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1   /*
2    * Copyright (c) 1995, 2005, Oracle and/or its affiliates. All rights reserved.
3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4    *
5    * This code is free software; you can redistribute it and/or modify it
6    * under the terms of the GNU General Public License version 2 only, as
7    * published by the Free Software Foundation.  Oracle designates this
8    * particular file as subject to the "Classpath" exception as provided
9    * by Oracle in the LICENSE file that accompanied this code.
10   *
11   * This code is distributed in the hope that it will be useful, but WITHOUT
12   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14   * version 2 for more details (a copy is included in the LICENSE file that
15   * accompanied this code).
16   *
17   * You should have received a copy of the GNU General Public License version
18   * 2 along with this work; if not, write to the Free Software Foundation,
19   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20   *
21   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22   * or visit www.oracle.com if you need additional information or have any
23   * questions.
24   */
25  
26  package sun.misc;
27  
28  import java.io.InputStream;
29  import java.io.ByteArrayInputStream;
30  import java.io.OutputStream;
31  import java.io.ByteArrayOutputStream;
32  import java.io.PrintStream;
33  import java.io.IOException;
34  import java.nio.ByteBuffer;
35  
36  
37  /**
38   * This class defines the encoding half of character encoders.
39   * A character encoder is an algorithim for transforming 8 bit binary
40   * data into text (generally 7 bit ASCII or 8 bit ISO-Latin-1 text)
41   * for transmition over text channels such as e-mail and network news.
42   *
43   * The character encoders have been structured around a central theme
44   * that, in general, the encoded text has the form:
45   *
46   * <pre>
47   *      [Buffer Prefix]
48   *      [Line Prefix][encoded data atoms][Line Suffix]
49   *      [Buffer Suffix]
50   * </pre>
51   *
52   * In the CharacterEncoder and CharacterDecoder classes, one complete
53   * chunk of data is referred to as a <i>buffer</i>. Encoded buffers
54   * are all text, and decoded buffers (sometimes just referred to as
55   * buffers) are binary octets.
56   *
57   * To create a custom encoder, you must, at a minimum,  overide three
58   * abstract methods in this class.
59   * <DL>
60   * <DD>bytesPerAtom which tells the encoder how many bytes to
61   * send to encodeAtom
62   * <DD>encodeAtom which encodes the bytes sent to it as text.
63   * <DD>bytesPerLine which tells the encoder the maximum number of
64   * bytes per line.
65   * </DL>
66   *
67   * Several useful encoders have already been written and are
68   * referenced in the See Also list below.
69   *
70   * @author      Chuck McManis
71   * @see         CharacterDecoder;
72   * @see         UCEncoder
73   * @see         UUEncoder
74   * @see         BASE64Encoder
75   */
76  public abstract class CharacterEncoder {
77  
78      /** Stream that understands "printing" */
79      protected PrintStream pStream;
80  
81      /** Return the number of bytes per atom of encoding */
82      abstract protected int bytesPerAtom();
83  
84      /** Return the number of bytes that can be encoded per line */
85      abstract protected int bytesPerLine();
86  
87      /**
88       * Encode the prefix for the entire buffer. By default is simply
89       * opens the PrintStream for use by the other functions.
90       */
91      protected void encodeBufferPrefix(OutputStream aStream) throws IOException {
92          pStream = new PrintStream(aStream);
93      }
94  
95      /**
96       * Encode the suffix for the entire buffer.
97       */
98      protected void encodeBufferSuffix(OutputStream aStream) throws IOException {
99      }
100 
101     /**
102      * Encode the prefix that starts every output line.
103      */
104     protected void encodeLinePrefix(OutputStream aStream, int aLength)
105     throws IOException {
106     }
107 
108     /**
109      * Encode the suffix that ends every output line. By default
110      * this method just prints a <newline> into the output stream.
