info.monitorenter.cpdetector.io

类 ByteOrderMarkDetector

java.lang.Object

info.monitorenter.cpdetector.io.AbstractCodepageDetector

info.monitorenter.cpdetector.io.ByteOrderMarkDetector

所有已实现的接口:

ICodepageDetector, Serializable, Comparable

public class ByteOrderMarkDetector
extends AbstractCodepageDetector
implements ICodepageDetector

This detector identifies byte order marks of the following codepages to give a 100 % deterministic result in case of detection.

00 00 FE FF	UCS-4, big-endian machine (1234 order)
FF FE 00 00	UCS-4,little-endian machine (4321 order)
00 00 FF FE	UCS-4, unusual octet order (2143)
FE FF 00 00	UCS-4, unusual octet order (3412)
FE FF ## ##	UTF-16, big-endian
FF FE ## ##	UTF-16, little-endian
EF BB BF	UTF-8

Note that this detector is very fast as it only has to read a maximum of 8 bytes to provide a result. Nevertheless it is senseless to add it to the configuration if the documents to detect will have a low rate of documents in the codepages that will be detected. If added to the configuration of CodepageDetectorProxy it should be at front position to save computations of the following detection processses.

This implementation is based on:
W3C XML Specification 1.0 3rd Edition, F.1 Detection Without External Encoding Information .

This implementation does the same as UnicodeDetector but with a different read strategy (read each byte separately) and a switch case tree (-> bytecode tableswitch). Would be great to have a performance comparison. Maybe the read of 4 bytes in a row combined with the switch could make this implementation the winner.

版本:

$Revision: 1.3 $

作者:

Achim Westermann

另请参阅:

序列化表格

构造器概要

构造器

构造器和说明
ByteOrderMarkDetector()

方法概要

方法

限定符和类型	方法和说明
Charset	detectCodepage(InputStream in, int length) This method allows to detect the charset encoding from every source (even a String, which an URL does not decorate!).
Charset	detectCodepage(URL url) Delegates to detectCodepage(InputStream, int)with a buffered input stream of size 10 (8 needed as maximum).

从类继承的方法 info.monitorenter.cpdetector.io.AbstractCodepageDetector

compareTo, open

从类继承的方法 java.lang.Object

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

从接口继承的方法 info.monitorenter.cpdetector.io.ICodepageDetector

open

从接口继承的方法 java.lang.Comparable

compareTo

构造器详细资料

ByteOrderMarkDetector

public ByteOrderMarkDetector()

方法详细资料

detectCodepage

public Charset detectCodepage(InputStream in,
                     int length)
                       throws IOException

从接口复制的说明: ICodepageDetector

This method allows to detect the charset encoding from every source (even a String, which an URL does not decorate!).

Note that you cannot reuse the given InputStream unless it supports marking (InputStream.markSupported() == true), you mark the initial position with a sufficient readlimit and invoke reset afterwards (without getting any exception).

指定者:

detectCodepage 在接口中 ICodepageDetector

参数:

in - An InputStream for the document, that supports mark and a readlimit of argument length.

length - The amount of bytes to take into account. This number should not be longer than the amount of bytes retrievable from the InputStream but should be as long as possible to give the fallback detection (chardet) more hints to guess.

抛出:

IOException

另请参阅:

ICodepageDetector.detectCodepage(InputStream, int)

detectCodepage

public Charset detectCodepage(URL url)
                       throws IOException

Delegates to detectCodepage(InputStream, int)with a buffered input stream of size 10 (8 needed as maximum).

指定者:

detectCodepage 在接口中 ICodepageDetector

覆盖:

detectCodepage 在类中 AbstractCodepageDetector

返回:

null, if the codepage of the document specified by the given URL was not detected or the Charsetthat represents the document's codepage.

抛出:

IOException - thrown to indicate that it is was not possible to open the document specified by the given URL.

另请参阅:

ICodepageDetector.detectCodepage(URL)