FS.writeFile is writing incorrect data when passed a string containing binary data.

[98ahni]

I have a string with the contents of a binary file, but when I write this string to a file using FS.writeFile("/WorkDir/" + file.name, res.body); the file gets corrupted for some reason. The file should be 7,203,723 bytes long, instead it becomes 10,480,395 bytes once saved. The extra bytes are seemingly inserted randomly through the file making it unreadable.

[sbc100]

I think this is because writeFile is doing to first UTF8 encode the string and then write the result, which is not what you want for a binary file.

Assuming res is the result of a fetch request I imagine you probably await the res.arrayBuffer() and pass that to FS.writeFile.

[98ahni]

The response res is a json object, which doesn't have the arrayBuffer() function. If I run JSON.stringify(res); I get:

{
    "result":false,
    "body":"ID3\u0004\u0000\u0000\u0000\u0000\u0001;TXXX[...]",
    "headers":{
        "cache-control":"private, max-age=0, must-revalidate",
        "content-encoding":"gzip",
        "content-type":"text/plain;charset=UTF-8",
        "date":"Wed, 05 Jun 2024 07:50:29 GMT",
        "expires":"Wed, 05 Jun 2024 07:50:29 GMT",
        "server":"ESF",
        "vary":"Origin, X-Origin",
        "x-guploader-uploadid":"[...]",
        "Content-Type":"audio/mpeg"
    },
    "status":200,
    "statusText":null
}

The exact same code works for a *.txt file and it has the same response as above, just a different "body" and "Content-Type". The response even says that it uses UTF-8.

[sbc100]

What does Object.keys(res) show? Are you sure it doesn't have an arrayBuffer() method? Where does res come from? It kind of looks like the result of fetch?

In any case, what you need here is an ArrayBuffer representing the binary, no the JS string form.

[98ahni]

Object.keys(res) returns (5) ['result', 'body', 'headers', 'status', 'statusText'].

The response comes from:

const res = await gapi.client.drive.files.get({
    'fileId': file.id,
    'alt': 'media'
});

It always comes as a string.

[sbc100]

You should be able to convert that string to an ArrayBuffer and then pass that to FS.writeFile

[98ahni]

How do I do that?

[98ahni]

This seems to be one of many oversights from Google and the documentation they provide. The "body" is a File blob according to the docs. It does not specify how to choose whether it's represented as a string or an ArrayBuffer, just that you can. Apparently, this is set in the Google.drive() constructor which doesn't exist in the JS version of the api. The discussions I could find for fixing this ended with one dev team blaming another.
Sorry for the mini rant, on to my "solution".

I managed to brute-force it by looping over the string, getting each char and then passing that to a Uint8Array.

const res = await gapi.client.drive.files.get({
    'fileId': file.id,
    'alt': 'media'
});
var bytes = [];
for (var i = 0; i < res.body.length; ++i) {
    bytes.push(res.body.charCodeAt(i));
}
FS.writeFile("/GoogleDrive/" + file.name, new Uint8Array(bytes));

Which works, but it feels like the wrong solution. I'm open to suggestions on a better way.

[sbc100]

That looks like the correct solution to me.