Package org.apache.commons.codec.binary

Class BaseNCodec

java.lang.Object

org.apache.commons.codec.binary.BaseNCodec

All Implemented Interfaces:

BinaryDecoder, BinaryEncoder, Decoder, Encoder

Direct Known Subclasses:

Base16, Base32, Base64

public abstract class BaseNCodec
extends Object
implements BinaryEncoder, BinaryDecoder

Abstract superclass for Base-N encoders and decoders.

This class is thread-safe.

You can set the decoding behavior when the input bytes contain leftover trailing bits that cannot be created by a valid encoding. These can be bits that are unused from the final character or entire characters. The default mode is lenient decoding.

• Lenient: Any trailing bits are composed into 8-bit bytes where possible. The remainder are discarded.
• Strict: The decoding will raise an IllegalArgumentException if trailing bits are not part of a valid encoding. Any unused bits from the final character must be zero. Impossible counts of entire final characters are not allowed.

When strict decoding is enabled it is expected that the decoded bytes will be re-encoded to a byte array that matches the original, i.e. no changes occur on the final character. This requires that the input bytes use the same padding and alphabet as the encoder.

Field Summary

Fields

Modifier and Type	Field	Description
protected static final CodecPolicy	DECODING_POLICY_DEFAULT	The default decoding policy.
protected final int	lineLength	Chunksize for encoding.
protected static final int	MASK_8BITS	Mask used to extract 8 bits, used in decoding bytes
static final int	MIME_CHUNK_SIZE	MIME chunk size per RFC 2045 section 6.8.
protected final byte	pad	Pad byte.
protected final byte	PAD	Deprecated. Use pad.
protected static final byte	PAD_DEFAULT	Byte used to pad output.
static final int	PEM_CHUNK_SIZE	PEM chunk size per RFC 1421 section 4.3.2.4.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	BaseNCodec(int unencodedBlockSize, int encodedBlockSize, int lineLength, int chunkSeparatorLength)	Note lineLength is rounded down to the nearest multiple of the encoded block size.
protected	BaseNCodec(int unencodedBlockSize, int encodedBlockSize, int lineLength, int chunkSeparatorLength, byte pad)	Note lineLength is rounded down to the nearest multiple of the encoded block size.
protected	BaseNCodec(int unencodedBlockSize, int encodedBlockSize, int lineLength, int chunkSeparatorLength, byte pad, CodecPolicy decodingPolicy)	Note lineLength is rounded down to the nearest multiple of the encoded block size.

Method Summary

Modifier and Type	Method	Description
protected boolean	containsAlphabetOrPad(byte[] arrayOctet)	Tests a given byte array to see if it contains any characters within the alphabet or PAD.
byte[]	decode(byte[] pArray)	Decodes a byte[] containing characters in the Base-N alphabet.
Object	decode(Object obj)	Decodes an Object using the Base-N algorithm.
byte[]	decode(String pArray)	Decodes a String containing characters in the Base-N alphabet.
byte[]	encode(byte[] pArray)	Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
byte[]	encode(byte[] pArray, int offset, int length)	Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.
Object	encode(Object obj)	Encodes an Object using the Base-N algorithm.
String	encodeAsString(byte[] pArray)	Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet.
String	encodeToString(byte[] pArray)	Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet.
protected byte[]	ensureBufferSize(int size, org.apache.commons.codec.binary.BaseNCodec.Context context)	Ensure that the buffer has room for size bytes
static byte[]	getChunkSeparator()	Gets a copy of the chunk separator per RFC 2045 section 2.1.
CodecPolicy	getCodecPolicy()	Returns the decoding behavior policy.
protected int	getDefaultBufferSize()	Gets the default buffer size.
long	getEncodedLength(byte[] pArray)	Calculates the amount of space needed to encode the supplied array.
protected abstract boolean	isInAlphabet(byte value)	Returns whether or not the octet is in the current alphabet.
boolean	isInAlphabet(byte[] arrayOctet, boolean allowWSPad)	Tests a given byte array to see if it contains only valid characters within the alphabet.
boolean	isInAlphabet(String basen)	Tests a given String to see if it contains only valid characters within the alphabet.
boolean	isStrictDecoding()	Returns true if decoding behavior is strict.
protected static boolean	isWhiteSpace(byte byteToCheck)	Deprecated. Use Character.isWhitespace(int).

Methods inherited from class java.lang.Object

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

Field Details

MIME_CHUNK_SIZE

public static final int MIME_CHUNK_SIZE

MIME chunk size per RFC 2045 section 6.8.

The 76 character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.

