J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1995-2005 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | } |