Package com.mindprod.base64

Class Base64

java.lang.Object
com.mindprod.base64.Base64
public class Base64 extends Object
Encode arbitrary binary into printable ASCII using BASE64 encoding.

Base64 is a way of encoding 8-bit characters using only ASCII printable characters similar to UUENCODE. UUENCODE includes a filename where BASE64 does not. The spec is described in RFC 2045. Base64 is a scheme where 3 bytes are concatenated, then split to form 4 groups of 6-bits each; and each 6-bits gets translated to an encoded printable ASCII character, via a table lookup. An encoded string is therefore longer than the original by about 1/3. The "=" character is used to pad the end. Base64 is used, among other things, to encode the user:password string in an Authorization: header for HTTP. Don't confuse Base64 with x-www-form-urlencoded which is handled by Java.net.URLEncoder.encode/decode

If you don't like this code, there is another implementation at http://www.ruffboy.com/download.htm Sun has an undocumented method called sun.misc.Base64Encoder.encode. You could use hex, simpler to code, but not as compact.

If you wanted to encode a giant file, you could do it in large chunks that are even multiples of 3 bytes, except for the last chunk, and append the outputs.

To encode a string, rather than binary data java.net.URLEncoder may be better. See printable characters in the Java glossary for a discussion of the differences.

Base 64 armouring uses only the characters A-Z a-z 0-9 +/=. This makes it suitable for encoding binary data as SQL strings, that will work no matter what the encoding. Unfortunately + / and = all have special meaning in URLs.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final boolean
    DEBUGGING
    used to disable test driver

  • Constructor Summary

    Constructors
    Constructor
    Description
    Base64()
    constructor

  • Method Summary

    Modifier and Type
    Method
    Description
    byte[]
    decode(String s)
    decode a well-formed complete Base64 string back into an array of bytes.
    static void
    display(byte[] b)
    debug display array as if there were 8-bit Latin-1
    String
    encode(byte[] b)
    Encode an arbitrary array of bytes as Base64 printable ASCII.
    static void
    main(String[] args)
    test driver
    void
    setLineLength(int length)
    determines how long the lines are that are generated by encode.
    void
    setLineSeparator(String lineSeparator)
    How lines are separated.
    static void
    show(byte[] b)
    debug display array as hex

    Methods inherited from class java.lang.Object

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

  • Field Details

    • DEBUGGING

      public static final boolean DEBUGGING
      used to disable test driver
      See Also:

  • Constructor Details

    • Base64

      public Base64()
      constructor

  • Method Details

    • display

      public static void display(byte[] b)
      debug display array as if there were 8-bit Latin-1
      Parameters:
      b - byte array to display

    • show

      public static void show(byte[] b)
      debug display array as hex
      Parameters:
      b - byte array to display

    • setLineSeparator

      public void setLineSeparator(String lineSeparator)
      How lines are separated. Ignored by decode.
      Parameters:
      lineSeparator - may be "" but not null. Usually contains only a combination of chars \n and \r. Could be any chars not in set A-Z a-z 0-9 + /.

    • decode

      public byte[] decode(String s)
      decode a well-formed complete Base64 string back into an array of bytes. It must have an even multiple of 4 data characters (not counting \n), padded out with = as needed.
      Parameters:
      s - base64-encoded string
      Returns:
      plaintext as a byte array.

    • encode

      public String encode(byte[] b)
      Encode an arbitrary array of bytes as Base64 printable ASCII. It will be broken into lines of 72 chars each. The last line is not terminated with a line separator. The output will always have an even multiple of data characters, exclusive of \n. It is padded out with =.
      Parameters:
      b - byte array to encode, typically produced by a ByteArrayOutputStream
      Returns:
      base-64 encoded String, not char[] or byte[].

    • setLineLength

      public void setLineLength(int length)
      determines how long the lines are that are generated by encode. Ignored by decode.
      Parameters:
      length - 0 means no newlines inserted. Must be a multiple of 4.

    • main

      public static void main(String[] args)
      test driver
      Parameters:
      args - not used