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International Component for Unicode for Java (ICU4J) is a mature, widely used Java library
providing Unicode and Globalization support
/**
*******************************************************************************
* Copyright (C) 2005-2012, International Business Machines Corporation and *
* others. All Rights Reserved. *
*******************************************************************************
*/
package com.ibm.icu.text;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
/**
* This class represents a charset that has been identified by a CharsetDetector
* as a possible encoding for a set of input data. From an instance of this
* class, you can ask for a confidence level in the charset identification,
* or for Java Reader or String to access the original byte data in Unicode form.
*
* Instances of this class are created only by CharsetDetectors.
*
* Note: this class has a natural ordering that is inconsistent with equals.
* The natural ordering is based on the match confidence value.
*
* @stable ICU 3.4
*/
public class CharsetMatch implements Comparable {
/**
* Create a java.io.Reader for reading the Unicode character data corresponding
* to the original byte data supplied to the Charset detect operation.
*
* CAUTION: if the source of the byte data was an InputStream, a Reader
* can be created for only one matching char set using this method. If more
* than one charset needs to be tried, the caller will need to reset
* the InputStream and create InputStreamReaders itself, based on the charset name.
*
* @return the Reader for the Unicode character data.
*
* @stable ICU 3.4
*/
public Reader getReader() {
InputStream inputStream = fInputStream;
if (inputStream == null) {
inputStream = new ByteArrayInputStream(fRawInput, 0, fRawLength);
}
try {
inputStream.reset();
return new InputStreamReader(inputStream, getName());
} catch (IOException e) {
return null;
}
}
/**
* Create a Java String from Unicode character data corresponding
* to the original byte data supplied to the Charset detect operation.
*
* @return a String created from the converted input data.
*
* @stable ICU 3.4
*/
public String getString() throws java.io.IOException {
return getString(-1);
}
/**
* Create a Java String from Unicode character data corresponding
* to the original byte data supplied to the Charset detect operation.
* The length of the returned string is limited to the specified size;
* the string will be trunctated to this length if necessary. A limit value of
* zero or less is ignored, and treated as no limit.
*
* @param maxLength The maximium length of the String to be created when the
* source of the data is an input stream, or -1 for
* unlimited length.
* @return a String created from the converted input data.
*
* @stable ICU 3.4
*/
public String getString(int maxLength) throws java.io.IOException {
String result = null;
if (fInputStream != null) {
StringBuilder sb = new StringBuilder();
char[] buffer = new char[1024];
Reader reader = getReader();
int max = maxLength < 0? Integer.MAX_VALUE : maxLength;
int bytesRead = 0;
while ((bytesRead = reader.read(buffer, 0, Math.min(max, 1024))) >= 0) {
sb.append(buffer, 0, bytesRead);
max -= bytesRead;
}
reader.close();
return sb.toString();
} else {
String name = getName();
/*
* getName() may return a name with a suffix 'rtl' or 'ltr'. This cannot
* be used to open a charset (e.g. IBM424_rtl). The ending '_rtl' or 'ltr'
* should be stripped off before creating the string.
*/
int startSuffix = name.indexOf("_rtl") < 0 ? name.indexOf("_ltr") : name.indexOf("_rtl");
if (startSuffix > 0) {
name = name.substring(0, startSuffix);
}
result = new String(fRawInput, name);
}
return result;
}
/**
* Get an indication of the confidence in the charset detected.
* Confidence values range from 0-100, with larger numbers indicating
* a better match of the input data to the characteristics of the
* charset.
*
* @return the confidence in the charset match
*
* @stable ICU 3.4
*/
public int getConfidence() {
return fConfidence;
}
/**
* Get the name of the detected charset.
* The name will be one that can be used with other APIs on the
* platform that accept charset names. It is the "Canonical name"
* as defined by the class java.nio.charset.Charset; for
* charsets that are registered with the IANA charset registry,
* this is the MIME-preferred registerd name.
*
* @see java.nio.charset.Charset
* @see java.io.InputStreamReader
*
* @return The name of the charset.
*
* @stable ICU 3.4
*/
public String getName() {
return fCharsetName;
}
/**
* Get the ISO code for the language of the detected charset.
*
* @return The ISO code for the language or null if the language cannot be determined.
*
* @stable ICU 3.4
*/
public String getLanguage() {
return fLang;
}
/**
* Compare to other CharsetMatch objects.
* Comparison is based on the match confidence value, which
* allows CharsetDetector.detectAll() to order its results.
*
* @param other the CharsetMatch object to compare against.
* @return a negative integer, zero, or a positive integer as the
* confidence level of this CharsetMatch
* is less than, equal to, or greater than that of
* the argument.
* @throws ClassCastException if the argument is not a CharsetMatch.
* @stable ICU 4.4
*/
public int compareTo (CharsetMatch other) {
int compareResult = 0;
if (this.fConfidence > other.fConfidence) {
compareResult = 1;
} else if (this.fConfidence < other.fConfidence) {
compareResult = -1;
}
return compareResult;
}
/*
* Constructor. Implementation internal
*/
CharsetMatch(CharsetDetector det, CharsetRecognizer rec, int conf) {
fConfidence = conf;
// The references to the original application input data must be copied out
// of the charset recognizer to here, in case the application resets the
// recognizer before using this CharsetMatch.
if (det.fInputStream == null) {
// We only want the existing input byte data if it came straight from the user,
// not if is just the head of a stream.
fRawInput = det.fRawInput;
fRawLength = det.fRawLength;
}
fInputStream = det.fInputStream;
fCharsetName = rec.getName();
fLang = rec.getLanguage();
}
/*
* Constructor. Implementation internal
*/
CharsetMatch(CharsetDetector det, CharsetRecognizer rec, int conf, String csName, String lang) {
fConfidence = conf;
// The references to the original application input data must be copied out
// of the charset recognizer to here, in case the application resets the
// recognizer before using this CharsetMatch.
if (det.fInputStream == null) {
// We only want the existing input byte data if it came straight from the user,
// not if is just the head of a stream.
fRawInput = det.fRawInput;
fRawLength = det.fRawLength;
}
fInputStream = det.fInputStream;
fCharsetName = csName;
fLang = lang;
}
//
// Private Data
//
private int fConfidence;
private byte[] fRawInput = null; // Original, untouched input bytes.
// If user gave us a byte array, this is it.
private int fRawLength; // Length of data in fRawInput array.
private InputStream fInputStream = null; // User's input stream, or null if the user
// gave us a byte array.
private String fCharsetName; // The name of the charset this CharsetMatch
// represents. Filled in by the recognizer.
private String fLang; // The language, if one was determined by
// the recognizer during the detect operation.
}