codec
Class Base64

java.lang.Object
  codec.Base64

public class Base64
extends Object

Encodes and decodes data according to Base64 encoding as described in RFC 1521. Encoded data is broken into lines of 76 charcters each (19 groups of 4 characters which represent 3 bytes of input per group.

The three input bytes are divided into four groups of six bits each which are encoded according to the table base64 given below.

Version:

"$Id: Base64.java 1913 2007-08-08 02:41:53Z jpeters $"

Author:

Volker Roth

Field Summary

private static char[]	base64 The basic Base64 encoding table.
private static byte	F Marks an entry in the decoding table as an invalid code character.
private static String	hex Used to transform bytes into a hexadecimal string representation - basically a convenience method which facilitates debugging and verification.
private static byte	PAD Marks the pad character '=' in the decoding table.
private static char	pad1 If the input is congruent 2 modulo 3 then one pad character is required.
private static String	pad2 If the input is congruent 1 modulo 3 then two pad characters are required.
private static byte[]	reverse The table reverse serves to transform encoded characters back into the corresponding six bit values efficiently.

Constructor Summary

private

Base64() This class is never instantiated; use the class methods instead.

Method Summary

static byte[]	decode(byte[] code) Decodes a given byte array containing Unicode BASE_LATIN encoded characters with one byte encoding per character.
static byte[]	decode(String input) Decodes a Base64 encoded string into an array of bytes with exactly the length of the encoded data.
static String	encode(byte[] input) Encodes the input array of bytes into a Base64 encoded string with padding if required.
static String	toHex(byte[] b) Encodes a byte array into a hexadecimal string representation.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

base64

private static final char[] base64

The basic Base64 encoding table. The index into the string is the value being encoded with the corresponding character.

pad1

private static char pad1

If the input is congruent 2 modulo 3 then one pad character is required.

pad2

private static String pad2

If the input is congruent 1 modulo 3 then two pad characters are required.

F

private static final byte F

Marks an entry in the decoding table as an invalid code character.

See Also:

Constant Field Values

PAD

private static final byte PAD

Marks the pad character '=' in the decoding table.

See Also:

Constant Field Values

reverse

private static final byte[] reverse

The table reverse serves to transform encoded characters back into the corresponding six bit values efficiently.

hex

private static final String hex

Used to transform bytes into a hexadecimal string representation - basically a convenience method which facilitates debugging and verification.

See Also:

Constant Field Values

Constructor Detail

Base64

private Base64()

This class is never instantiated; use the class methods instead.

Method Detail

encode

public static String encode(byte[] input)

Encodes the input array of bytes into a Base64 encoded string with padding if required. The output is not broken into lines.

Parameters:

input - The byte array to be encoded.

Returns:

The Base64 encoded String representing the input byte array.

decode

public static byte[] decode(String input)
                     throws CorruptedCodeException

Decodes a Base64 encoded string into an array of bytes with exactly the length of the encoded data. The encoded string may contain arbitrarily much garbage data in the form of control sequences and non-base64 characters as long as the local charcter encoding is Unicode BASE_LATIN.

Parameters:

input - The encoded Base64 character String.

Returns:

The decoded data.

Throws:

CorruptedCodeException - if the Base64 code contains errors such as a missing character or bad padding.

decode

public static byte[] decode(byte[] code)
                     throws CorruptedCodeException

Decodes a given byte array containing Unicode BASE_LATIN encoded characters with one byte encoding per character. The array is garbled in the course of the decoding, because it is partly overwritten with the six Bit groups represented by the code letters! This method is used by the decoding method byte[] decode(String).

Parameters:

code - The BASE_LATIN Base64 encoded input with one byte per character.

Returns:

The byte array containing the decoded data. The array has the exact length of the decoded data.

Throws:

CorruptedCodeException - if the decoding process revealed errors such as bad padding or missing charcters.

toHex

public static String toHex(byte[] b)

Encodes a byte array into a hexadecimal string representation.

Parameters:

b - The input byte array.

Returns:

The string with the hexadecimal representation.