Package org.codehaus.stax2.typed

Class Base64Variant

java.lang.Object
org.codehaus.stax2.typed.Base64Variant
public final class Base64Variant extends Object
This abstract base class is used to define specific details of which variant of Base64 encoding/decoding is to be used. Although there is somewhat standard basic version (so-called "MIME Base64"), other variants exists, see Base64 Wikipedia entry for details.

Implementation notes:

  • The main complication here is trying to limit access to the underlying efficient encoding/decoding tables -- they are needed for fast operation, but it is potentially risky to expose raw arrays since they can not be protected against modification. The approach here is to try to limit access essentially to the main base64 codec classes; but this leads to bit awkward class structure
Since:
3.0.0

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    private final int[]
    _asciiToBase64
    Decoding table used for base 64 decoding.
    private final byte[]
    _base64ToAsciiB
    Alternative encoding table used for base 64 decoding when output is done as ascii bytes.
    private final char[]
    _base64ToAsciiC
    Encoding table used for base 64 decoding when output is done as characters.
    (package private) final int
    _maxLineLength
    Maximum number of encoded base64 characters to output during encoding before adding a linefeed, if line length is to be limited (Integer.MAX_VALUE if not limited).
    (package private) final String
    _name
    Symbolic name of variant; used for diagnostics/debugging.
    (package private) final char
    _paddingChar
    Characted used for padding, if any (PADDING_CHAR_NONE if not).
    (package private) final boolean
    _usesPadding
    Whether this variant uses padding or not.
    static final int
    BASE64_VALUE_INVALID
    Marker used to denote ascii characters that do not correspond to a 6-bit value (in this variant), and is not used as a padding character.
    static final int
    BASE64_VALUE_PADDING
    Marker used to denote ascii character (in decoding table) that is the padding character using this variant (if any).
    (package private) static final char
    PADDING_CHAR_NONE
    Placeholder used by "no padding" variant, to be used when a character value is needed.

  • Constructor Summary

    Constructors
    Constructor
    Description
    Base64Variant(String name, String base64Alphabet, boolean usesPadding, char paddingChar, int maxLineLength)
     
    Base64Variant(Base64Variant base, String name, boolean usesPadding, char paddingChar, int maxLineLength)
    "Copy constructor" that can be used when the base alphabet is identical to one used by another variant, but other details (padding, maximum line length) differ
    Base64Variant(Base64Variant base, String name, int maxLineLength)
    "Copy constructor" that can be used when the base alphabet is identical to one used by another variant except for the maximum line length (and obviously, name).

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    decodeBase64Byte(byte b)
     
    int
    decodeBase64Char(char c)
     
    byte
    encodeBase64BitsAsByte(int value)
     
    char
    encodeBase64BitsAsChar(int value)
     
    int
    encodeBase64Chunk(int b24, byte[] buffer, int ptr)
    Method that encodes given right-aligned (LSB) 24-bit value into 4 base64 bytes (ascii), stored in given result buffer.
    int
    encodeBase64Chunk(int b24, char[] buffer, int ptr)
    Method that encodes given right-aligned (LSB) 24-bit value into 4 base64 characters, stored in given result buffer.
    int
    encodeBase64Partial(int bits, int outputBytes, byte[] buffer, int outPtr)
    Method that outputs partial chunk (which only encodes one or two bytes of data).
    int
    encodeBase64Partial(int bits, int outputBytes, char[] buffer, int outPtr)
    Method that outputs partial chunk (which only encodes one or two bytes of data).
    int
    getMaxLineLength()
     
    String
    getName()
     
    byte
    getPaddingByte()
     
    char
    getPaddingChar()
     
    String
    toString()
     
    boolean
    usesPadding()
     
    boolean
    usesPaddingChar(char c)
     

    Methods inherited from class java.lang.Object

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

  • Field Details

    • PADDING_CHAR_NONE

      static final char PADDING_CHAR_NONE
      Placeholder used by "no padding" variant, to be used when a character value is needed.
      See Also:

    • BASE64_VALUE_INVALID

      public static final int BASE64_VALUE_INVALID
      Marker used to denote ascii characters that do not correspond to a 6-bit value (in this variant), and is not used as a padding character.
      See Also:

    • BASE64_VALUE_PADDING

      public static final int BASE64_VALUE_PADDING
      Marker used to denote ascii character (in decoding table) that is the padding character using this variant (if any).
      See Also:

    • _asciiToBase64

      private final int[] _asciiToBase64
      Decoding table used for base 64 decoding.