See Also:

• RFC 2045 section 6.8
• Constant Field Values

PEM_CHUNK_SIZE

public static final int PEM_CHUNK_SIZE

PEM chunk size per RFC 1421 section 4.3.2.4.

The 64 character limit does not count the trailing CRLF, but counts all other characters, including any equal signs.

See Also:

• RFC 1421 section 4.3.2.4
• Constant Field Values

MASK_8BITS

protected static final int MASK_8BITS

Mask used to extract 8 bits, used in decoding bytes

See Also:

• Constant Field Values

PAD_DEFAULT

protected static final byte PAD_DEFAULT

Byte used to pad output.

See Also:

• Constant Field Values

DECODING_POLICY_DEFAULT

protected static final CodecPolicy DECODING_POLICY_DEFAULT

The default decoding policy.

Since:

1.15

PAD

@Deprecated
protected final byte PAD

Deprecated.

Use pad. Will be removed in 2.0.

See Also:

• Constant Field Values

pad

protected final byte pad

Pad byte. Instance variable just in case it needs to vary later.

lineLength

protected final int lineLength

Chunksize for encoding. Not used when decoding. A value of zero or less implies no chunking of the encoded data. Rounded down to the nearest multiple of encodedBlockSize.

Constructor Details

BaseNCodec

protected BaseNCodec(int unencodedBlockSize,
 int encodedBlockSize,
 int lineLength,
 int chunkSeparatorLength)

Note lineLength is rounded down to the nearest multiple of the encoded block size. If chunkSeparatorLength is zero, then chunking is disabled.

Parameters:

unencodedBlockSize - the size of an unencoded block (e.g. Base64 = 3)

encodedBlockSize - the size of an encoded block (e.g. Base64 = 4)

lineLength - if > 0, use chunking with a length lineLength

chunkSeparatorLength - the chunk separator length, if relevant

BaseNCodec

protected BaseNCodec(int unencodedBlockSize,
 int encodedBlockSize,
 int lineLength,
 int chunkSeparatorLength,
 byte pad)

Note lineLength is rounded down to the nearest multiple of the encoded block size. If chunkSeparatorLength is zero, then chunking is disabled.

Parameters:

unencodedBlockSize - the size of an unencoded block (e.g. Base64 = 3)

encodedBlockSize - the size of an encoded block (e.g. Base64 = 4)

lineLength - if > 0, use chunking with a length lineLength

chunkSeparatorLength - the chunk separator length, if relevant

pad - byte used as padding byte.

BaseNCodec

protected BaseNCodec(int unencodedBlockSize,
 int encodedBlockSize,
 int lineLength,
 int chunkSeparatorLength,
 byte pad,
 CodecPolicy decodingPolicy)

Note lineLength is rounded down to the nearest multiple of the encoded block size. If chunkSeparatorLength is zero, then chunking is disabled.

Parameters:

unencodedBlockSize - the size of an unencoded block (e.g. Base64 = 3)

encodedBlockSize - the size of an encoded block (e.g. Base64 = 4)

lineLength - if > 0, use chunking with a length lineLength

chunkSeparatorLength - the chunk separator length, if relevant

pad - byte used as padding byte.

decodingPolicy - Decoding policy.

Since:

1.15

Method Details

getChunkSeparator

public static byte[] getChunkSeparator()

Gets a copy of the chunk separator per RFC 2045 section 2.1.

Returns:

the chunk separator

Since:

1.15

See Also:

• RFC 2045 section 2.1

isWhiteSpace

@Deprecated
protected static boolean isWhiteSpace(byte byteToCheck)

Deprecated.

Use Character.isWhitespace(int).

Checks if a byte value is whitespace or not.

Parameters:

byteToCheck - the byte to check

Returns:

true if byte is whitespace, false otherwise

See Also:

• Character.isWhitespace(int)

containsAlphabetOrPad

protected boolean containsAlphabetOrPad(byte[] arrayOctet)

Tests a given byte array to see if it contains any characters within the alphabet or PAD. Intended for use in checking line-ending arrays

Parameters:

arrayOctet - byte array to test

Returns:

true if any byte is a valid character in the alphabet or PAD; false otherwise

decode

public byte[] decode(byte[] pArray)

Decodes a byte[] containing characters in the Base-N alphabet.

Specified by:

decode in interface BinaryDecoder

Parameters:

pArray - A byte array containing Base-N character data

Returns:

a byte array containing binary data

decode

public Object decode(Object obj)
              throws DecoderException

Decodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of the Decoder interface, and will throw a DecoderException if the supplied object is not of type byte[] or String.

