com.weibo.breeze

类 Utf8

java.lang.Object

com.weibo.breeze.Utf8

public class Utf8
extends Object

A set of low-level, high-performance static utility methods related to the UTF-8 character encoding. This class has no dependencies outside of the core JDK libraries.

There are several variants of UTF-8. The one implemented by this class is the restricted definition of UTF-8 introduced in Unicode 3.1, which mandates the rejection of "overlong" byte sequences as well as rejection of 3-byte surrogate codepoint byte sequences. Note that the UTF-8 decoder included in Oracle's JDK has been modified to also reject "overlong" byte sequences, but (as of 2011) still accepts 3-byte surrogate codepoint byte sequences.

The byte sequences considered valid by this class are exactly those that can be roundtrip converted to Strings and back to bytes using the UTF-8 charset, without loss:

 
 Arrays.equals(bytes, new String(bytes, Internal.UTF_8).getBytes(Internal.UTF_8))
 

See the Unicode Standard,
Table 3-6. UTF-8 Bit Distribution,
Table 3-7. Well Formed UTF-8 Byte Sequences.

This class supports decoding of partial byte sequences, so that the bytes in a complete UTF-8 byte sequences can be stored in multiple segments. Methods typically return MALFORMED if the partial byte sequence is definitely not well-formed, COMPLETE if it is well-formed in the absence of additional input, or if the byte sequence apparently terminated in the middle of a character, an opaque integer "state" value containing enough information to decode the character when passed to a subsequent invocation of a partial decoding method.

作者:

martinrb@google.com (Martin Buchholz)

字段概要

字段

限定符和类型	字段和说明
static int	COMPLETE State value indicating that the byte sequence is well-formed and complete (no further bytes are needed to complete a character).
static int	MALFORMED State value indicating that the byte sequence is definitely not well-formed.

构造器概要

构造器

构造器和说明
Utf8()

方法概要

限定符和类型	方法和说明
static boolean	isValidUtf8(byte[] bytes) Returns true if the given byte array is a well-formed UTF-8 byte sequence.
static boolean	isValidUtf8(byte[] bytes, int index, int limit) Returns true if the given byte array slice is a well-formed UTF-8 byte sequence.
static int	partialIsValidUtf8(int state, byte[] bytes, int index, int limit) Tells whether the given byte array slice is a well-formed, malformed, or incomplete UTF-8 byte sequence.

从类继承的方法 java.lang.Object

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

字段详细资料

COMPLETE

public static final int COMPLETE

State value indicating that the byte sequence is well-formed and complete (no further bytes are needed to complete a character).

另请参阅:

常量字段值

MALFORMED

public static final int MALFORMED

State value indicating that the byte sequence is definitely not well-formed.

另请参阅:

常量字段值

构造器详细资料

Utf8

public Utf8()

方法详细资料

isValidUtf8

public static boolean isValidUtf8(byte[] bytes)

Returns true if the given byte array is a well-formed UTF-8 byte sequence.

This is a convenience method, equivalent to a call to isValidUtf8(bytes, 0, bytes.length).

isValidUtf8

public static boolean isValidUtf8(byte[] bytes,
                                  int index,
                                  int limit)

Returns true if the given byte array slice is a well-formed UTF-8 byte sequence. The range of bytes to be checked extends from index index, inclusive, to limit, exclusive.

This is a convenience method, equivalent to partialIsValidUtf8(bytes, index, limit) == Utf8.COMPLETE.

partialIsValidUtf8

public static int partialIsValidUtf8(int state,
                                     byte[] bytes,
                                     int index,
                                     int limit)

Tells whether the given byte array slice is a well-formed, malformed, or incomplete UTF-8 byte sequence. The range of bytes to be checked extends from index index, inclusive, to limit, exclusive.

参数:

state - either COMPLETE (if this is the initial decoding operation) or the value returned from a call to a partial decoding method for the previous bytes

返回:

MALFORMED if the partial byte sequence is definitely not well-formed, COMPLETE if it is well-formed (no additional input needed), or if the byte sequence is "incomplete", i.e. apparently terminated in the middle of a character, an opaque integer "state" value containing enough information to decode the character when passed to a subsequent invocation of a partial decoding method.