Class Base64


  • public class Base64
    extends java.lang.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  Base64.OutputStream
      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.
    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private Base64()
      Defeats instantiation.
    • Method Summary

      All Methods Static Methods Concrete Methods 
      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 java.lang.String encodeBytes​(byte[] source)
      Encodes a byte array into Base64 notation.
      static java.lang.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 byte[] getAlphabet​(int options)
      Returns one of the _SOMETHING_ALPHABET byte arrays depending on the options specified.
      private static 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 Detail

      • NO_OPTIONS

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

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

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

        public static final int DO_BREAK_LINES
        Do break lines when encoding. Value is 8.
        See Also:
        Constant Field Values
      • 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:
        Constant Field Values
      • MAX_LINE_LENGTH

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

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

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

        private static final java.lang.String PREFERRED_ENCODING
        Preferred encoding.
        See Also:
        Constant Field Values
      • _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 Detail

      • Base64

        private Base64()
        Defeats instantiation.
    • Method Detail

      • 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 java.lang.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:
        java.lang.IllegalArgumentException - if source array is null
        Since:
        1.4
      • encodeBytes

        public static java.lang.String encodeBytes​(byte[] source,
                                                   int off,
                                                   int len,
                                                   int options)
                                            throws java.io.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:
        java.io.IOException - if there is an error
        java.lang.IllegalArgumentException - if source array is null, if source array, offset, or length are invalid
        Since:
        2.0
        See Also:
        GZIP, DO_BREAK_LINES
      • encodeBytesToBytes

        public static byte[] encodeBytesToBytes​(byte[] source,
                                                int off,
                                                int len,
                                                int options)
                                         throws java.io.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:
        java.io.IOException - if there is an error
        java.lang.IllegalArgumentException - if source array is null, if source array, offset, or length are invalid
        Since:
        2.3.1
        See Also:
        GZIP, DO_BREAK_LINES
      • 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:
        java.lang.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