Hi Jeff,
I agree with Paul's comment on your posting.
The encoded base64 data must be of length divisible by 4. It's the proper
action for the encoder to append pad characters ('=') at the end, and you
shouldn't try to remove them.
And when you decode the data, you should also pass in the whole data
including pads.
Cheers,
Sandy Gao
Software Developer, IBM Canada
(1-416) 448-3255
[EMAIL PROTECTED]
"Jeff Rafter"
<[EMAIL PROTECTED] To: <[EMAIL PROTECTED]>
hlink.net> cc:
Subject: Base64 encoding
question
04/26/2001 04:52
AM
Please respond
to xerces-j-user
I have tried searching for the answer to this question but have not been
able to find the answer: In xerces-j the Base64 encoding scheme appends
"pad" bytes at the end of every call to "encode". However when decoding
the
"pad" bytes are not considered. To get around this I have written my code
as follows:
// Write the binary info
StringBuffer sBuf = new StringBuffer();
// Declare an encoder
Base64 encoder = new Base64();
// Declare a buffer
byte[] buf = new byte[fileIn.available()];
// read each chunk
bufferedFileIn.read(buf);
// add the text to the StringBuffer (this is ugly!)
sBuf.append(new String(encoder.encode(buf)));
// Clip the pad bytes...
sBuf.setLength(sBuf.length()-2);
// Now that we have a string buffer let's set the element content
root.appendChild(doc.createTextNode("" + sBuf));
This code works-- but when encoding a large data file, such as an image,
the
entire file must be read into memory. I at first attempted to read and
write in small chunks (64 bytes) but couldn't resolve the pad bytes well
without consistently clipping and recreating new strings. I admit I am not
great at this and don't have a lot of history with Base64 encoding, so I am
wondering if anyone has a more elegant solution. On the flip side my
decoding method also has problems as it takes the entire encoded element
content and attempts the reverse without breaking it into chunks:
// Get the Content (uh... do this better)
Node content = root.getFirstChild();
// Declare an encoder
Base64 encoder = new Base64();
// Declare a buffer
byte[] buf = content.getNodeValue().getBytes();
// Write the decoded value
bufferedFileOut.write(encoder.decode(buf));
bufferedFileOut.flush();
So I essentially have the same problem going in the reverse order. I know
I
should probably be using SAX to stream the content as well-- and that the
DOM is holding the whole text node in memory anyway, this just demostrates
what is going on with the base64 encoding. I am also not seeking to find
out whether or not placing an encoded image into an XML file is good
practice-- that answer has been well documented elsewhere.
Thanks in advance,
Jeff Rafter
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