Base64 (Apache Tomcat 10.1.20 API Documentation)
Description: declaration: package: org.apache.tomcat.util.codec.binary, class: Base64

Package org.apache.tomcat.util.codec.binary

# Class Base64

java.lang.Object
org.apache.tomcat.util.codec.binary.BaseNCodec
org.apache.tomcat.util.codec.binary.Base64

public class Base64 extends BaseNCodec
Provides Base64 encoding and decoding as defined by RFC 2045.

This class implements section 6.8. Base64 Content-Transfer-Encoding from RFC 2045 Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies by Freed and Borenstein.

The class can be parameterized in the following manner with various constructors:

- URL-safe mode: Default off.
- Line length: Default 76. Line length that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.
- Line separator: Default is CRLF ("\r\n")

The URL-safe parameter is only applied to encode operations. Decoding seamlessly handles both modes.

Since this class operates directly on byte streams, and not character streams, it is hard-coded to only encode/decode character encodings which are compatible with the lower 127 ASCII chart (ISO-8859-1, Windows-1252, UTF-8, etc).

This class is thread-safe.

Since:
  1.0
See Also:
  - RFC 2045

- ## Field Summary

  ### Fields inherited from class org.apache.tomcat.util.codec.binary.BaseNCodec

  `lineLength, MASK_8BITS, MIME_CHUNK_SIZE, pad, PAD_DEFAULT, sm`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `Base64()`
  Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
  `Base64(boolean urlSafe)`
  Creates a Base64 codec used for decoding (all modes) and encoding in the given URL-safe mode.
  `Base64(int lineLength)`
  Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
  `Base64(int lineLength, byte[] lineSeparator)`
  Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.
  `Base64(int lineLength, byte[] lineSeparator, boolean urlSafe)`
  Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static byte[]`
  `decodeBase64(byte[] base64Data, int off, int len)`
  `static byte[]`
  `decodeBase64(String base64String)`
  Decodes a Base64 String into octets.
  `static byte[]`
  `decodeBase64URLSafe(String base64String)`
  `static byte[]`
  `encodeBase64(byte[] binaryData, boolean isChunked)`
  Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
  `static byte[]`
  `encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe)`
  Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
  `static byte[]`
  `encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe, int maxResultSize)`
  Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
  `static String`
  `encodeBase64String(byte[] binaryData)`
  Encodes binary data using the base64 algorithm but does not chunk the output.
  `static String`
  `encodeBase64URLSafeString(byte[] binaryData)`
  Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output.
  `protected boolean`
  `isInAlphabet(byte octet)`
  Returns whether or not the `octet` is in the Base64 alphabet.
  `static boolean`
  `isInAlphabet(char c)`
  `boolean`
  `isUrlSafe()`
  Returns our current encode mode.

  ### Methods inherited from class org.apache.tomcat.util.codec.binary.BaseNCodec

  `containsAlphabetOrPad, decode, decode, decode, encode, encode, encodeAsString, ensureBufferSize, getDefaultBufferSize, getEncodedLength`

  ### Methods inherited from class java.lang.Object

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

- ## Constructor Details

  - ### Base64

    public Base64()
    Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

    When encoding the line length is 0 (no chunking), and the encoding table is STANDARD_ENCODE_TABLE.

    When decoding all variants are supported.

  - ### Base64

    public Base64(boolean urlSafe)
    Creates a Base64 codec used for decoding (all modes) and encoding in the given URL-safe mode.

    When encoding the line length is 76, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.

    When decoding all variants are supported.

    Parameters:
      `urlSafe` - if `true`, URL-safe encoding is used. In most cases this should be set to `false`.
    Since:
      1.4

  - ### Base64

    public Base64(int lineLength)
    Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

    When encoding the line length is given in the constructor, the line separator is CRLF, and the encoding table is STANDARD_ENCODE_TABLE.

    Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.

    When decoding all variants are supported.

    Parameters:
      `lineLength` - Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
    Since:
      1.4

  - ### Base64

    public Base64(int lineLength, byte[] lineSeparator)
    Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

    When encoding the line length and line separator are given in the constructor, and the encoding table is STANDARD_ENCODE_TABLE.

    Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.

    When decoding all variants are supported.

    Parameters:
      `lineLength` - Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
      `lineSeparator` - Each line of encoded data will end with this sequence of bytes.
    Throws:
      `IllegalArgumentException` - Thrown when the provided lineSeparator included some base64 characters.
    Since:
      1.4

  - ### Base64

    public Base64(int lineLength, byte[] lineSeparator, boolean urlSafe)
    Creates a Base64 codec used for decoding (all modes) and encoding in URL-unsafe mode.