Specified by:

decode in interface Decoder

Parameters:

obj - Object to decode

Returns:

An object (of type byte[]) containing the binary data which corresponds to the byte[] or String supplied.

Throws:

DecoderException - if the parameter supplied is not of type byte[]

decode

public byte[] decode(String pArray)

Decodes a String containing characters in the Base-N alphabet.

Parameters:

pArray - A String containing Base-N character data

Returns:

a byte array containing binary data

encode

public byte[] encode(byte[] pArray)

Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.

Specified by:

encode in interface BinaryEncoder

Parameters:

pArray - a byte array containing binary data

Returns:

A byte array containing only the base N alphabetic character data

encode

public byte[] encode(byte[] pArray,
 int offset,
 int length)

Encodes a byte[] containing binary data, into a byte[] containing characters in the alphabet.

Parameters:

pArray - a byte array containing binary data

offset - initial offset of the subarray.

length - length of the subarray.

Returns:

A byte array containing only the base N alphabetic character data

Since:

1.11

encode

public Object encode(Object obj)
              throws EncoderException

Encodes an Object using the Base-N algorithm. This method is provided in order to satisfy the requirements of the Encoder interface, and will throw an EncoderException if the supplied object is not of type byte[].

Specified by:

encode in interface Encoder

Parameters:

obj - Object to encode

Returns:

An object (of type byte[]) containing the Base-N encoded data which corresponds to the byte[] supplied.

Throws:

EncoderException - if the parameter supplied is not of type byte[]

encodeAsString

public String encodeAsString(byte[] pArray)

Encodes a byte[] containing binary data, into a String containing characters in the appropriate alphabet. Uses UTF8 encoding.

Parameters:

pArray - a byte array containing binary data

Returns:

String containing only character data in the appropriate alphabet.

Since:

1.5 This is a duplicate of encodeToString(byte[]); it was merged during refactoring.

encodeToString

public String encodeToString(byte[] pArray)

Encodes a byte[] containing binary data, into a String containing characters in the Base-N alphabet. Uses UTF8 encoding.

Parameters:

pArray - a byte array containing binary data

Returns:

A String containing only Base-N character data

ensureBufferSize

protected byte[] ensureBufferSize(int size,
 org.apache.commons.codec.binary.BaseNCodec.Context context)

Ensure that the buffer has room for size bytes

Parameters:

size - minimum spare space required

context - the context to be used

Returns:

the buffer

getCodecPolicy

public CodecPolicy getCodecPolicy()

Returns the decoding behavior policy.

The default is lenient. If the decoding policy is strict, then decoding will raise an IllegalArgumentException if trailing bits are not part of a valid encoding. Decoding will compose trailing bits into 8-bit bytes and discard the remainder.

Returns:

true if using strict decoding

Since:

1.15

getDefaultBufferSize

protected int getDefaultBufferSize()

Gets the default buffer size. Can be overridden.

Returns:

the default buffer size.

getEncodedLength

public long getEncodedLength(byte[] pArray)

Calculates the amount of space needed to encode the supplied array.

Parameters:

pArray - byte[] array which will later be encoded

Returns:

amount of space needed to encode the supplied array. Returns a long since a max-len array will require > Integer.MAX_VALUE

isInAlphabet

protected abstract boolean isInAlphabet(byte value)

Returns whether or not the octet is in the current alphabet. Does not allow whitespace or pad.

Parameters:

value - The value to test

Returns:

true if the value is defined in the current alphabet, false otherwise.

isInAlphabet

public boolean isInAlphabet(byte[] arrayOctet,
 boolean allowWSPad)

Tests a given byte array to see if it contains only valid characters within the alphabet. The method optionally treats whitespace and pad as valid.

Parameters:

arrayOctet - byte array to test

allowWSPad - if true, then whitespace and PAD are also allowed

Returns:

true if all bytes are valid characters in the alphabet or if the byte array is empty; false, otherwise

isInAlphabet

public boolean isInAlphabet(String basen)

Tests a given String to see if it contains only valid characters within the alphabet. The method treats whitespace and PAD as valid.

Parameters:

basen - String to test

Returns:

true if all characters in the String are valid characters in the alphabet or if the String is empty; false, otherwise

See Also:

• isInAlphabet(byte[], boolean)

isStrictDecoding

public boolean isStrictDecoding()

Returns true if decoding behavior is strict. Decoding will raise an IllegalArgumentException if trailing bits are not part of a valid encoding.

The default is false for lenient decoding. Decoding will compose trailing bits into 8-bit bytes and discard the remainder.

Returns:

true if using strict decoding

Since:

1.15