Class Base64

java.lang.Object
com.aowagie.text.pdf.codec.Base64

public class Base64 extends Object

Encodes and decodes to and from Base64 notation.

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

Change Log:

  • 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:
2.2.1
  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    private static class 
    A Base64.InputStream will read data from another java.io.InputStream, given in the constructor, and encode/decode to/from Base64 notation on the fly.
    private 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 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.
    private static final int
    Specify decoding.
    private static final int
    Don't break lines when encoding (violates strict Base64 specification)
    private static final int
    Specify encoding.
    private static final byte
    The equals sign (=) as a byte.
    private static final byte
     
    private static final int
    Specify that data should be gzip-compressed.
    private static final int
    Maximum line length (76) of Base64 output.
    private static final byte
    The new line character (\n) as a byte.
    private static final int
    No options specified.
    private 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.
    private 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 byte[]
    decode(byte[] source, int off, int len, int options)
    Very low-level access to decoding ASCII characters in the form of a byte array.
    static byte[]
    Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.
    private static byte[]
    decode(String s, int options)
    Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.
    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 void
    decodeFileToFile(String infile, String outfile)
    Reads infile and decodes it to outfile.
    private static byte[]
    Convenience method for reading a base64-encoded file and decoding it.
    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.
    private static String
    encodeBytes(byte[] source, int off, int len, int options)
    Encodes a byte array into Base64 notation.
    private static void
    encodeFileToFile(String infile, String outfile)
    Reads infile and encodes it to outfile.
    private static String
    Convenience method for reading a binary file and base64-encoding it.
    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.
    static final void
    main(String[] args)
    Encodes or decodes two files from the command line; feel free to delete this method (in fact you probably should) if you're embedding this code into a larger program.
    private static final void
    Prints command line usage.

    Methods inherited from class java.lang.Object

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

    • NO_OPTIONS

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

      private static final int ENCODE
      Specify encoding.
      See Also:
    • DECODE

      private static final int DECODE
      Specify decoding.
      See Also:
    • GZIP

      private static final int GZIP
      Specify that data should be gzip-compressed.
      See Also:
    • DONT_BREAK_LINES

      private static final int DONT_BREAK_LINES
      Don't break lines when encoding (violates strict Base64 specification)
      See Also:
    • URL_SAFE

      private 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

      private 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.
    • WHITE_SPACE_ENC

      private static final byte WHITE_SPACE_ENC
      See Also:
    • EQUALS_SIGN_ENC

      private static final byte EQUALS_SIGN_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 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.
    • main

      public static final void main(String[] args)
      Encodes or decodes two files from the command line; feel free to delete this method (in fact you probably should) if you're embedding this code into a larger program.
      Parameters:
      args - args to send
    • usage

      private static final void usage(String msg)
      Prints command line usage.
      Parameters:
      msg - A message to include with usage info.
    • 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 accomodate 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:
      a encode String
      Since:
      1.4
    • encodeBytes

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

      Valid options:

         GZIP: gzip-compresses object before encoding it.
         DONT_BREAK_LINES: don't 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.DONT_BREAK_LINES )

      Parameters:
      source - The data to convert
      off - Offset in array where conversion should begin
      len - Length of data to convert
      options - Specified options alphabet type is pulled from this (standard, url-safe, ordered)
      Since:
      2.0
      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 accomodate 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
      Since:
      1.3
    • decode

      private static byte[] decode(byte[] source, int off, int len, int options)
      Very low-level access to decoding ASCII characters in the form of a byte array. Does not support automatically gunzipping or any other "fancy" features.
      Parameters:
      source - The Base64 encoded data
      off - The offset of where to begin decoding
      len - The length of characters to decode
      Returns:
      decoded data
      Since:
      1.3
    • decode

      public static byte[] decode(String s)
      Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.
      Parameters:
      s - the string to decode
      Returns:
      the decoded data
      Since:
      1.4
    • decode

      private static byte[] decode(String s, int options)
      Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.
      Parameters:
      s - the string to decode
      options - encode options such as URL_SAFE
      Returns:
      the decoded data
      Since:
      1.4
    • decodeFromFile

      private static byte[] decodeFromFile(String filename)
      Convenience method for reading a base64-encoded file and decoding it.
      Parameters:
      filename - Filename for reading encoded data
      Returns:
      decoded byte array or null if unsuccessful
      Since:
      2.1
    • encodeFromFile

      private static String encodeFromFile(String filename)
      Convenience method for reading a binary file and base64-encoding it.
      Parameters:
      filename - Filename for reading binary data
      Returns:
      base64-encoded string or null if unsuccessful
      Since:
      2.1
    • encodeFileToFile

      private static void encodeFileToFile(String infile, String outfile)
      Reads infile and encodes it to outfile.
      Parameters:
      infile - Input file
      outfile - Output file
      Since:
      2.2
    • decodeFileToFile

      private static void decodeFileToFile(String infile, String outfile)
      Reads infile and decodes it to outfile.
      Parameters:
      infile - Input file
      outfile - Output file
      Since:
      2.2