Converting file into Base64String and back again

Question

The title says it all:

1. I read in a tar.gz archive like so
2. break the file into an array of bytes
3. Convert those bytes into a Base64 string
4. Convert that Base64 string back into an array of bytes
5. 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);
}

Thanks!

Inrush

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. – Gaitan

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 – Inrush

Answer 1

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);

Choler

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 – Dynah

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

@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 – Choler

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

Answer 2

Another working example in VB.NET:

Public Function base64Encode(ByVal myDataToEncode As String) As String
    Try
        Dim myEncodeData_byte As Byte() = New Byte(myDataToEncode.Length - 1) {}
        myEncodeData_byte = System.Text.Encoding.UTF8.GetBytes(myDataToEncode)
        Dim myEncodedData As String = Convert.ToBase64String(myEncodeData_byte)
        Return myEncodedData
    Catch ex As Exception
        Throw (New Exception("Error in base64Encode" & ex.Message))
    End Try
    '
End Function

Apivorous

Answer 3

private String encodeFileToBase64Binary(File file){    
String encodedfile = null;  
try {  
    FileInputStream fileInputStreamReader = new FileInputStream(file);  
    byte[] bytes = new byte[(int)file.length()];
    fileInputStreamReader.read(bytes);  
    encodedfile = Base64.encodeBase64(bytes).toString();  
} catch (FileNotFoundException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
} catch (IOException e) {  
    // TODO Auto-generated catch block  
    e.printStackTrace();  
}  
    return encodedfile;  
}

Pagano

While this code may answer the question, providing additional context regarding how and/or why it solves the problem would improve the answer's long-term value. Please read this how-to-answer for providing quality answer. – Lucinalucinda

why, again, do we need java if OP uses c#? – Choler

@Choler why, again, do we need java ? – Neckpiece

Answer 4

For Java, consider using Apache Commons FileUtils:

/**
 * Convert a file to base64 string representation
 */
public String fileToBase64(File file) throws IOException {
    final byte[] bytes = FileUtils.readFileToByteArray(file);
    return Base64.getEncoder().encodeToString(bytes);
}

/**
 * Convert base64 string representation to a file
 */
public void base64ToFile(String base64String, String filePath) throws IOException {
    byte[] bytes = Base64.getDecoder().decode(base64String);
    FileUtils.writeByteArrayToFile(new File(filePath), bytes);
}

Burseraceous

The question is tagged under C#, its better if you provide the solution for C#. – Muna