Class BaseEncoding

java.lang.Object
com.google.common.io.BaseEncoding
@GwtCompatible public abstract class BaseEncoding extends 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(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

  • Method Details

    • encode

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

    • encode

      public final 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 OutputStream encodingStream(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.

    • encodingSink

      @GwtIncompatible public final ByteSink encodingSink(CharSink encodedSink)
      Returns a ByteSink that writes base-encoded bytes to the specified CharSink.

    • canDecode

      public abstract boolean canDecode(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(CharSequence chars)
      Decodes the specified character sequence, and returns the resulting byte[]. This is the inverse operation to encode(byte[]).
      Throws:
      IllegalArgumentException - if the input is not a valid encoded string according to this encoding.

    • decodingStream

      @GwtIncompatible public abstract InputStream decodingStream(Reader reader)
      Returns an InputStream that decodes base-encoded input from the specified Reader. The returned stream throws a BaseEncoding.DecodingException upon decoding-specific errors.

    • decodingSource

      @GwtIncompatible public final ByteSource decodingSource(CharSource encodedSource)
      Returns a ByteSource that reads base-encoded bytes from the specified CharSource.

    • 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:
      IllegalArgumentException - if this padding character is already used in the alphabet or a separator

    • withSeparator

      public abstract BaseEncoding withSeparator(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:
      IllegalArgumentException - if any alphabet or padding characters appear in the separator string, or if n <= 0
      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:
      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:
      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:
      IllegalStateException - if the alphabet used by this encoding contains mixed upper- and lower-case characters
      Since:
      32.0.0

    • base64

      public static BaseEncoding base64()
      The "base64" base encoding specified by RFC 4648 section 4, Base 64 Encoding. (This is the same as the base 64 encoding from RFC 3548.)

      The character '=' is used for padding, but can be omitted or replaced.

      No line feeds are added by default, as per RFC 4648 section 3.1, Line Feeds in Encoded Data. Line feeds may be added using withSeparator(String, int).

    • base64Url

      public 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.)

      The character '=' is used for padding, but can be omitted or replaced.

      No line feeds are added by default, as per RFC 4648 section 3.1, Line Feeds in Encoded Data. Line feeds may be added using withSeparator(String, int).

    • base32

      public static BaseEncoding base32()
      The "base32" encoding specified by RFC 4648 section 6, Base 32 Encoding. (This is the same as the base 32 encoding from RFC 3548.)

      The character '=' is used for padding, but can be omitted or replaced.

      No line feeds are added by default, as per RFC 4648 section 3.1, Line Feeds in Encoded Data. Line feeds may be added using withSeparator(String, int).

    • base32Hex

      public static BaseEncoding base32Hex()
      The "base32hex" encoding specified by RFC 4648 section 7, Base 32 Encoding with Extended Hex Alphabet. There is no corresponding encoding in RFC 3548.

      The character '=' is used for padding, but can be omitted or replaced.

      No line feeds are added by default, as per RFC 4648 section 3.1, Line Feeds in Encoded Data. Line feeds may be added using withSeparator(String, int).

    • base16

      public static BaseEncoding base16()
      The "base16" encoding specified by RFC 4648 section 8, Base 16 Encoding. (This is the same as the base 16 encoding from RFC 3548.) This is commonly known as "hexadecimal" format.

      No padding is necessary in base 16, so withPadChar(char) and omitPadding() have no effect.

      No line feeds are added by default, as per RFC 4648 section 3.1, Line Feeds in Encoded Data. Line feeds may be added using withSeparator(String, int).