Class Base64

java.lang.Object
org.java_websocket.util.Base64

public class Base64 extends Object

Encodes and decodes to and from Base64 notation.

Homepage: http://iharder.net/base64.

Example:

String encoded = Base64.encode( myByteArray );
byte[] myByteArray = Base64.decode( encoded );

The options parameter, which appears in a few places, is used to pass several pieces of information to the encoder. In the "higher level" methods such as encodeBytes( bytes, options ) the options parameter can be used to indicate such things as first gzipping the bytes before encoding them, not inserting linefeeds, and encoding using the URL-safe and Ordered dialects.

Note, according to RFC3548, Section 2.1, implementations should not add line feeds unless explicitly told to do so. I've got Base64 set to this behavior now, although earlier versions broke lines by default.

The constants defined in Base64 can be OR-ed together to combine options, so you might make a call like this:

String encoded = Base64.encodeBytes( mybytes, Base64.GZIP | Base64.DO_BREAK_LINES );

to compress the data before encoding it and then making the output have newline characters.

Also...

String encoded = Base64.encodeBytes( crazyString.getBytes() );

Change Log:

  • 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. Also added experimental support for specifying a class loader when using the method.
  • 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 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 possibility 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 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.
  • v2.2.1 - 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).
  • 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 helper methods to read/write 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 stream" error was thrown at the wrong time.
  • v1.3.3 - Fixed I/O streams which were totally messed up.

I am placing this code in the Public Domain. Do with it as you will. This software comes with no guarantees or warranties but with plenty of well-wishing instead! Please visit http://iharder.net/base64 periodically to check for updates or to contribute improvements.

Version:
2.3.7
  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    A Base64.OutputStream will write data to another java.io.OutputStream, given in the constructor, and encode/decode to/from Base64 notation on the fly.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private static final byte[]
    I don't get the point of this technique, but someone requested it, and it is described here: http://www.faqs.org/qa/rfcc-1940.html.
    private static final byte[]
    Used in decoding the "ordered" dialect of Base64.
    private static final byte[]
    The 64 valid Base64 values.
    private static final byte[]
    Translates a Base64 value to either its 6-bit reconstruction value or a negative number indicating some other meaning.
    private static final byte[]
    Used in the URL- and Filename-safe dialect described in Section 4 of RFC3548: http://www.faqs.org/rfcs/rfc3548.html.
    private static final byte[]
    Used in decoding URL- and Filename-safe dialects of Base64.
    static final int
    Do break lines when encoding.
    static final int
    Specify encoding in first bit.
    private static final byte
    The equals sign (=) as a byte.
    static final int
    Specify that data should be gzip-compressed in second bit.
    private static final int
    Maximum line length (76) of Base64 output.
    private static final byte
    The new line character (\n) as a byte.
    static final int
    No options specified.
    static final int
    Encode using the special "ordered" dialect of Base64 described here: http://www.faqs.org/qa/rfcc-1940.html.
    private static final String
    Preferred encoding.
    static final int
    Encode using Base64-like encoding that is URL- and Filename-safe as described in Section 4 of RFC3548: http://www.faqs.org/rfcs/rfc3548.html.
    private static final byte
     
  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    private
    Defeats instantiation.
  • Method Summary

    Modifier and Type
    Method
    Description
    private static int
    decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset, int options)
    Decodes four bytes from array source and writes the resulting bytes (up to three of them) to destination.
    private static byte[]
    encode3to4(byte[] b4, byte[] threeBytes, int numSigBytes, int options)
    Encodes up to the first three bytes of array threeBytes and returns a four-byte array in Base64 notation.
    private static byte[]
    encode3to4(byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset, int options)
    Encodes up to three bytes of the array source and writes the resulting four Base64 bytes to destination.
    static String
    encodeBytes(byte[] source)
    Encodes a byte array into Base64 notation.
    static String
    encodeBytes(byte[] source, int off, int len, int options)
    Encodes a byte array into Base64 notation.
    static byte[]
    encodeBytesToBytes(byte[] source, int off, int len, int options)
    Similar to encodeBytes(byte[], int, int, int) but returns a byte array instead of instantiating a String.
    private static final byte[]
    getAlphabet(int options)
    Returns one of the _SOMETHING_ALPHABET byte arrays depending on the options specified.
    private static final byte[]
    getDecodabet(int options)
    Returns one of the _SOMETHING_DECODABET byte arrays depending on the options specified.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • NO_OPTIONS

