org.cdlib.mrt.security.Base64

public class Base64 extends Object

Encodes and decodes to and from Base64 notation.

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 (though that breaks strict Base64 compatibility), and encoding using the URL-safe and Ordered dialects.

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.DONT_BREAK_LINES );

to compress the data before encoding it and then making the output have no newline characters.

Change Log:

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).
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:: 2.2.2
Author:: Robert Harder, rob@iharder.net

Nested Class Summary

Nested Classes

Modifier and Type

Class

Description

static class

Base64.InputStream

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.

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.
Field Summary

Fields

Modifier and Type

Field

Description

protected 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.

protected static final byte[]

_ORDERED_DECODABET

Used in decoding the "ordered" dialect of Base64.

protected static final byte[]

_STANDARD_DECODABET

Translates a Base64 value to either its 6-bit reconstruction value or a negative number indicating some other meaning.

protected 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.

protected static final byte[]

_URL_SAFE_DECODABET

Used in decoding URL- and Filename-safe dialects of Base64.

static final int

DECODE

Specify decoding.

static final int

DONT_BREAK_LINES

Don't break lines when encoding (violates strict Base64 specification)

static final int

ENCODE

Specify encoding.

protected static final byte

EQUALS_SIGN

The equals sign (=) as a byte.

protected static final byte

EQUALS_SIGN_ENC

static final int

GZIP

Specify that data should be gzip-compressed.

protected static final int

MAX_LINE_LENGTH

Maximum line length (76) of Base64 output.

protected static final byte

NEW_LINE

The new line character (\n) as a byte.

static final int

NO_OPTIONS

No options specified.

static final int

ORDERED

Encode using the special "ordered" dialect of Base64 described here: http://www.faqs.org/qa/rfcc-1940.html.

protected static final String

PREFERRED_ENCODING

Preferred encoding.

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.

protected static final byte

WHITE_SPACE_ENC
Constructor Summary

Constructors

Modifier

Constructor

Description

protected

Base64()

Defeats instantiation.
Method Summary

Modifier and Type

Method

Description

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[]

decode(String s)

Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.

static byte[]

decode(String s, int options)

Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.

protected 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.

static boolean

decodeFileToFile(String infile, String outfile)

Reads infile and decodes it to outfile.

static byte[]

decodeFromFile(String filename)

Convenience method for reading a base64-encoded file and decoding it.

static boolean

decodeToFile(String dataToDecode, String filename)

Convenience method for decoding data to a file.

static Object

decodeToObject(String encodedObject)

Attempts to decode Base64 data and deserialize a Java Object within.

protected 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.

protected 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 options)

Encodes a byte array into Base64 notation.

static String

encodeBytes(byte[] source, int off, int len)

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 boolean

encodeFileToFile(String infile, String outfile)

Reads infile and encodes it to outfile.

static String

encodeFromFile(String filename)

Convenience method for reading a binary file and base64-encoding it.

static String

encodeObject(Serializable serializableObject)

Serializes an object and returns the Base64-encoded version of that serialized object.

static String

encodeObject(Serializable serializableObject, int options)

Serializes an object and returns the Base64-encoded version of that serialized object.

static boolean

encodeToFile(byte[] dataToEncode, String filename)

Convenience method for encoding data to a file.

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.

protected static final void

usage(String msg)

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
  
  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.
  See Also:
  
  Constant Field Values
- DECODE
  
  public static final int DECODE
  
  Specify decoding.
  See Also:
  
  Constant Field Values
- GZIP
  
  public static final int GZIP
  
  Specify that data should be gzip-compressed.
  See Also:
  
  Constant Field Values
- DONT_BREAK_LINES
  
  public static final int DONT_BREAK_LINES
  
  Don't break lines when encoding (violates strict Base64 specification)
  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
- 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:
  
  Constant Field Values
- MAX_LINE_LENGTH
  
  protected static final int MAX_LINE_LENGTH
  
  Maximum line length (76) of Base64 output.
  See Also:
  
  Constant Field Values
- EQUALS_SIGN
  
  protected static final byte EQUALS_SIGN
  
  The equals sign (=) as a byte.
  See Also:
  
  Constant Field Values
- NEW_LINE
  
  protected static final byte NEW_LINE
  
  The new line character (\n) as a byte.
  See Also:
  
  Constant Field Values
- PREFERRED_ENCODING
  
  protected static final String PREFERRED_ENCODING
  
  Preferred encoding.
  See Also:
  
  Constant Field Values
- WHITE_SPACE_ENC
  
  protected static final byte WHITE_SPACE_ENC
  See Also:
  
  Constant Field Values
- EQUALS_SIGN_ENC
  
  protected static final byte EQUALS_SIGN_ENC
  See Also:
  
  Constant Field Values
- _STANDARD_DECODABET
  
  protected 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
  
  protected 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
  
  protected static final byte[] _URL_SAFE_DECODABET
  
  Used in decoding URL- and Filename-safe dialects of Base64.
- _ORDERED_ALPHABET
  
  protected 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
  
  protected static final byte[] _ORDERED_DECODABET
  
  Used in decoding the "ordered" dialect of Base64.
Constructor Details
- Base64
  
  protected Base64()
  
  Defeats instantiation.
Method Details
- 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.
- usage
  
  protected static final void usage(String msg)
  
  Prints command line usage.
  
