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/Users/lyon/j4p/src/security/CharacterEncoder.java
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1 /*
2 * @(#)CharacterEncoder.java 1.32 03/01/23
3 *
4 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
5 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
6 */
7
8 package security;
9
10 import java.io.InputStream;
11 import java.io.ByteArrayInputStream;
12 import java.io.OutputStream;
13 import java.io.ByteArrayOutputStream;
14 import java.io.PrintStream;
15 import java.io.IOException;
16
17
18 /**
19 * This class defines the encoding half of character encoders.
20 * A character encoder is an algorithim for transforming 8 bit binary
21 * data into text (generally 7 bit ASCII or 8 bit ISO-Latin-1 text)
22 * for transmition over text channels such as e-mail and network news.
23 *
24 * The character encoders have been structured around a central theme
25 * that, in general, the encoded text has the form:
26 *
27 * <pre>
28 * [Buffer Prefix]
29 * [Line Prefix][encoded data atoms][Line Suffix]
30 * [Buffer Suffix]
31 * </pre>
32 *
33 * In the CharacterEncoder and CharacterDecoder classes, one complete
34 * chunk of data is referred to as a <i>buffer</i>. Encoded buffers
35 * are all text, and decoded buffers (sometimes just referred to as
36 * buffers) are binary octets.
37 *
38 * To create a custom encoder, you must, at a minimum, overide three
39 * abstract methods in this class.
40 * <DL>
41 * <DD>bytesPerAtom which tells the encoder how many bytes to
42 * send to encodeAtom
43 * <DD>encodeAtom which encodes the bytes sent to it as text.
44 * <DD>bytesPerLine which tells the encoder the maximum number of
45 * bytes per line.
46 * </DL>
47 *
48 * Several useful encoders have already been written and are
49 * referenced in the See Also list below.
50 *
51 * @version 1.32, 01/23/03
52 * @author Chuck McManis
53 * @see BASE64Encoder
54 */
55 public abstract class CharacterEncoder {
56
57 /** Stream that understands "printing" */
58 protected PrintStream pStream;
59
60 /** Return the number of bytes per atom of encoding */
61 abstract protected int bytesPerAtom();
62
63 /** Return the number of bytes that can be encoded per line */
64 abstract protected int bytesPerLine();
65
66 /**
67 * Encode the prefix for the entire buffer. By default is simply
68 * opens the PrintStream for use by the other functions.
69 */
70 protected void encodeBufferPrefix(OutputStream aStream) throws IOException {
71 pStream = new PrintStream(aStream);
72 }
73
74 /**
75 * Encode the suffix for the entire buffer.
76 */
77 protected void encodeBufferSuffix(OutputStream aStream) throws IOException {
78 }
79
80 /**
81 * Encode the prefix that starts every output line.
82 */
83 protected void encodeLinePrefix(OutputStream aStream, int aLength)
84 throws IOException {
85 }
86
87 /**
88 * Encode the suffix that ends every output line. By default
89 * this method just prints a <newline> into the output stream.
90 */
91 protected void encodeLineSuffix(OutputStream aStream) throws IOException {
92 pStream.println();
93 }
94
95 /** Encode one "atom" of information into characters. */
96 abstract protected void encodeAtom(OutputStream aStream, byte someBytes[],
97 int anOffset, int aLength) throws IOException;
98
99 /**
100 * This method works around the bizarre semantics of BufferedInputStream's
101 * read method.
102 */
103 protected int readFully(InputStream in, byte buffer[])
104 throws java.io.IOException {
105 for (int i = 0; i < buffer.length; i++) {
106 int q = in.read();
107 if (q == -1)
108 return i;
109 buffer[i] = (byte)q;
110 }
111 return buffer.length;
112 }
113
114 /**
115 * Encode bytes from the input stream, and write them as text characters
116 * to the output stream. This method will run until it exhausts the
117 * input stream, but does not print the line suffix for a final
118 * line that is shorter than bytesPerLine().