    When encoding the line length and line separator are given in the constructor, and the encoding table is STANDARD_ENCODE_TABLE.

    Line lengths that aren't multiples of 4 will still essentially end up being multiples of 4 in the encoded data.

    When decoding all variants are supported.

    Parameters:
      `lineLength` - Each line of encoded data will be at most of the given length (rounded down to the nearest multiple of 4). If lineLength <= 0, then the output will not be divided into lines (chunks). Ignored when decoding.
      `lineSeparator` - Each line of encoded data will end with this sequence of bytes.
      `urlSafe` - Instead of emitting '+' and '/' we emit '-' and '_' respectively. urlSafe is only applied to encode operations. Decoding seamlessly handles both modes. Note: no padding is added when using the URL-safe alphabet.
    Throws:
      `IllegalArgumentException` - Thrown when the `lineSeparator` contains Base64 characters.
    Since:
      1.4

- ## Method Details

  - ### decodeBase64

    public static byte[] decodeBase64(byte[] base64Data, int off, int len)

  - ### decodeBase64

    public static byte[] decodeBase64(String base64String)
    Decodes a Base64 String into octets.

    Note: this method seamlessly handles data encoded in URL-safe or normal mode.

    Parameters:
      `base64String` - String containing Base64 data
    Returns:
      Array containing decoded data.
    Since:
      1.4

  - ### decodeBase64URLSafe

    public static byte[] decodeBase64URLSafe(String base64String)

  - ### encodeBase64

    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked)
    Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
    Parameters:
      `binaryData` - Array containing binary data to encode.
      `isChunked` - if `true` this encoder will chunk the base64 output into 76 character blocks
    Returns:
      Base64-encoded data.
    Throws:
      `IllegalArgumentException` - Thrown when the input array needs an output array bigger than `Integer.MAX_VALUE`

  - ### encodeBase64

    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe)
    Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
    Parameters:
      `binaryData` - Array containing binary data to encode.
      `isChunked` - if `true` this encoder will chunk the base64 output into 76 character blocks
      `urlSafe` - if `true` this encoder will emit - and _ instead of the usual + and / characters. Note: no padding is added when encoding using the URL-safe alphabet.
    Returns:
      Base64-encoded data.
    Throws:
      `IllegalArgumentException` - Thrown when the input array needs an output array bigger than `Integer.MAX_VALUE`
    Since:
      1.4

  - ### encodeBase64

    public static byte[] encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe, int maxResultSize)
    Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
    Parameters:
      `binaryData` - Array containing binary data to encode.
      `isChunked` - if `true` this encoder will chunk the base64 output into 76 character blocks
      `urlSafe` - if `true` this encoder will emit - and _ instead of the usual + and / characters. Note: no padding is added when encoding using the URL-safe alphabet.
      `maxResultSize` - The maximum result size to accept.
    Returns:
      Base64-encoded data.
    Throws:
      `IllegalArgumentException` - Thrown when the input array needs an output array bigger than maxResultSize
    Since:
      1.4

  - ### encodeBase64String

    public static String encodeBase64String(byte[] binaryData)
    Encodes binary data using the base64 algorithm but does not chunk the output. NOTE: We changed the behavior of this method from multi-line chunking (commons-codec-1.4) to single-line non-chunking (commons-codec-1.5).
    Parameters:
      `binaryData` - binary data to encode
    Returns:
      String containing Base64 characters.
    Since:
      1.4 (NOTE: 1.4 chunked the output, whereas 1.5 does not).

  - ### encodeBase64URLSafeString

    public static String encodeBase64URLSafeString(byte[] binaryData)
    Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output. The url-safe variation emits - and _ instead of + and / characters. Note: no padding is added.
    Parameters:
      `binaryData` - binary data to encode
    Returns:
      String containing Base64 characters
    Since:
      1.4

  - ### isInAlphabet

    public static boolean isInAlphabet(char c)

  - ### isInAlphabet

    protected boolean isInAlphabet(byte octet)
    Returns whether or not the `octet` is in the Base64 alphabet.
    Specified by:
      `isInAlphabet` in class `BaseNCodec`
    Parameters:
      `octet` - The value to test
    Returns:
      `true` if the value is defined in the Base64 alphabet `false` otherwise.

  - ### isUrlSafe

    public boolean isUrlSafe()
    Returns our current encode mode. True if we're URL-SAFE, false otherwise.
    Returns:
      true if we're in URL-SAFE mode, false otherwise.
    Since:
      1.4