SerializerTraceWriter


1   /*
2    * Copyright 2003-2004 The Apache Software Foundation.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  /*
17   * $Id: SerializerTraceWriter.java,v 1.2 2004/02/17 04:18:18 minchau Exp $
18   */
19  package org.apache.xml.serializer;
20  
21  import java.io.IOException  ;
22  import java.io.Writer  ;
23  
24  /**
25   * This class wraps the real writer, it only purpose is to send
26   * CHARACTERTOSTREAM events to the trace listener. 
27   * Each method immediately sends the call to the wrapped writer unchanged, but
28   * in addition it collects characters to be issued to a trace listener.
29   * 
30   * In this way the trace
31   * listener knows what characters have been written to the output Writer.
32   * 
33   * There may still be differences in what the trace events say is going to the
34   * output writer and what is really going there. These differences will be due
35   * to the fact that this class is UTF-8 encoding before emiting the trace event
36   * and the underlying writer may not be UTF-8 encoding. There may also be
37   * encoding differences.  So the main pupose of this class is to provide a
38   * resonable facsimile of the true output.
39   *
40   */
41  public class SerializerTraceWriter extends Writer  
42  {
43  
44      /** The real writer to immediately write to.
45       * This reference may be null, in which case nothing is written out, but
46       * only the trace events are fired for output.
47       */
48      private final java.io.Writer   m_writer;
49  
50      /** The tracer to send events to */
51      private final SerializerTrace m_tracer;
52  
53      /** The size of the internal buffer, just to keep too many
54       * events from being sent to the tracer
55       */
56      private int buf_length;
57  
58      /**
59       * Internal buffer to collect the characters to go to the trace listener.
60       * 
61       */
62      private byte buf[];
63  
64      /**
65       * How many bytes have been collected and still need to go to trace
66       * listener.
67       */
68      private int count;
69  
70      /**
71       * Creates or replaces the internal buffer, and makes sure it has a few
72       * extra bytes slight overflow of the last UTF8 encoded character.
73       * @param size
74       */
75      private void setBufferSize(int size)
76      {
77          buf = new byte[size + 3];
78          buf_length = size;
79          count = 0;
80      }
81  
82      /**
83       * Constructor.
84       * If the writer passed in is null, then this SerializerTraceWriter will
85       * only signal trace events of what would have been written to that writer.
86       * If the writer passed in is not null then the trace events will mirror
87       * what is going to that writer. In this way tools, such as a debugger, can
88       * gather information on what is being written out.
89       * 
90       * @param out the Writer to write to (possibly null)
91       * @param tracer the tracer to inform that characters are being written
92       */
93      public SerializerTraceWriter(Writer   out, SerializerTrace tracer)
94      {
95          m_writer = out;
96          m_tracer = tracer;
97          setBufferSize(1024);
98      }
99  
100     /**
101      * Flush out the collected characters by sending them to the trace
102      * listener.  These characters are never written to the real writer
103      * (m_writer) because that has already happened with every method
104      * call. This method simple informs the listener of what has already
105      * happened.
106      * @throws IOException
107      */
108     private void flushBuffer() throws IOException  
109     {
110 
111         // Just for tracing purposes
112         if (count > 0)
113         {
114             char[] chars = new char[count];
115             for(int i=0; i<count; i++)
116                 chars[i] = (char) buf[i];
117 
118             if (m_tracer != null)
119                 m_tracer.fireGenerateEvent(
120                     SerializerTrace.EVENTTYPE_OUTPUT_CHARACTERS,
121                     chars,
122                     0,
123                     chars.length);
124 
125             count = 0;
126         }
127     }
128 
129     /**
130      * Flush the internal buffer and flush the Writer
131      * @see java.io.Writer#flush()
132      */
133     public void flush() throws java.io.IOException  
134     {
135         // send to the real writer
136         if (m_writer != null)
137             m_writer.flush();
138 
139         // from here on just for tracing purposes
140         flushBuffer();
141     }
142 
143     /**
144      * Flush the internal buffer and close the Writer
145      * @see java.io.Writer#close()
146      */
147     public void close() throws java.io.IOException  
148     {
149         // send to the real writer
150         if (m_writer != null)   
151             m_writer.close();
152 
153         // from here on just for tracing purposes
154         flushBuffer();
155     }
156 
157 
158     /**
159      * Write a single character.  The character to be written is contained in
160      * the 16 low-order bits of the given integer value; the 16 high-order bits
161      * are ignored.
162      *
163      * <p> Subclasses that intend to support efficient single-character output
164      * should override this method.
