Package android.util

Class Base64

java.lang.Object

android.util.Base64

public class Base64
extends java.lang.Object

Utilities for encoding and decoding the Base64 representation of binary data. See RFCs 2045 and 3548.

Original Author: iharder Reference: http://iharder.sourceforge.net/current/java/base64/

NOTE: Note that the class is updated to to match the android.util.Base64 interface. Since that interface does not follow the Base64 standard this class also does not entirely follow the standard, notably:

• Standard base64 will wrap at 76 characters per default, as per RFC 2045, not only when requested as per RFC 3548.
• Even URL_SAFE encoding will both pad and wrap lines per default, which frankly makes it neither safe for URLs nor filenames.
• Line wrapping will only be applies as a splitter, it will never apply to the end of the encoded string. This is a divergence from the early implementation of the android.util.Base64 class at least.

Field Summary

Fields

Modifier and Type	Field	Description
protected static byte	CR	The new carriage return (\r) as a byte.
static int	CRLF	Encoder flag bit to indicate lines should be terminated with a CRLF pair instead of just an LF.
static int	DEFAULT	Default values for encoder/decoder flags.
protected static byte	EQUALS_SIGN	The equals sign (=) as a byte.
protected static byte	LF	The new line character (\n) as a byte.
protected static int	MAX_LINE_LENGTH	Maximum line length (76) of Base64 output.
static int	NO_CLOSE	Flag to pass to Base64OutputStream to indicate that it should not close the output stream it is wrapping when it itself is closed.
static int	NO_PADDING	Encoder flag bit to omit the padding '=' characters at the end of the output (if any).
static int	NO_WRAP	Do not break lines when encoding.
static int	URL_SAFE	Encoder/decoder flag bit to indicate using the "URL and filename safe" variant of Base64 (see RFC 3548 section 4) where - and _ are used in place of + and /.
protected static byte	WHITE_SPACE_ENC

Method Summary

Modifier and Type	Method	Description
static byte[]	decode(byte[] source, int options)	Decode the Base64-encoded data in input and return the data in a new byte array.
static byte[]	decode(byte[] source, int offset, int len, int options)	Decode the Base64-encoded data in input and return the data in a new byte array.
static byte[]	decode(java.lang.String s, int options)	Decodes data from Base64 notation, automatically detecting gzip-compressed data and decompressing it.
protected static int	decode4to3(byte[] src, int len, byte[] dest, int offset, byte[] decodabet)	Decodes four bytes from array source and writes the resulting bytes (up to three of them) to destination.
static byte[]	encode(byte[] source, int options)	Similar to encodeToString(byte[], int, int, int) but returns a byte array instead of instantiating a String.
static byte[]	encode(byte[] source, int off, int len, int options)	Similar to encodeToString(byte[], int, int, int) but returns a byte array instead of instantiating a String.
protected static int	encode3to4(byte[] source, int srcOffset, int numSigBytes, byte[] destination, int destOffset, boolean noPadding, byte[] alphabet)	Encodes up to three bytes of the array source and writes the resulting four Base64 bytes to destination.
static java.lang.String	encodeToString(byte[] source, int options)	Encodes a byte array into Base64 notation.
static java.lang.String	encodeToString(byte[] source, int off, int len, int options)	Encodes a byte array into Base64 notation.
protected static byte[]	getAlphabet(int options)	Returns one of the _SOMETHING_ALPHABET byte arrays depending on the options specified.
protected 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

DEFAULT

public static final int DEFAULT

Default values for encoder/decoder flags.

See Also:

Constant Field Values

NO_PADDING

public static final int NO_PADDING

Encoder flag bit to omit the padding '=' characters at the end of the output (if any).

See Also:

Constant Field Values

NO_WRAP

public static final int NO_WRAP

Do not break lines when encoding. Value is 2.

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Constant Field Values

CRLF

public static final int CRLF

Encoder flag bit to indicate lines should be terminated with a CRLF pair instead of just an LF. Has no effect if NO_WRAP is specified as well.

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Constant Field Values

URL_SAFE

public static final int URL_SAFE

Encoder/decoder flag bit to indicate using the "URL and filename safe" variant of Base64 (see RFC 3548 section 4) where - and _ are used in place of + and /. URL_SAFE implies NO_WRAP and NO_PADDING.

