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57
58
59 package com.sun.org.apache.xml.internal.serialize;
60
61 import java.io.OutputStream JavaDoc;
62 import java.io.OutputStreamWriter JavaDoc;
63 import java.io.UnsupportedEncodingException JavaDoc;
64 import java.io.Writer JavaDoc;
65 import com.sun.org.apache.xerces.internal.util.EncodingMap;
66 import java.nio.charset.Charset JavaDoc;
67 import java.nio.charset.CharsetEncoder JavaDoc;
68 import java.nio.charset.UnsupportedCharsetException JavaDoc;
69 import java.nio.charset.IllegalCharsetNameException JavaDoc;
70 /**
71  * This class represents an encoding.
72  *
73  * @version $Id: EncodingInfo.java,v 1.2 2003/12/05 10:08:55 vk112360 Exp $
74  */
75 public class EncodingInfo {
76
77     // Method: sun.io.CharToByteConverter.getConverter(java.lang.String)
78 private static java.lang.reflect.Method JavaDoc fgGetConverterMethod = null;
79     
80     // Method: sun.io.CharToByteConverter.canConvert(char)
81 private static java.lang.reflect.Method JavaDoc fgCanConvertMethod = null;
82     
83     // Flag indicating whether or not sun.io.CharToByteConverter is available.
84 private static boolean fgConvertersAvailable = false;
85     
86     // An array to hold the argument for a method of CharToByteConverter.
87 private Object JavaDoc [] fArgsForMethod = null;
88     
89     // name of encoding as registered with IANA;
90 // preferably a MIME name, but aliases are fine too.
91 String JavaDoc ianaName;
92     String JavaDoc javaName;
93     int lastPrintable;
94     
95     // The charToByteConverter with which we test unusual characters.
96 Object JavaDoc fCharToByteConverter = null;
97     
98     // Is the converter null because it can't be instantiated
99 // for some reason (perhaps we're running with insufficient authority as
100 // an applet?
101 boolean fHaveTriedCToB = false;
102     Charset JavaDoc nioCharset = null;
103     CharsetEncoder JavaDoc nioCharEncoder = null;
104     /**
105      * Creates new <code>EncodingInfo</code> instance.
106      */
107     public EncodingInfo(String JavaDoc ianaName, String JavaDoc javaName, int lastPrintable) {
108         this.ianaName = ianaName;
109         this.javaName = EncodingMap.getIANA2JavaMapping(ianaName);
110         this.lastPrintable = lastPrintable;
111         try{
112              nioCharset = Charset.forName(this.javaName);
113              if(nioCharset.canEncode())
114                 nioCharEncoder = nioCharset.newEncoder();
115         }catch(IllegalCharsetNameException JavaDoc ie){
116             nioCharset = null;
117             nioCharEncoder = null;
118         }catch(UnsupportedCharsetException JavaDoc ue){
119             nioCharset = null;
120             nioCharEncoder = null;
121         }
122     }
123
124     /**
125      * Returns a MIME charset name of this encoding.
126      */
127     public String JavaDoc getIANAName() {
128         return this.ianaName;
129     }
130
131     /**
132      * Returns a writer for this encoding based on
133      * an output stream.
134      *
135      * @return A suitable writer
136      * @exception UnsupportedEncodingException There is no convertor
137      * to support this encoding
138      */
139     public Writer JavaDoc getWriter(OutputStream JavaDoc output)
140         throws UnsupportedEncodingException JavaDoc {
141         // this should always be true!
142 if (javaName != null)
143             return new OutputStreamWriter JavaDoc(output, javaName);
144         javaName = EncodingMap.getIANA2JavaMapping(ianaName);
145         if(javaName == null)
146             // use UTF-8 as preferred encoding
147 return new OutputStreamWriter JavaDoc(output, "UTF8");
148         return new OutputStreamWriter JavaDoc(output, javaName);
149     }
150     /**
151      * Checks whether the specified character is printable or not
152      * in this encoding.
153      *
154      * @param ch a code point (0-0x10ffff)
155      */
156     public boolean isPrintable(char ch) {
157         if(ch <= this.lastPrintable)
158             return true;
159         if(nioCharEncoder != null)
160             return nioCharEncoder.canEncode(ch);
161
162         //We should not reach here , if we reach due to
163 //charset not supporting encoding then fgConvertersAvailable
164 //should take care of returning false.
165
166         if(fCharToByteConverter == null) {
167             if(fHaveTriedCToB || !fgConvertersAvailable) {
168                 // forget it; nothing we can do...
169 return false;
170             }
171             if (fArgsForMethod == null) {
172                 fArgsForMethod = new Object JavaDoc [1];
173             }
174             // try and create it:
175 try {
176                 fArgsForMethod[0] = javaName;
177                 fCharToByteConverter = fgGetConverterMethod.invoke(null, fArgsForMethod);
178             } catch(Exception JavaDoc e) {
179                 // don't try it again...
180 fHaveTriedCToB = true;
181                 return false;
182             }
183         }
184         try {
185             fArgsForMethod[0] = new Character JavaDoc(ch);
186             return ((Boolean JavaDoc) fgCanConvertMethod.invoke(fCharToByteConverter, fArgsForMethod)).booleanValue();
187         } catch (Exception JavaDoc e) {
188             // obviously can't use this converter; probably some kind of
189 // security restriction
190 fCharToByteConverter = null;
191             fHaveTriedCToB = false;
192             return false;
193         }
194     }
195
196     // is this an encoding name recognized by this JDK?
197 // if not, will throw UnsupportedEncodingException
198 public static void testJavaEncodingName(String JavaDoc name) throws UnsupportedEncodingException JavaDoc {
199         final byte [] bTest = {(byte)'v', (byte)'a', (byte)'l', (byte)'i', (byte)'d'};
200         String JavaDoc s = new String JavaDoc(bTest, name);
201     }
202     
203     // Attempt to get methods for char to byte
204 // converter on class initialization.
205 static {
206         try {
207             Class JavaDoc clazz = Class.forName("sun.io.CharToByteConverter");
208             fgGetConverterMethod = clazz.getMethod("getConverter", new Class JavaDoc [] {String JavaDoc.class});
209             fgCanConvertMethod = clazz.getMethod("canConvert", new Class JavaDoc [] {Character.TYPE});
210             fgConvertersAvailable = true;
211         }
212         // ClassNotFoundException, NoSuchMethodException or SecurityException
213 // Whatever the case, we cannot use sun.io.CharToByteConverter.
214 catch (Exception JavaDoc exc) {
215             fgGetConverterMethod = null;
216             fgCanConvertMethod = null;
217             fgConvertersAvailable = false;
218         }
219     }
220 }
221
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