Base64: Public Domain Base64 Encoder/Decoder

Something Sun Should Have Included Long Ago

(And now has! As of Java v1.8, there is a Base64 class. Finally.)

This is a Public Domain Java class providing very fast Base64 encoding and decoding in the form of convenience methods and input/output streams.

There are other Base64 utilities on the Internet, some part of proprietary packages, some with various open source licenses. In any event, I hope with one or more of these Base64 tools, you won't have to write your own like I did.

If you use Maven, thank Owen O'Malley from Apache and Matthew from Sensible Development for working up a Base64 Maven Repository.

Thanks to Brian Burton for providing this Base64Test.java test class for use with JUnit.org. (The test file hasn't been updated in a while.)

You may view the Base64 javadoc API online, if you like.

Version 2.3 is not a drop-in replacement to earlier versions. I finally improved the error handling such that the code will throw exceptions when there is a problem instead of just quietly returning null. Sorry if you like the old style (I did too for a long time), but I changed it and think it's better form this way. There are also some helper methods for encoding data without creating a String object; that should help with very large amounts of data or when memory is tight.

Examples

The easiest way to convert some data is with the convenience methods:

String result1 = Base64.encodeObject( mySerializableObject );
String result2 = Base64.encodeBytes( new byte[]{ 3, 34, 116, 9 } );

Or you can use the very efficient streams:

OutputStream out = new Base64.OutputStream( 
                    new FileOutputStream( "out.txt" ) );
// Go on about your outputting...
// ...

InputStream in = new Base64.InputStream( 
                  new FileInputStream( "in.txt" ) );
// Go on about your inputting...
// ...

There are defaults (OutputStream encodes, InputStream decodes), but you can easily override that:

OutputStream out = new Base64.OutputStream( 
                    new FileOutputStream( "out.txt" ), Base64.DECODE );
// Go on about your outputting...
// ...

A Note About Public Domain

I have released this software into the Public Domain. That means you can do whatever you want with it. Really. You don't have to match it up with any other open source license &em; just use it. You can rename the files, move the Java packages, whatever you want. If your lawyers say you have to have a license, contact me, and I'll make a special release to you under whatever reasonable license you desire: MIT, BSD, GPL, whatever.

Alternatives

There are alternative Base64 classes out there. For various reasons you might prefer them. It's OK; you won't hurt my feelings. Keep in mind particularly that there are a lot of "helper functions" in the Base64.java class available on this page, and if you're doing embedded work, you'll either want to strip out the fluff or just grab a more minimal implementation. Here are some that I've found:

