com.google.common.base

Class Utf8

java.lang.Object

com.google.common.base.Utf8

@Beta
 @GwtCompatible(emulated=true)
public final class Utf8
extends Object

Low-level, high-performance utility methods related to the UTF-8 character encoding. UTF-8 is defined in section D92 of The Unicode Standard Core Specification, Chapter 3.

The variant of UTF-8 implemented by this class is the restricted definition of UTF-8 introduced in Unicode 3.1. One implication of this is that it rejects "non-shortest form" byte sequences, even though the JDK decoder may accept them.

Since:

16.0

Author:

Martin Buchholz, Clément Roux

Method Summary

Modifier and Type	Method and Description
static int	encodedLength(CharSequence sequence) Returns the number of bytes in the UTF-8-encoded form of sequence.
static boolean	isWellFormed(byte[] bytes) Returns true if bytes is a well-formed UTF-8 byte sequence according to Unicode 6.0.
static boolean	isWellFormed(byte[] bytes, int off, int len) Returns whether the given byte array slice is a well-formed UTF-8 byte sequence, as defined by isWellFormed(byte[]).

Methods inherited from class java.lang.Object

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

Method Detail

encodedLength

public static int encodedLength(CharSequence sequence)

Returns the number of bytes in the UTF-8-encoded form of sequence. For a string, this method is equivalent to string.getBytes(UTF_8).length, but is more efficient in both time and space.

Throws:

IllegalArgumentException - if sequence contains ill-formed UTF-16 (unpaired surrogates)

isWellFormed

public static boolean isWellFormed(byte[] bytes)

Returns true if bytes is a well-formed UTF-8 byte sequence according to Unicode 6.0. Note that this is a stronger criterion than simply whether the bytes can be decoded. For example, some versions of the JDK decoder will accept "non-shortest form" byte sequences, but encoding never reproduces these. Such byte sequences are not considered well-formed.

This method returns true if and only if Arrays.equals(bytes, new String(bytes, UTF_8).getBytes(UTF_8)) does, but is more efficient in both time and space.

isWellFormed

public static boolean isWellFormed(byte[] bytes,
                                   int off,
                                   int len)

Returns whether the given byte array slice is a well-formed UTF-8 byte sequence, as defined by isWellFormed(byte[]). Note that this can be false even when isWellFormed(bytes) is true.

Parameters:

bytes - the input buffer

off - the offset in the buffer of the first byte to read

len - the number of bytes to read from the buffer