Class BaseEncoding


  • @GwtCompatible(emulated=true)
    public abstract class BaseEncoding
    extends java.lang.Object
    A binary encoding scheme for reversibly translating between byte sequences and printable ASCII strings. This class includes several constants for encoding schemes specified by RFC 4648. For example, the expression:
    
     BaseEncoding.base32().encode("foo".getBytes(Charsets.US_ASCII))
     

    returns the string "MZXW6===", and

    
     byte[] decoded = BaseEncoding.base32().decode("MZXW6===");
     

    ...returns the ASCII bytes of the string "foo".

    By default, BaseEncoding's behavior is relatively strict and in accordance with RFC 4648. Decoding rejects characters in the wrong case, though padding is optional. To modify encoding and decoding behavior, use configuration methods to obtain a new encoding with modified behavior:

    
     BaseEncoding.base16().lowerCase().decode("deadbeef");
     

    Warning: BaseEncoding instances are immutable. Invoking a configuration method has no effect on the receiving instance; you must store and use the new encoding instance it returns, instead.

    
     // Do NOT do this
     BaseEncoding hex = BaseEncoding.base16();
     hex.lowerCase(); // does nothing!
     return hex.decode("deadbeef"); // throws an IllegalArgumentException
     

    It is guaranteed that encoding.decode(encoding.encode(x)) is always equal to x, but the reverse does not necessarily hold.

    Encodings
    Encoding Alphabet char:byte ratio Default padding Comments
    base16() 0-9 A-F 2.00 N/A Traditional hexadecimal. Defaults to upper case.
    base32() A-Z 2-7 1.60 = Human-readable; no possibility of mixing up 0/O or 1/I. Defaults to upper case.
    base32Hex() 0-9 A-V 1.60 = "Numerical" base 32; extended from the traditional hex alphabet. Defaults to upper case.
    base64() A-Z a-z 0-9 + / 1.33 =
    base64Url() A-Z a-z 0-9 - _ 1.33 = Safe to use as filenames, or to pass in URLs without escaping

    All instances of this class are immutable, so they may be stored safely as static constants.

    Since:
    14.0
    Author:
    Louis Wasserman
    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  BaseEncoding.DecodingException
      Exception indicating invalid base-encoded input encountered while decoding.
    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      static BaseEncoding base16()
      The "base16" encoding specified by RFC 4648 section 8, Base 16 Encoding.
      static BaseEncoding base32()
      The "base32" encoding specified by RFC 4648 section 6, Base 32 Encoding.
      static BaseEncoding base32Hex()
      The "base32hex" encoding specified by RFC 4648 section 7, Base 32 Encoding with Extended Hex Alphabet.
      static BaseEncoding base64()
      The "base64" base encoding specified by RFC 4648 section 4, Base 64 Encoding.
      static BaseEncoding base64Url()
      The "base64url" encoding specified by RFC 4648 section 5, Base 64 Encoding with URL and Filename Safe Alphabet, also sometimes referred to as the "web safe Base64." (This is the same as the base 64 encoding with URL and filename safe alphabet from RFC 3548.)
      abstract boolean canDecode​(java.lang.CharSequence chars)
      Determines whether the specified character sequence is a valid encoded string according to this encoding.
      byte[] decode​(java.lang.CharSequence chars)
      Decodes the specified character sequence, and returns the resulting byte[].
      ByteSource decodingSource​(CharSource encodedSource)
      Returns a ByteSource that reads base-encoded bytes from the specified CharSource.
      abstract java.io.InputStream decodingStream​(java.io.Reader reader)
      Returns an InputStream that decodes base-encoded input from the specified Reader.
      java.lang.String encode​(byte[] bytes)
      Encodes the specified byte array, and returns the encoded String.
      java.lang.String encode​(byte[] bytes, int off, int len)
      Encodes the specified range of the specified byte array, and returns the encoded String.
      ByteSink encodingSink​(CharSink encodedSink)
      Returns a ByteSink that writes base-encoded bytes to the specified CharSink.
      abstract java.io.OutputStream encodingStream​(java.io.Writer writer)
      Returns an OutputStream that encodes bytes using this encoding into the specified Writer.
      abstract BaseEncoding ignoreCase()
      Returns an encoding that behaves equivalently to this encoding, but decodes letters without regard to case.
      abstract BaseEncoding lowerCase()
      Returns an encoding that behaves equivalently to this encoding, but encodes and decodes with lowercase letters.
      abstract BaseEncoding omitPadding()
      Returns an encoding that behaves equivalently to this encoding, but omits any padding characters as specified by RFC 4648 section 3.2, Padding of Encoded Data.
      abstract BaseEncoding upperCase()
      Returns an encoding that behaves equivalently to this encoding, but encodes and decodes with uppercase letters.
      abstract BaseEncoding withPadChar​(char padChar)
      Returns an encoding that behaves equivalently to this encoding, but uses an alternate character for padding.
      abstract BaseEncoding withSeparator​(java.lang.String separator, int n)
      Returns an encoding that behaves equivalently to this encoding, but adds a separator string after every n characters.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Method Detail

