Converting file into Base64String and back again

Question

The title says it all:

I read in a tar.gz archive like so
break the file into an array of bytes
Convert those bytes into a Base64 string
Convert that Base64 string back into an array of bytes
Write those bytes back into a new tar.gz file

I can confirm that both files are the same size (the below method returns true), but I can no longer extract the copy version.

Am I missing something?

Boolean MyMethod(){
    using (StreamReader sr = new StreamReader("C:\...\file.tar.gz")) {
        String AsString = sr.ReadToEnd();
        byte[] AsBytes = new byte[AsString.Length];
        Buffer.BlockCopy(AsString.ToCharArray(), 0, AsBytes, 0, AsBytes.Length);
        String AsBase64String = Convert.ToBase64String(AsBytes);

        byte[] tempBytes = Convert.FromBase64String(AsBase64String);
        File.WriteAllBytes(@"C:\...\file_copy.tar.gz", tempBytes);
    }
    FileInfo orig = new FileInfo("C:\...\file.tar.gz");
    FileInfo copy = new FileInfo("C:\...\file_copy.tar.gz");
    // Confirm that both original and copy file have the same number of bytes
    return (orig.Length) == (copy.Length);
}

EDIT: The working example is much simpler (Thanks to @T.S.):

Boolean MyMethod(){
    byte[] AsBytes = File.ReadAllBytes(@"C:\...\file.tar.gz");
    String AsBase64String = Convert.ToBase64String(AsBytes);

    byte[] tempBytes = Convert.FromBase64String(AsBase64String);
    File.WriteAllBytes(@"C:\...\file_copy.tar.gz", tempBytes);

    FileInfo orig = new FileInfo(@"C:\...\file.tar.gz");
    FileInfo copy = new FileInfo(@"C:\...\file_copy.tar.gz");
    // Confirm that both original and copy file have the same number of bytes
    return (orig.Length) == (copy.Length);
}

You can't just change the the content of a compressed file like that. You'll have to decompress the file in step 1 instead of just read it in directly as is. And then step 5 will likewise have to be recompressing the data instead of just writing out the bytes directly. — itsme86
– itsme86, Commented Sep 18, 2014 at 18:10
Fortunately, as there was no actual manipulation of the file itself (basically just moving it from point A to B) this particular task doesn't require any (de/)compression — darkpbj
– darkpbj, Commented Sep 18, 2014 at 18:29

T.S. · Accepted Answer · 2014-09-18 18:16:52Z

440

If you want for some reason to convert your file to base-64 string. Like if you want to pass it via internet, etc... you can do this

Byte[] bytes = File.ReadAllBytes("path");
String file = Convert.ToBase64String(bytes);

And correspondingly, read back to file:

Byte[] bytes = Convert.FromBase64String(b64Str);
File.WriteAllBytes(path, bytes);

answered Sep 18, 2014 at 18:16

T.S.

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4 Comments

Mister SirCode Over a year ago

Thankyou for the information, I tried going along with the answer below, but it didnt help, but this seemed to solve my problem with a simple openFileDialog

Olorunfemi Davis Over a year ago

What if ToBase64String returns System.OutOfMemoryException? How do you optimize for large files and limited memory

T.S. Over a year ago

@OlorunfemiAjibulu then I suspect, you would need to use streams. Or break string into parts. One time I wrote custom encryption for large files where we saved encrypted chunks. We added 4 bytes to save integer value for chunk size. This way we knew to read so many positions

Olorunfemi Davis Over a year ago

Interesting @TaylorSpark. I used streams and I was fine.

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