111      */
112     protected void encodeLineSuffix(OutputStream aStream) throws IOException {
113         pStream.println();
114     }
115 
116     /** Encode one "atom" of information into characters. */
117     abstract protected void encodeAtom(OutputStream aStream, byte someBytes[],
118                 int anOffset, int aLength) throws IOException;
119 
120     /**
121      * This method works around the bizarre semantics of BufferedInputStream's
122      * read method.
123      */
124     protected int readFully(InputStream in, byte buffer[])
125         throws java.io.IOException {
126         for (int i = 0; i < buffer.length; i++) {
127             int q = in.read();
128             if (q == -1)
129                 return i;
130             buffer[i] = (byte)q;
131         }
132         return buffer.length;
133     }
134 
135     /**
136      * Encode bytes from the input stream, and write them as text characters
137      * to the output stream. This method will run until it exhausts the
138      * input stream, but does not print the line suffix for a final
139      * line that is shorter than bytesPerLine().
140      */
141     public void encode(InputStream inStream, OutputStream outStream)
142         throws IOException {
143         int     j;
144         int     numBytes;
145         byte    tmpbuffer[] = new byte[bytesPerLine()];
146 
147         encodeBufferPrefix(outStream);
148 
149         while (true) {
150             numBytes = readFully(inStream, tmpbuffer);
151             if (numBytes == 0) {
152                 break;
153             }
154             encodeLinePrefix(outStream, numBytes);
155             for (j = 0; j < numBytes; j += bytesPerAtom()) {
156 
157                 if ((j + bytesPerAtom()) <= numBytes) {
158                     encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
159                 } else {
160                     encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
161                 }
162             }
163             if (numBytes < bytesPerLine()) {
164                 break;
165             } else {
166                 encodeLineSuffix(outStream);
167             }
168         }
169         encodeBufferSuffix(outStream);
170     }
171 
172     /**
173      * Encode the buffer in <i>aBuffer</i> and write the encoded
174      * result to the OutputStream <i>aStream</i>.
175      */
176     public void encode(byte aBuffer[], OutputStream aStream)
177     throws IOException {
178         ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
179         encode(inStream, aStream);
180     }
181 
182     /**
183      * A 'streamless' version of encode that simply takes a buffer of
184      * bytes and returns a string containing the encoded buffer.
185      */
186     public String encode(byte aBuffer[]) {
187         ByteArrayOutputStream   outStream = new ByteArrayOutputStream();
188         ByteArrayInputStream    inStream = new ByteArrayInputStream(aBuffer);
189         String retVal = null;
190         try {
191             encode(inStream, outStream);
192             // explicit ascii->unicode conversion
193             retVal = outStream.toString("8859_1");
194         } catch (Exception IOException) {
195             // This should never happen.
196             throw new Error("CharacterEncoder.encode internal error");
197         }
198         return (retVal);
199     }
200 
201     /**
202      * Return a byte array from the remaining bytes in this ByteBuffer.
203      * <P>
204      * The ByteBuffer's position will be advanced to ByteBuffer's limit.
205      * <P>
206      * To avoid an extra copy, the implementation will attempt to return the
207      * byte array backing the ByteBuffer.  If this is not possible, a
208      * new byte array will be created.
209      */
210     private byte [] getBytes(ByteBuffer bb) {
211         /*
212          * This should never return a BufferOverflowException, as we're
213          * careful to allocate just the right amount.
214          */
215         byte [] buf = null;
216 
217         /*
218          * If it has a usable backing byte buffer, use it.  Use only
219          * if the array exactly represents the current ByteBuffer.
220          */
221         if (bb.hasArray()) {
222             byte [] tmp = bb.array();
223             if ((tmp.length == bb.capacity()) &&
224                     (tmp.length == bb.remaining())) {
225                 buf = tmp;
226                 bb.position(bb.limit());
227             }
228         }
229 
230         if (buf == null) {
231             /*
232              * This class doesn't have a concept of encode(buf, len, off),
233              * so if we have a partial buffer, we must reallocate
234              * space.