    • _base64ToAsciiC

      private final char[] _base64ToAsciiC
      Encoding table used for base 64 decoding when output is done as characters.

    • _base64ToAsciiB

      private final byte[] _base64ToAsciiB
      Alternative encoding table used for base 64 decoding when output is done as ascii bytes.

    • _name

      final String _name
      Symbolic name of variant; used for diagnostics/debugging.

    • _usesPadding

      final boolean _usesPadding
      Whether this variant uses padding or not.

    • _paddingChar

      final char _paddingChar
      Characted used for padding, if any (PADDING_CHAR_NONE if not).

    • _maxLineLength

      final int _maxLineLength
      Maximum number of encoded base64 characters to output during encoding before adding a linefeed, if line length is to be limited (Integer.MAX_VALUE if not limited).

      Note: for some output modes (when writing attributes) linefeeds may need to be avoided, and this value ignored.

  • Constructor Details

    • Base64Variant

      public Base64Variant(String name, String base64Alphabet, boolean usesPadding, char paddingChar, int maxLineLength)

    • Base64Variant

      public Base64Variant(Base64Variant base, String name, int maxLineLength)
      "Copy constructor" that can be used when the base alphabet is identical to one used by another variant except for the maximum line length (and obviously, name).

    • Base64Variant

      public Base64Variant(Base64Variant base, String name, boolean usesPadding, char paddingChar, int maxLineLength)
      "Copy constructor" that can be used when the base alphabet is identical to one used by another variant, but other details (padding, maximum line length) differ

  • Method Details

    • getName

      public String getName()

    • usesPadding

      public boolean usesPadding()

    • usesPaddingChar

      public boolean usesPaddingChar(char c)

    • getPaddingChar

      public char getPaddingChar()

    • getPaddingByte

      public byte getPaddingByte()

    • getMaxLineLength

      public int getMaxLineLength()

    • decodeBase64Char

      public int decodeBase64Char(char c)
      Returns:
      6-bit decoded value, if valid character;

    • decodeBase64Byte

      public int decodeBase64Byte(byte b)

    • encodeBase64BitsAsChar

      public char encodeBase64BitsAsChar(int value)

    • encodeBase64Chunk

      public int encodeBase64Chunk(int b24, char[] buffer, int ptr)
      Method that encodes given right-aligned (LSB) 24-bit value into 4 base64 characters, stored in given result buffer.

    • encodeBase64Partial

      public int encodeBase64Partial(int bits, int outputBytes, char[] buffer, int outPtr)
      Method that outputs partial chunk (which only encodes one or two bytes of data). Data given is still aligned same as if it as full data; that is, missing data is at the "right end" (LSB) of int.
      Parameters:
      outputBytes - Number of encoded bytes included (either 1 or 2)

    • encodeBase64BitsAsByte

      public byte encodeBase64BitsAsByte(int value)

    • encodeBase64Chunk

      public int encodeBase64Chunk(int b24, byte[] buffer, int ptr)
      Method that encodes given right-aligned (LSB) 24-bit value into 4 base64 bytes (ascii), stored in given result buffer.

    • encodeBase64Partial

      public int encodeBase64Partial(int bits, int outputBytes, byte[] buffer, int outPtr)
      Method that outputs partial chunk (which only encodes one or two bytes of data). Data given is still aligned same as if it as full data; that is, missing data is at the "right end" (LSB) of int.
      Parameters:
      outputBytes - Number of encoded bytes included (either 1 or 2)

    • toString

      public String toString()
      Overrides:
      toString in class Object