  Parameters:
  
  msg - A message to include with usage info.
- encode3to4
  
  protected 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
  
  protected 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
- encodeObject
  
  public static String encodeObject(Serializable serializableObject)
  
  Serializes an object and returns the Base64-encoded version of that serialized object. If the object cannot be serialized or there is another error, the method will return null. The object is not GZip-compressed before being encoded.
  
  Parameters:
  
  serializableObject - The object to encode
  
  Returns:
  
  The Base64-encoded object
  
  Since:
  
  1.4
- encodeObject
  
  public static String encodeObject(Serializable serializableObject, int options)
  Serializes an object and returns the Base64-encoded version of that serialized object. If the object cannot be serialized or there is another error, the method will return null.
  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: encodeObject( myObj, Base64.GZIP ) or
  Example: encodeObject( myObj, Base64.GZIP | Base64.DONT_BREAK_LINES )
  Parameters:
  
  serializableObject - The object to encode
  
  options - Specified options
  
  Returns:
  
  The Base64-encoded object
  
  Since:
  
  2.0
  
  See Also:
  
  GZIP
  
  DONT_BREAK_LINES
- 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
  
  Since:
  
  1.4
- encodeBytes
  
  public static String encodeBytes(byte[] source, 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
  
  options - Specified options
  
  Since:
  
  2.0
  
  See Also:
  
  GZIP
  
  DONT_BREAK_LINES
- encodeBytes
  
  public static String encodeBytes(byte[] source, int off, int len)
  
  Encodes a byte array into Base64 notation. Does not GZip-compress data.
  
  Parameters:
  
  source - The data to convert
  
  off - Offset in array where conversion should begin
  
  len - Length of data to convert
  
  Since:
  
  1.4
- encodeBytes
  
  public 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
  
  options - alphabet type is pulled from this (standard, url-safe, ordered)
  
  Since:
  
  2.0
  
  See Also:
  
  GZIP
  
  DONT_BREAK_LINES
- decode4to3
  
  protected 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
  
  public 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
  
  public 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
- decodeToObject
  
  public static Object decodeToObject(String encodedObject)
  
  Attempts to decode Base64 data and deserialize a Java Object within. Returns null if there was an error.
  
  Parameters:
  
  encodedObject - The Base64 data to decode
  
  Returns:
  
  The decoded and deserialized object
  
  Since:
  
  1.5
- encodeToFile
  
  public static boolean encodeToFile(byte[] dataToEncode, String filename)
  
  Convenience method for encoding data to a file.
  
  Parameters:
  
  dataToEncode - byte array of data to encode in base64 form
  
  filename - Filename for saving encoded data
  
  Returns:
  
  true if successful, false otherwise
  
  Since:
  
  2.1
- decodeToFile
  
  public static boolean decodeToFile(String dataToDecode, String filename)
  
  Convenience method for decoding data to a file.
  
  Parameters:
  
  dataToDecode - Base64-encoded data as a string
  
  filename - Filename for saving decoded data
  
  Returns:
  
  true if successful, false otherwise
  
  Since:
  
  2.1
- decodeFromFile
  
  public 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
  
  public 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
  
  public static boolean encodeFileToFile(String infile, String outfile)
  
  Reads infile and encodes it to outfile.
  
  Parameters:
  
  infile - Input file
  
  outfile - Output file
  
  Returns:
  
  true if the operation is successful
  
  Since:
  
  2.2
- decodeFileToFile
  
  public static boolean decodeFileToFile(String infile, String outfile)
  
  Reads infile and decodes it to outfile.
  
  Parameters:
  
  infile - Input file
  
  outfile - Output file
  
  Returns:
  
  true if the operation is successful
  
  Since:
  
  2.2

Class Base64

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Details

NO_OPTIONS

ENCODE

DECODE

GZIP

DONT_BREAK_LINES

URL_SAFE

ORDERED

MAX_LINE_LENGTH

EQUALS_SIGN

NEW_LINE

PREFERRED_ENCODING

WHITE_SPACE_ENC

EQUALS_SIGN_ENC

_STANDARD_DECODABET

_URL_SAFE_ALPHABET

_URL_SAFE_DECODABET

_ORDERED_ALPHABET

_ORDERED_DECODABET

Constructor Details

Base64

Method Details

main

usage

encode3to4

encode3to4

encodeObject

encodeObject

encodeBytes

encodeBytes

encodeBytes

encodeBytes

decode4to3

decode

decode

decode

decodeToObject

encodeToFile

decodeToFile

decodeFromFile

encodeFromFile

encodeFileToFile

decodeFileToFile