFromDropbox(fileName,
folderNameOnDropbox) {
let isSucceeded;
const message = [];
let downloadResult;
let fileBuffered = "";
// authentication
const dropbox = dropboxV2Api.authenticate({
token: process.env.DEV_DROPBOX_SECRET_KEY
});
// configuring parameters
const params = Object.freeze({
resource: "files/download",
parameters: {
path: `/${folderNameOnDropbox}/${fileName}`
}
});
let dropboxPromise = new Promise(function (resolve, reject) {
dropbox(params, function (err, result) {
if (err) {
reject(err);
} else {
resolve(result);
}
}).pipe(fs.createWriteStream(/* need to implement buffer here */));
});
await dropboxPromise.then(async function (resultObj) {
isSucceeded = true;
message.push("fileDownload_OK");
}).catch(async function (err) {
isSucceeded = false;
message.push(err.message);
});
downloadResult = {
isSucceeded,
message,
/* Buffer */
};
return downloadResult;
};

Answer 1

There is no way to convert a file into buffer without writing it in some location
What worked for me is:
write the file in a temporary folder
Read it and convert into buffer
send the buffer back to the client
delete the file from the temporary location
here's my code :
dropbox = dropboxV2Api.authenticate({ token: credentials.access_token });
dropbox(
{
resource: 'files/download',
parameters: {
path: `${req.query.folder}` + `/${req.query.filename}`,
},
},
(err, result, response) => {
//download completed
if (err) {
return res.status(500).send(err);
} else {
console.log('download completed');
}
}
).pipe(
fs
.createWriteStream(`./app/tmp/` + `${req.query.filename}`)
.on('finish', () => {
fs.readFile(
`./app/tmp/` + `${req.query.filename}`,
function (err, buffer) {
if (err) {
res.status(500).send(err);
} else {
fs.unlink(`./app/tmp/` + `${req.query.filename}`, (err) => {
if (err) {
console.error(err);
return;
}
//file removed
res.status(200).send(buffer);
});
}
}
);
})
);
I hope this will help you even though it's a little bit late