165      *
166      * @param c  int specifying a character to be written.
167      * @exception  IOException  If an I/O error occurs
168      */
169     public void write(final int c) throws IOException  
170     {
171         // send to the real writer
172         if (m_writer != null)
173             m_writer.write(c);
174 
175         // ---------- from here on just collect for tracing purposes
176 
177         /* If we are close to the end of the buffer then flush it.
178          * Remember the buffer can hold a few more characters than buf_length
179          */
180         if (count >= buf_length)
181             flushBuffer();
182 
183         if (c < 0x80)
184         {
185             buf[count++] = (byte) (c);
186         }
187         else if (c < 0x800)
188         {
189             buf[count++] = (byte) (0xc0 + (c >> 6));
190             buf[count++] = (byte) (0x80 + (c & 0x3f));
191         }
192         else
193         {
194             buf[count++] = (byte) (0xe0 + (c >> 12));
195             buf[count++] = (byte) (0x80 + ((c >> 6) & 0x3f));
196             buf[count++] = (byte) (0x80 + (c & 0x3f));
197         }
198     }
199 
200     /**
201      * Write a portion of an array of characters.
202      *
203      * @param  chars  Array of characters
204      * @param  start   Offset from which to start writing characters
205      * @param  length   Number of characters to write
206      *
207      * @exception  IOException  If an I/O error occurs
208      *
209      * @throws java.io.IOException
210      */
211     public void write(final char chars[], final int start, final int length)
212         throws java.io.IOException  
213     {
214         // send to the real writer
215         if (m_writer != null)
216             m_writer.write(chars, start, length);
217 
218         // from here on just collect for tracing purposes
219         int lengthx3 = (length << 1) + length;
220 
221         if (lengthx3 >= buf_length)
222         {
223 
224             /* If the request length exceeds the size of the output buffer,
225               * flush the output buffer and make the buffer bigger to handle.
226               */
227 
228             flushBuffer();
229             setBufferSize(2 * lengthx3);
230 
231         }
232 
233         if (lengthx3 > buf_length - count)
234         {
235             flushBuffer();
236         }
237 
238         final int n = length + start;
239         for (int i = start; i < n; i++)
240         {
241             final char c = chars[i];
242 
243             if (c < 0x80)
244                 buf[count++] = (byte) (c);
245             else if (c < 0x800)
246             {
247                 buf[count++] = (byte) (0xc0 + (c >> 6));
248                 buf[count++] = (byte) (0x80 + (c & 0x3f));
249             }
250             else
251             {
252                 buf[count++] = (byte) (0xe0 + (c >> 12));
253                 buf[count++] = (byte) (0x80 + ((c >> 6) & 0x3f));
254                 buf[count++] = (byte) (0x80 + (c & 0x3f));
255             }
256         }
257 
258     }
259 
260     /**
261      * Write a string.
262      *
263      * @param  s  String to be written
264      *
265      * @exception  IOException  If an I/O error occurs
266      */
267     public void write(final String   s) throws IOException  
268     {
269         // send to the real writer
270         if (m_writer != null)
271             m_writer.write(s);
272 
273         // from here on just collect for tracing purposes
274         final int length = s.length();
275 
276         // We multiply the length by three since this is the maximum length
277         // of the characters that we can put into the buffer.  It is possible
278         // for each Unicode character to expand to three bytes.
279 
280         int lengthx3 = (length << 1) + length;
281 
282         if (lengthx3 >= buf_length)
283         {
284 
285             /* If the request length exceeds the size of the output buffer,
286               * flush the output buffer and make the buffer bigger to handle.
287               */
288 
289             flushBuffer();
290             setBufferSize(2 * lengthx3);
291         }
292 
293         if (lengthx3 > buf_length - count)
294         {
295             flushBuffer();
296         }
297 
298         for (int i = 0; i < length; i++)
299         {
300             final char c = s.charAt(i);
301 
302             if (c < 0x80)
303                 buf[count++] = (byte) (c);
304             else if (c < 0x800)
305             {
306                 buf[count++] = (byte) (0xc0 + (c >> 6));
307                 buf[count++] = (byte) (0x80 + (c & 0x3f));
308             }
309             else
310             {
311                 buf[count++] = (byte) (0xe0 + (c >> 12));
312                 buf[count++] = (byte) (0x80 + ((c >> 6) & 0x3f));
313                 buf[count++] = (byte) (0x80 + (c & 0x3f));
314             }
315         }
316     }
317 
318 }
319
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