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Constant Field Values

NO_CLOSE

public static final int NO_CLOSE

Flag to pass to Base64OutputStream to indicate that it should not close the output stream it is wrapping when it itself is closed.

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Constant Field Values

MAX_LINE_LENGTH

protected static final int MAX_LINE_LENGTH

Maximum line length (76) of Base64 output.

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Constant Field Values

EQUALS_SIGN

protected static final byte EQUALS_SIGN

The equals sign (=) as a byte.

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Constant Field Values

CR

protected static final byte CR

The new carriage return (\r) as a byte.

See Also:

Constant Field Values

LF

protected static final byte LF

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

See Also:

Constant Field Values

WHITE_SPACE_ENC

protected static final byte WHITE_SPACE_ENC

See Also:

Constant Field Values

Method Detail

getAlphabet

protected static 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.

Parameters:

options - Option used to determine alphabet.

Returns:

The alphabet pos to byte value array.

getDecodabet

protected static 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.

Parameters:

options - Option used to determine decodabet.

Returns:

The decodabet pos to byte value array.

encode3to4

protected static int encode3to4(byte[] source,
                                int srcOffset,
                                int numSigBytes,
                                byte[] destination,
                                int destOffset,
                                boolean noPadding,
                                byte[] alphabet)

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

noPadding - True if no padding should be added.

alphabet - The alphabet to use.

Returns:

the destination array

Since:

1.3

encodeToString

public static java.lang.String encodeToString(byte[] source,
                                              int options)

Encodes a byte array into Base64 notation.

Parameters:

source - The data to convert

options - Specified options

Returns:

The Base64-encoded data as a String

Throws:

java.lang.NullPointerException - if source array is null

Since:

2.0

See Also:

NO_WRAP

encodeToString

public static java.lang.String encodeToString(byte[] source,
                                              int off,
                                              int len,
                                              int options)

Encodes a byte array into Base64 notation.

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.lang.NullPointerException - if source array is null

java.lang.IllegalArgumentException - if source array, offset, or length are invalid

Since:

2.0

See Also:

NO_WRAP

encode

public static byte[] encode(byte[] source,
                            int off,
                            int len,
                            int options)

Similar to encodeToString(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 encodeToString.

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.lang.NullPointerException - if source array is null

java.lang.IllegalArgumentException - if source array, offset, or length are invalid

Since:

2.3.1

See Also:

NO_WRAP, URL_SAFE, CRLF

encode

public static byte[] encode(byte[] source,
                            int options)

Similar to encodeToString(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 encodeToString.

Parameters:

source - The data to convert

options - Specified options

Returns:

The Base64-encoded data as a String

Throws:

java.lang.NullPointerException - if source array is null

java.lang.IllegalArgumentException - if source array, offset, or length are invalid

Since:

2.3.1

See Also:

NO_WRAP

decode4to3

protected static int decode4to3(byte[] src,
                                int len,
                                byte[] dest,
                                int offset,
                                byte[] decodabet)

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:

src - the array to convert

len - The number of bytes to read within src.

dest - the array to hold the conversion

offset - the index where output will be put

decodabet - alphabet type is pulled from this (standard, url-safe, ordered)

Returns:

the number of decoded bytes converted

Throws:

java.lang.NullPointerException - if source or destination arrays are null

java.lang.IllegalArgumentException - if srcOffset or destOffset are invalid or there is not enough room in the array.

Since:

1.3

decode

public static byte[] decode(byte[] source,
                            int options)

Decode the Base64-encoded data in input and return the data in a new byte array. The padding '=' characters at the end are considered optional, but if any are present, there must be the correct number of them.

Parameters:

source - The data to decode

options - controls certain features of the decoded output. Pass DEFAULT to decode standard Base64.

Returns:

decoded data

decode

public static byte[] decode(byte[] source,
                            int offset,
                            int len,
                            int options)

Decode the Base64-encoded data in input and return the data in a new byte array. The padding '=' characters at the end are considered optional, but if any are present, there must be the correct number of them.

Parameters:

source - The data to decode

offset - The offset within the input array at which to start

len - The number of byte sof input to decode.

options - controls certain features of the decoded output. Pass DEFAULT to decode standard Base64.

Returns:

decoded data

decode

public static byte[] decode(java.lang.String s,
                            int options)

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

Parameters:

s - the string to decode

options - encodeToString options such as URL_SAFE

Returns:

the decoded data

Throws:

java.lang.NullPointerException - if s is null