通过Node从GridFS读取时如何解码base64文件? [英] How do decode base64 file when reading from GridFS via Node?

问题描述

我正在尝试使用Node从MongoDB GridFS集合中读取以base64编码的文件.我已经能够将文件从MongoDB保存到我的本地计算机上，但是它是base64格式的，我想以未编码的方式保存它.

I'm trying to read a file encoded in base64 from a MongoDB GridFS collection using Node. I have been able to get the file saved from MongoDB to my local machine, but it's in base64 format and I want to save it unencoded.

理想情况下，我想即时"解码文件而不必保存一次，然后读取>解码>将其写回到文件系统中.

Ideally I would like to decode the file "on-the-fly" without having to save once, to then read > decode > write it back to the filesystem.

我的代码当前看起来像这样...

My code currently looks like this...

return new Promise(async (resolve, reject) => {
    let bucket = new mongodb.GridFSBucket(db, {bucketName: 'Binaries'});
    let objectID = new mongodb.ObjectID(fileID);

    // create the download stream
    bucket.openDownloadStream(objectID)
        .once('error', async (error) => {
            reject(error);
        })
        .once('end', async () => {
            resolve(downloadPath);
        })
        // pipe the file to the stream
        .pipe(fs.createWriteStream(downloadPath));
});

有什么想法吗?

推荐答案

以防万一其他人在看这个东西，这就是我降落的地方...

Just in case anyone else is looking at this, here's where I landed...

   return new Promise(async (resolve, reject) => {
        let bucket = new mongodb.GridFSBucket(db, {
            bucketName: 'Binaries'
        });
        let objectID = new mongodb.ObjectID(fileInformation._id);

        // temporary variable to hold image
        var data = [];

        // create the download stream
        let downloadStream = bucket.openDownloadStream(objectID);
        downloadStream.on('data', (chunk) => {
            data.push(chunk);
        });
        downloadStream.on('error', async (error) => {
            reject(error);
        });
        downloadStream.on('end', async () => {
            // convert from base64 and write to file system
            let bufferBase64 = Buffer.concat(data)
            let bufferDecoded = Buffer.from(bufferBase64.toString(), 'base64');
            fs.writeFileSync(fileName, bufferDecoded, 'binary');
            resolve(fileName);
        });
    });

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