235              */
236             buf = new byte[bb.remaining()];
237 
238             /*
239              * position() automatically updated
240              */
241             bb.get(buf);
242         }
243 
244         return buf;
245     }
246 
247     /**
248      * Encode the <i>aBuffer</i> ByteBuffer and write the encoded
249      * result to the OutputStream <i>aStream</i>.
250      * <P>
251      * The ByteBuffer's position will be advanced to ByteBuffer's limit.
252      */
253     public void encode(ByteBuffer aBuffer, OutputStream aStream)
254         throws IOException {
255         byte [] buf = getBytes(aBuffer);
256         encode(buf, aStream);
257     }
258 
259     /**
260      * A 'streamless' version of encode that simply takes a ByteBuffer
261      * and returns a string containing the encoded buffer.
262      * <P>
263      * The ByteBuffer's position will be advanced to ByteBuffer's limit.
264      */
265     public String encode(ByteBuffer aBuffer) {
266         byte [] buf = getBytes(aBuffer);
267         return encode(buf);
268     }
269 
270     /**
271      * Encode bytes from the input stream, and write them as text characters
272      * to the output stream. This method will run until it exhausts the
273      * input stream. It differs from encode in that it will add the
274      * line at the end of a final line that is shorter than bytesPerLine().
275      */
276     public void encodeBuffer(InputStream inStream, OutputStream outStream)
277         throws IOException {
278         int     j;
279         int     numBytes;
280         byte    tmpbuffer[] = new byte[bytesPerLine()];
281 
282         encodeBufferPrefix(outStream);
283 
284         while (true) {
285             numBytes = readFully(inStream, tmpbuffer);
286             if (numBytes == 0) {
287                 break;
288             }
289             encodeLinePrefix(outStream, numBytes);
290             for (j = 0; j < numBytes; j += bytesPerAtom()) {
291                 if ((j + bytesPerAtom()) <= numBytes) {
292                     encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
293                 } else {
294                     encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
295                 }
296             }
297             encodeLineSuffix(outStream);
298             if (numBytes < bytesPerLine()) {
299                 break;
300             }
301         }
302         encodeBufferSuffix(outStream);
303     }
304 
305     /**
306      * Encode the buffer in <i>aBuffer</i> and write the encoded
307      * result to the OutputStream <i>aStream</i>.
308      */
309     public void encodeBuffer(byte aBuffer[], OutputStream aStream)
310     throws IOException {
311         ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
312         encodeBuffer(inStream, aStream);
313     }
314 
315     /**
316      * A 'streamless' version of encode that simply takes a buffer of
317      * bytes and returns a string containing the encoded buffer.
318      */
319     public String encodeBuffer(byte aBuffer[]) {
320         ByteArrayOutputStream   outStream = new ByteArrayOutputStream();
321         ByteArrayInputStream    inStream = new ByteArrayInputStream(aBuffer);
322         try {
323             encodeBuffer(inStream, outStream);
324         } catch (Exception IOException) {
325             // This should never happen.
326             throw new Error("CharacterEncoder.encodeBuffer internal error");
327         }
328         return (outStream.toString());
329     }
330 
331     /**
332      * Encode the <i>aBuffer</i> ByteBuffer and write the encoded
333      * result to the OutputStream <i>aStream</i>.
334      * <P>
335      * The ByteBuffer's position will be advanced to ByteBuffer's limit.
336      */
337     public void encodeBuffer(ByteBuffer aBuffer, OutputStream aStream)
338         throws IOException {
339         byte [] buf = getBytes(aBuffer);
340         encodeBuffer(buf, aStream);
341     }
342 
343     /**
344      * A 'streamless' version of encode that simply takes a ByteBuffer
345      * and returns a string containing the encoded buffer.
346      * <P>
347      * The ByteBuffer's position will be advanced to ByteBuffer's limit.
348      */
349     public String encodeBuffer(ByteBuffer aBuffer) {
350         byte [] buf = getBytes(aBuffer);
351         return encodeBuffer(buf);
352     }
353 
354 }