org.jhotdraw.io
Class Base64

java.lang.Object
  extended by org.jhotdraw.io.Base64

public class Base64
extends java.lang.Object

Encodes and decodes to and from Base64 notation.

Change Log:

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:
$Id: Base64.java 527 2009-06-07 14:28:19Z rawcoder $
Author:
Robert Harder, rob@iharder.net

Nested Class Summary
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
private static byte[] _NATIVE_ALPHABET
           
private static byte[] ALPHABET
          The 64 valid Base64 values.
private static byte[] DECODABET
          Translates a Base64 value to either its 6-bit reconstruction value or a negative number indicating some other meaning.
static int DECODE
          Specify decoding.
static int DONT_BREAK_LINES
          Don't break lines when encoding (violates strict Base64 specification)
static int ENCODE
          Specify encoding.
private static byte EQUALS_SIGN
          The equals sign (=) as a byte.
private static byte EQUALS_SIGN_ENC
           
static int GZIP
          Specify that data should be gzip-compressed.
private static int MAX_LINE_LENGTH
          Maximum line length (76) of Base64 output.
private static byte NEW_LINE
          The new line character (\n) as a byte.
static int NO_OPTIONS
          No options specified.
private static java.lang.String PREFERRED_ENCODING
          Preferred encoding.
private static byte WHITE_SPACE_ENC
           
 
Constructor Summary
private Base64()
          Defeats instantiation.
 
Method Summary
static byte[] decode(byte[] source, int off, int len)
          Very low-level access to decoding ASCII characters in the form of a byte array.
static byte[] decode(java.lang.String s)
          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)
          Decodes four bytes from array source and writes the resulting bytes (up to three of them) to destination.
static byte[] decodeFromFile(java.lang.String filename)
          Convenience method for reading a base64-encoded file and decoding it.
static boolean decodeToFile(java.lang.String dataToDecode, java.lang.String filename)
          Convenience method for decoding data to a file.
static java.lang.Object decodeToObject(java.lang.String encodedObject)
          Attempts to decode Base64 data and deserialize a Java Object within.
private static byte[] encode3to4(byte[] b4, byte[] threeBytes, int numSigBytes)
          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)
          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 options)
          Encodes a byte array into Base64 notation.
static java.lang.String encodeBytes(byte[] source, int off, int len)
          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 java.lang.String encodeFromFile(java.lang.String filename)
          Convenience method for reading a binary file and base64-encoding it.
static java.lang.String encodeObject(java.io.Serializable serializableObject)
          Serializes an object and returns the Base64-encoded version of that serialized object.
static java.lang.String encodeObject(java.io.Serializable serializableObject, int options)
          Serializes an object and returns the Base64-encoded version of that serialized object.
static boolean encodeToFile(byte[] dataToEncode, java.lang.String filename)
          Convenience method for encoding data to a file.
 
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.

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

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

ALPHABET

private static final byte[] ALPHABET
The 64 valid Base64 values.


_NATIVE_ALPHABET

private static final byte[] _NATIVE_ALPHABET

DECODABET

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


WHITE_SPACE_ENC

private static final byte WHITE_SPACE_ENC
See Also:
Constant Field Values

EQUALS_SIGN_ENC

private static final byte EQUALS_SIGN_ENC
See Also:
Constant Field Values
Constructor Detail

Base64

private Base64()
Defeats instantiation.

Method Detail

encode3to4

private static byte[] encode3to4(byte[] b4,
                                 byte[] threeBytes,
                                 int numSigBytes)
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)
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.

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 java.lang.String encodeObject(java.io.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 java.lang.String encodeObject(java.io.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 java.lang.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 java.lang.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 java.lang.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 java.lang.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
Since:
2.0
See Also:
GZIP, DONT_BREAK_LINES

decode4to3

private static int decode4to3(byte[] source,
                              int srcOffset,
                              byte[] destination,
                              int destOffset)
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.

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
Returns:
the number of decoded bytes converted
Since:
1.3

decode

public static byte[] decode(byte[] source,
                            int off,
                            int len)
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(java.lang.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

decodeToObject

public static java.lang.Object decodeToObject(java.lang.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,
                                   java.lang.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(java.lang.String dataToDecode,
                                   java.lang.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(java.lang.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 java.lang.String encodeFromFile(java.lang.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