      public static final int NO_OPTIONS
      No options specified. Value is zero.
      See Also:
    • ENCODE

      public static final int ENCODE
      Specify encoding in first bit. Value is one.
      See Also:
    • GZIP

      public static final int GZIP
      Specify that data should be gzip-compressed in second bit. Value is two.
      See Also:
    • DO_BREAK_LINES

      public static final int DO_BREAK_LINES
      Do break lines when encoding. Value is 8.
      See Also:
    • URL_SAFE

      public static final int URL_SAFE
      Encode using Base64-like encoding that is URL- and Filename-safe as described in Section 4 of RFC3548: http://www.faqs.org/rfcs/rfc3548.html. It is important to note that data encoded this way is not officially valid Base64, or at the very least should not be called Base64 without also specifying that is was encoded using the URL- and Filename-safe dialect.
      See Also:
    • ORDERED

      public static final int ORDERED
      Encode using the special "ordered" dialect of Base64 described here: http://www.faqs.org/qa/rfcc-1940.html.
      See Also:
    • MAX_LINE_LENGTH

      private static final int MAX_LINE_LENGTH
      Maximum line length (76) of Base64 output.
      See Also:
    • EQUALS_SIGN

      private static final byte EQUALS_SIGN
      The equals sign (=) as a byte.
      See Also:
    • NEW_LINE

      private static final byte NEW_LINE
      The new line character (\n) as a byte.
      See Also:
    • PREFERRED_ENCODING

      private static final String PREFERRED_ENCODING
      Preferred encoding.
      See Also:
    • WHITE_SPACE_ENC

      private static final byte WHITE_SPACE_ENC
      See Also:
    • _STANDARD_ALPHABET

      private static final byte[] _STANDARD_ALPHABET
      The 64 valid Base64 values.
    • _STANDARD_DECODABET

      private static final byte[] _STANDARD_DECODABET
      Translates a Base64 value to either its 6-bit reconstruction value or a negative number indicating some other meaning.
    • _URL_SAFE_ALPHABET

      private static final byte[] _URL_SAFE_ALPHABET
      Used in the URL- and Filename-safe dialect described in Section 4 of RFC3548: http://www.faqs.org/rfcs/rfc3548.html. Notice that the last two bytes become "hyphen" and "underscore" instead of "plus" and "slash."
    • _URL_SAFE_DECODABET

      private static final byte[] _URL_SAFE_DECODABET
      Used in decoding URL- and Filename-safe dialects of Base64.
    • _ORDERED_ALPHABET

      private static final byte[] _ORDERED_ALPHABET
      I don't get the point of this technique, but someone requested it, and it is described here: http://www.faqs.org/qa/rfcc-1940.html.
    • _ORDERED_DECODABET

      private static final byte[] _ORDERED_DECODABET
      Used in decoding the "ordered" dialect of Base64.
  • Constructor Details

    • Base64

      private Base64()
      Defeats instantiation.
  • Method Details

    • getAlphabet

      private static final byte[] getAlphabet(int options)
      Returns one of the _SOMETHING_ALPHABET byte arrays depending on the options specified. It's possible, though silly, to specify ORDERED and URLSAFE in which case one of them will be picked, though there is no guarantee as to which one will be picked.
    • getDecodabet

      private static final byte[] getDecodabet(int options)
      Returns one of the _SOMETHING_DECODABET byte arrays depending on the options specified. It's possible, though silly, to specify ORDERED and URL_SAFE in which case one of them will be picked, though there is no guarantee as to which one will be picked.
    • encode3to4

      private static byte[] encode3to4(byte[] b4, byte[] threeBytes, int numSigBytes, int options)
      Encodes up to the first three bytes of array threeBytes and returns a four-byte array in Base64 notation. The actual number of significant bytes in your array is given by numSigBytes. The array threeBytes needs only be as big as numSigBytes. Code can reuse a byte array by passing a four-byte array as b4.
      Parameters:
      b4 - A reusable byte array to reduce array instantiation
      threeBytes - the array to convert
      numSigBytes - the number of significant bytes in your array
      Returns:
      four byte array in Base64 notation.
      Since:
      1.5.1
    • encode3to4

      private static byte[] encode3to4(byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset, int options)