Changes

v2.3.7 - Fixed subtle bug when base 64 input stream contained the value 01111111, which is an invalid base 64 character but should not throw an ArrayIndexOutOfBoundsException either. Led to discovery of mishandling (or potential for better handling) of other bad input characters. You should now get an IOException if you try decoding something that has bad characters in it.
v2.3.6 - Fixed bug when breaking lines and the final byte of the encoded string ended in the last column; the buffer was not properly shrunk and contained an extra (null) byte that made it into the string.
v2.3.4 - Fixed bug when working with gzipped streams whereby flushing the Base64.OutputStream closed the Base64 encoding (by padding with equals signs) too soon. Also added an option to suppress the automatic decoding of gzipped streams.
v2.3.3 - Changed default char encoding to US-ASCII which reduces the internal Java footprint with its CharEncoders and so forth. Fixed some javadocs that were inconsistent. Removed imports and specified things like java.io.IOException explicitly inline.
v2.3.2 - Reduced memory footprint! Finally refined the "guessing" of how big the final encoded data will be so that the code doesn't have to create two output arrays: an oversized initial one and then a final, exact-sized one. Big win when using the encodeBytesToBytes(byte[]) family of methods (and not using the gzip options which uses a different mechanism with streams and stuff).
v2.3.1 - Added encodeBytesToBytes(byte[], int, int, int) and some similar helper methods to be more efficient with memory by not returning a String but just a byte array.
v2.3 - This is not a drop-in replacement! This is two years of comments and bug fixes queued up and finally executed. Thanks to everyone who sent me stuff, and I'm sorry I wasn't able to distribute your fixes to everyone else. Much bad coding was cleaned up including throwing exceptions where necessary instead of returning null values or something similar. Here are some changes that may affect you:
- Does not break lines, by default. This is to keep in compliance with RFC3548.
- Throws exceptions instead of returning null values. Because some operations (especially those that may permit the GZIP option) use IO streams, there is a possiblity of an java.io.IOException being thrown. After some discussion and thought, I've changed the behavior of the methods to throw java.io.IOExceptions rather than return null if ever there's an error. I think this is more appropriate, though it will require some changes to your code. Sorry, it should have been done this way to begin with.
- Removed all references to System.out, System.err, and the like. Shame on me. All I can say is sorry they were ever there.
- Throws NullPointerExceptions and IllegalArgumentExceptions as needed such as when passed arrays are null or offsets are invalid.
- Cleaned up as much javadoc as I could to avoid any javadoc warnings. This was especially annoying before for people who were thorough in their own projects and then had gobs of javadoc warnings on this file.
v2.2.2 - Fixed encodeFileToFile and decodeFileToFile to use the Base64.InputStream class to encode and decode on the fly which uses less memory than encoding/decoding an entire file into memory before writing.
v2.2.1 - Fixed bug using URL_SAFE and ORDERED encodings. Fixed bug when using very small files (~< 40 bytes).
v2.2 - Added some helper methods for encoding/decoding directly from one file to the next. Also added a main() method to support command line encoding/decoding from one file to the next. Also added these Base64 dialects:
1. The default is RFC3548 format.
2. Calling Base64.setFormat(Base64.BASE64_FORMAT.URLSAFE_FORMAT) generates URL and file name friendly format as described in Section 4 of RFC3548. http://www.faqs.org/rfcs/rfc3548.html
3. Calling Base64.setFormat(Base64.BASE64_FORMAT.ORDERED_FORMAT) generates URL and file name friendly format that preserves lexical ordering as described in http://www.faqs.org/qa/rfcc-1940.html
Special thanks to Jim Kellerman at http://www.powerset.com/ for contributing the new Base64 dialects.
v2.1 - Cleaned up javadoc comments and unused variables and methods. Added some convenience methods for reading and writing to and from files.
v2.0.2 - Now specifies UTF-8 encoding in places where the code fails on systems with other encodings (like EBCDIC).
v2.0.1 - Fixed an error when decoding a single byte, that is, when the encoded data was a single byte.
v2.0 - I got rid of methods that used booleans to set options. Now everything is more consolidated and cleaner. The code now detects when data that's being decoded is gzip-compressed and will decompress it automatically. Generally things are cleaner. You'll probably have to change some method calls that you were making to support the new options format (ints that you "OR" together).
v1.5.1 - Fixed bug when decompressing and decoding to a byte[] using decode( String s, boolean gzipCompressed ). Added the ability to "suspend" encoding in the Output Stream so you can turn on and off the encoding if you need to embed base64 data in an otherwise "normal" stream (like an XML file). This has not been fully tested, so please alert me to bugs.
v1.5 - Output stream pases on flush() command but doesn't do anything itself. This helps when using GZIP streams. Added the ability to GZip-compress objects before encoding them.
v1.4 - Added some helper methods for reading and writing to/from files.
v1.3.6 - Fixed OutputStream.flush() so that 'position' is reset.
v1.3.5 - Added flag to turn on and off line breaks. Fixed bug in input stream where last buffer being read, if not completely full, was not returned.
v1.3.4 - Fixed when Improperly padded base64 stream exception was incorrectly thrown.
A bug has been fixed that kept I/O streams from working at all, really.
A bug has been fixed affecting you if you use the Base64.InputStream to encode data.
A bug has been fixed where if you specified an offset when encoding an array of bytes, the offset was ignored.