How long does a Blob file created in Google Chrome Exist?

Question

Part of a Google Chrome Extension I am working on has this existing JavaScript below for creating a Blog file from a screenshot image...

    getBlob = function(canvas) {
        // standard dataURI can be too big, let's blob instead
        // http://code.google.com/p/chromium/issues/detail?id=69227#c27

        var dataURI = canvas.toDataURL(),
            // convert base64 to raw binary data held in a string
            // doesn't handle URLEncoded DataURIs
            byteString = atob(dataURI.split(',')[1]),
            // separate out the mime component
            mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0],
            // write the bytes of the string to an ArrayBuffer
            ab = new ArrayBuffer(byteString.length),
            ia = new Uint8Array(ab),
            i;

        for (i = 0; i < byteString.length; i++) {
            ia[i] = byteString.charCodeAt(i);
        }

        return new Blob([ab], {type: mimeString});
    },

    saveBlob = function(blob, filename, callback, errback) {
        var onWriteEnd = function() {
            // Return the name of the file that now contains the blob.
            callback('filesystem:chrome-extension://' + chrome.runtime.id + '/temporary/' + filename);
        };

        window.webkitRequestFileSystem(TEMPORARY, 1024*1024, function(fs){
            fs.root.getFile(filename, {create:true}, function(fileEntry) {
                fileEntry.createWriter(function(fileWriter) {
                    fileWriter.onwriteend = onWriteEnd;
                    fileWriter.write(blob);
                }, errback);
            }, errback);
        }, errback);
    },

Looking at saveBlob(blob, filename, callback, errback) above. How long would a file created this way exist? Does it disappear when the browser is closed?

guest271314 · Answer 1 · 2016-05-02T14:29:28.967

2

The file would exist until directly deleted by user or Clear browsing data is used at settings; though there is no guarantee of persistence.

4.4.1.2 Constants

TEMPORARY of type unsigned short Used for storage with no guarantee of persistence.

See also Temporary storage

edited May 02 '16 at 14:29

answered May 02 '16 at 05:47

guest271314

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I actually just came across this `Data stored using TEMPORARY can be removed at the browser's discretion (for example if more space is needed).` and I see it called here `window.webkitRequestFileSystem(TEMPORARY, 1024*1024,)` – JasonDavis May 02 '16 at 05:48
Yes. That is another way a file could be removed from filesystem. You can check if file exists in `FileSystem` using `DevTools` -> `Experiments` -> check `FileSystem inspection` , see http://stackoverflow.com/questions/36098129/how-to-write-in-file-user-directory-using-javascript/ – guest271314 May 02 '16 at 05:49
@JasonDavis Try visiting plnkr http://plnkr.co/edit/EVVNYYUvHiM545T06kMC?p=preview , closing chrome, re-launching chrome then at `terminal` `$ ~/.config/chrome/Default/File\ System` , then `$ ls` . The numerical directories listed should contain the files saved to `FileSystem` – guest271314 May 02 '16 at 06:04
@JasonDavis Clearing browsing data also delete file in `FileSystem` – guest271314 May 02 '16 at 13:43
@ZigMandel In the original form, when I downvoted, it was incorrect and very short without any references. – Xan May 02 '16 at 14:45

How long does a Blob file created in Google Chrome Exist?

1 Answers1