com.diffplug.common.base

Class Utf8

java.lang.Object

com.diffplug.common.base.Utf8

@Beta
 @GwtCompatible
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

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

@CheckReturnValue
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

@CheckReturnValue
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

@CheckReturnValue
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