119 */
120 public void encode(InputStream inStream, OutputStream outStream)
121 throws IOException {
122 int j;
123 int numBytes;
124 byte tmpbuffer[] = new byte[bytesPerLine()];
125
126 encodeBufferPrefix(outStream);
127
128 while (true) {
129 numBytes = readFully(inStream, tmpbuffer);
130 if (numBytes == 0) {
131 break;
132 }
133 encodeLinePrefix(outStream, numBytes);
134 for (j = 0; j < numBytes; j += bytesPerAtom()) {
135
136 if ((j + bytesPerAtom()) <= numBytes) {
137 encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
138 } else {
139 encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
140 }
141 }
142 if (numBytes < bytesPerLine()) {
143 break;
144 } else {
145 encodeLineSuffix(outStream);
146 }
147 }
148 encodeBufferSuffix(outStream);
149 }
150
151 /**
152 * Encode the buffer in <i>aBuffer</i> and write the encoded
153 * result to the OutputStream <i>aStream</i>.
154 */
155 public void encode(byte aBuffer[], OutputStream aStream)
156 throws IOException {
157 ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
158 encode(inStream, aStream);
159 }
160
161 /**
162 * A 'streamless' version of encode that simply takes a buffer of
163 * bytes and returns a string containing the encoded buffer.
164 */
165 public String encode(byte aBuffer[]) {
166 ByteArrayOutputStream outStream = new ByteArrayOutputStream();
167 ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
168 String retVal = null;
169 try {
170 encode(inStream, outStream);
171 // explicit ascii->unicode conversion
172 retVal = outStream.toString("8859_1");
173 } catch (Exception IOException) {
174 // This should never happen.
175 throw new Error("ChracterEncoder::encodeBuffer internal error");
176 }
177 return (retVal);
178 }
179
180 /**
181 * Encode bytes from the input stream, and write them as text characters
182 * to the output stream. This method will run until it exhausts the
183 * input stream. It differs from encode in that it will add the
184 * line at the end of a final line that is shorter than bytesPerLine().
185 */
186 public void encodeBuffer(InputStream inStream, OutputStream outStream)
187 throws IOException {
188 int j;
189 int numBytes;
190 byte tmpbuffer[] = new byte[bytesPerLine()];
191
192 encodeBufferPrefix(outStream);
193
194 while (true) {
195 numBytes = readFully(inStream, tmpbuffer);
196 if (numBytes == 0) {
197 break;
198 }
199 encodeLinePrefix(outStream, numBytes);
200 for (j = 0; j < numBytes; j += bytesPerAtom()) {
201 if ((j + bytesPerAtom()) <= numBytes) {
202 encodeAtom(outStream, tmpbuffer, j, bytesPerAtom());
203 } else {
204 encodeAtom(outStream, tmpbuffer, j, (numBytes)- j);
205 }
206 }
207 encodeLineSuffix(outStream);
208 if (numBytes < bytesPerLine()) {
209 break;
210 }
211 }
212 encodeBufferSuffix(outStream);
213 }
214
215 /**
216 * Encode the buffer in <i>aBuffer</i> and write the encoded
217 * result to the OutputStream <i>aStream</i>.
218 */
219 public void encodeBuffer(byte aBuffer[], OutputStream aStream)
220 throws IOException {
221 ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
222 encodeBuffer(inStream, aStream);
223 }
224
225 /**
226 * A 'streamless' version of encode that simply takes a buffer of
227 * bytes and returns a string containing the encoded buffer.
228 */
229 public String encodeBuffer(byte aBuffer[]) {
230 ByteArrayOutputStream outStream = new ByteArrayOutputStream();
231 ByteArrayInputStream inStream = new ByteArrayInputStream(aBuffer);
232 try {
233 encodeBuffer(inStream, outStream);
234 } catch (Exception IOException) {
235 // This should never happen.
236 throw new Error("ChracterEncoder::encodeBuffer internal error");
237 }
238 return (outStream.toString());
239 }
240
241 }
242