      Encodes up to three bytes of the array source and writes the resulting four Base64 bytes to destination. The source and destination arrays can be manipulated anywhere along their length by specifying srcOffset and destOffset. This method does not check to make sure your arrays are large enough to accommodate srcOffset + 3 for the source array or destOffset + 4 for the destination array. The actual number of significant bytes in your array is given by numSigBytes.

      This is the lowest level of the encoding methods with all possible parameters.

      Parameters:
      source - the array to convert
      srcOffset - the index where conversion begins
      numSigBytes - the number of significant bytes in your array
      destination - the array to hold the conversion
      destOffset - the index where output will be put
      Returns:
      the destination array
      Since:
      1.3
    • encodeBytes

      public static String encodeBytes(byte[] source)
      Encodes a byte array into Base64 notation. Does not GZip-compress data.
      Parameters:
      source - The data to convert
      Returns:
      The data in Base64-encoded form
      Throws:
      IllegalArgumentException - if source array is null
      Since:
      1.4
    • encodeBytes

      public static String encodeBytes(byte[] source, int off, int len, int options) throws IOException
      Encodes a byte array into Base64 notation.

      Example options:

         GZIP: gzip-compresses object before encoding it.
         DO_BREAK_LINES: break lines at 76 characters
           Note: Technically, this makes your encoding non-compliant.
       

      Example: encodeBytes( myData, Base64.GZIP ) or

      Example: encodeBytes( myData, Base64.GZIP | Base64.DO_BREAK_LINES )

      As of v 2.3, if there is an error with the GZIP stream, the method will throw an java.io.IOException. This is new to v2.3! In earlier versions, it just returned a null value, but in retrospect that's a pretty poor way to handle it.

      Parameters:
      source - The data to convert
      off - Offset in array where conversion should begin
      len - Length of data to convert
      options - Specified options
      Returns:
      The Base64-encoded data as a String
      Throws:
      IOException - if there is an error
      IllegalArgumentException - if source array is null, if source array, offset, or length are invalid
      Since:
      2.0
      See Also:
    • encodeBytesToBytes

      public static byte[] encodeBytesToBytes(byte[] source, int off, int len, int options) throws IOException
      Similar to encodeBytes(byte[], int, int, int) but returns a byte array instead of instantiating a String. This is more efficient if you're working with I/O streams and have large data sets to encode.
      Parameters:
      source - The data to convert
      off - Offset in array where conversion should begin
      len - Length of data to convert
      options - Specified options
      Returns:
      The Base64-encoded data as a String
      Throws:
      IOException - if there is an error
      IllegalArgumentException - if source array is null, if source array, offset, or length are invalid
      Since:
      2.3.1
      See Also:
    • decode4to3

      private static int decode4to3(byte[] source, int srcOffset, byte[] destination, int destOffset, int options)
      Decodes four bytes from array source and writes the resulting bytes (up to three of them) to destination. The source and destination arrays can be manipulated anywhere along their length by specifying srcOffset and destOffset. This method does not check to make sure your arrays are large enough to accommodate srcOffset + 4 for the source array or destOffset + 3 for the destination array. This method returns the actual number of bytes that were converted from the Base64 encoding.

      This is the lowest level of the decoding methods with all possible parameters.

      Parameters:
      source - the array to convert
      srcOffset - the index where conversion begins
      destination - the array to hold the conversion
      destOffset - the index where output will be put
      options - alphabet type is pulled from this (standard, url-safe, ordered)
      Returns:
      the number of decoded bytes converted
      Throws:
      IllegalArgumentException - if source or destination arrays are null, if srcOffset or destOffset are invalid or there is not enough room in the array.
      Since:
      1.3