Base64 directly to file

  • Thread starter Thread starter sead.alispahic
  • Start date Start date
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sead.alispahic

I am getting a huge file attachment from SWA web service, obviously in
Base64. Is there a way to decode the Base64 string directly to a file
(FileStream or similar) instead to byte array?
 
I am getting a huge file attachment from SWA web service, obviously in
Base64. Is there a way to decode the Base64 string directly to a file
(FileStream or similar) instead to byte array?
Click to expand...

Use CryptoStream with FromBase64Transform. There's an example in the
FromBase64Transform description in MSDN which does pretty much what you
need.
 
Hi,
I dont know about the directly decoding it to file, but you could read fixed
chunks in sizes which should be multiple of 4 (in a loop) and convert and
write them to the destination file (i have used the chunk size of 4):

something like the following code (its just using a textbox but u can use
filestream of course);

string base64text = textBox2.Text;
int startingindex = 0;
txttranslated.Clear(); // destination textbox
while (startingindex<base64text.Length)
{
string tmp = base64text.Substring(startingindex, 4);
startingindex += 4;
txttranslated.AppendText (Encoding.ASCII.GetString (
Convert.FromBase64String(tmp)));
}

hope that help ..
Regards,

...ab
 
Hi,

If you've got the byte[] from the base64 string then you
can just write it to the file e.g. by FileStream.

private static void Base64ToFile(string base64String, string dstFilePath) {
byte[] dataBuffer=Convert.FromBase64String(base64String);
using( FileStream fileStream=new FileStream(dstFilePath
, FileMode.Create
, FileAccess.Write) ) {
if( dataBuffer.Length>0 ) {
fileStream.Write(dataBuffer, 0, dataBuffer.Length);
}
}
}

HTH
Marcin

(e-mail address removed) napisa³(a):
 
Marcin said:
If you've got the byte[] from the base64 string then you
can just write it to the file e.g. by FileStream.
Click to expand...

I believe the OP's point is that they don't want to have another full
copy of the data in memory at the same time - and indeed they may not
even have a *single* copy of the data in memory, if they stream the
input. Doing everything in one shot could be very expensive in terms of
memory.

Jon
 
Hi Jon,

Jon Skeet [C# MVP] napisa³(a):
Marcin said:
If you've got the byte[] from the base64 string then you
can just write it to the file e.g. by FileStream.
Click to expand...

I believe the OP's point is that they don't want to have another full
copy of the data in memory at the same time - and indeed they may not
even have a *single* copy of the data in memory, if they stream the
input. Doing everything in one shot could be very expensive in terms of
memory.

Jon
Click to expand...

You're right!
I missed the "huge file attachment" as an input.

Marcin
 
Thx you all for the responses

I have decided to go with Abubakar's suggestions and, for the future
reference, this is a simple function that does what I need
//--------------------------------------------------------------------------------
private string Base64Decode(string data, string fileName)
{
FileStream fs = new FileStream(fileName, FileMode.OpenOrCreate,
FileAccess.Write);
int sizeOfChunk = 4;
int startPosition = 0;
while (startPosition < data.Length)
{
string tmp = data.Substring(startPosition, sizeOfChunk);
startPosition = startPosition + sizeOfChunk;
byte[] tmpArr = Convert.FromBase64String(tmp);
fs.Write(tmpArr, 0, tmpArr.Length);
}
fs.Close();
fs.Dispose();
return fileName;
}
//--------------------------------------------------------------------------------
 
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