      • encode

        public java.lang.String encode​(byte[] bytes)
        Encodes the specified byte array, and returns the encoded String.
      • encode

        public final java.lang.String encode​(byte[] bytes,
                                             int off,
                                             int len)
        Encodes the specified range of the specified byte array, and returns the encoded String.
      • encodingStream

        @GwtIncompatible
        public abstract java.io.OutputStream encodingStream​(java.io.Writer writer)
        Returns an OutputStream that encodes bytes using this encoding into the specified Writer. When the returned OutputStream is closed, so is the backing Writer.
      • canDecode

        public abstract boolean canDecode​(java.lang.CharSequence chars)
        Determines whether the specified character sequence is a valid encoded string according to this encoding.
        Since:
        20.0
      • decode

        public final byte[] decode​(java.lang.CharSequence chars)
        Decodes the specified character sequence, and returns the resulting byte[]. This is the inverse operation to encode(byte[]).
        Throws:
        java.lang.IllegalArgumentException - if the input is not a valid encoded string according to this encoding.
      • omitPadding

        public abstract BaseEncoding omitPadding()
        Returns an encoding that behaves equivalently to this encoding, but omits any padding characters as specified by RFC 4648 section 3.2, Padding of Encoded Data.
      • withPadChar

        public abstract BaseEncoding withPadChar​(char padChar)
        Returns an encoding that behaves equivalently to this encoding, but uses an alternate character for padding.
        Throws:
        java.lang.IllegalArgumentException - if this padding character is already used in the alphabet or a separator
      • withSeparator

        public abstract BaseEncoding withSeparator​(java.lang.String separator,
                                                   int n)
        Returns an encoding that behaves equivalently to this encoding, but adds a separator string after every n characters. Any occurrences of any characters that occur in the separator are skipped over in decoding.
        Throws:
        java.lang.IllegalArgumentException - if any alphabet or padding characters appear in the separator string, or if n <= 0
        java.lang.UnsupportedOperationException - if this encoding already uses a separator
      • upperCase

        public abstract BaseEncoding upperCase()
        Returns an encoding that behaves equivalently to this encoding, but encodes and decodes with uppercase letters. Padding and separator characters remain in their original case.
        Throws:
        java.lang.IllegalStateException - if the alphabet used by this encoding contains mixed upper- and lower-case characters
      • lowerCase

        public abstract BaseEncoding lowerCase()
        Returns an encoding that behaves equivalently to this encoding, but encodes and decodes with lowercase letters. Padding and separator characters remain in their original case.
        Throws:
        java.lang.IllegalStateException - if the alphabet used by this encoding contains mixed upper- and lower-case characters
      • ignoreCase

        public abstract BaseEncoding ignoreCase()
        Returns an encoding that behaves equivalently to this encoding, but decodes letters without regard to case.
        Throws:
        java.lang.IllegalStateException - if the alphabet used by this encoding contains mixed upper- and lower-case characters