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| 1 | /* | ||
| 2 | * Copyright (c) 1995, 2004, 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.OutputStream; | ||
| 29 | import java.io.ByteArrayOutputStream; | ||
| 30 | import java.io.InputStream; | ||
| 31 | import java.io.PushbackInputStream; | ||
| 32 | import java.io.ByteArrayInputStream; | ||
| 33 | import java.io.IOException; | ||
| 34 | import java.nio.ByteBuffer; | ||
| 35 | |||
| 36 | /** | ||
| 37 | * This class defines the decoding half of character encoders. | ||
| 38 | * A character decoder is an algorithim for transforming 8 bit | ||
| 39 | * binary data that has been encoded into text by a character | ||
| 40 | * encoder, back into original binary form. | ||
| 41 | * | ||
| 42 | * The character encoders, in general, have been structured | ||
| 43 | * around a central theme that binary data can be encoded into | ||
| 44 | * text that has the form: | ||
| 45 | * | ||
| 46 | * <pre> | ||
| 47 | * [Buffer Prefix] | ||
| 48 | * [Line Prefix][encoded data atoms][Line Suffix] | ||
| 49 | * [Buffer Suffix] | ||
| 50 | * </pre> | ||
| 51 | * | ||
| 52 | * Of course in the simplest encoding schemes, the buffer has no | ||
| 53 | * distinct prefix of suffix, however all have some fixed relationship | ||
| 54 | * between the text in an 'atom' and the binary data itself. | ||
| 55 | * | ||
| 56 | * In the CharacterEncoder and CharacterDecoder classes, one complete | ||
| 57 | * chunk of data is referred to as a <i>buffer</i>. Encoded buffers | ||
| 58 | * are all text, and decoded buffers (sometimes just referred to as | ||
| 59 | * buffers) are binary octets. | ||
| 60 | * | ||
| 61 | * To create a custom decoder, you must, at a minimum, overide three | ||
| 62 | * abstract methods in this class. | ||
| 63 | * <DL> | ||
| 64 | * <DD>bytesPerAtom which tells the decoder how many bytes to | ||
| 65 | * expect from decodeAtom | ||
| 66 | * <DD>decodeAtom which decodes the bytes sent to it as text. | ||
| 67 | * <DD>bytesPerLine which tells the encoder the maximum number of | ||
| 68 | * bytes per line. | ||
| 69 | * </DL> | ||
| 70 | * | ||
| 71 | * In general, the character decoders return error in the form of a | ||
| 72 | * CEFormatException. The syntax of the detail string is | ||
| 73 | * <pre> | ||
| 74 | * DecoderClassName: Error message. | ||
| 75 | * </pre> | ||
| 76 | * | ||
| 77 | * Several useful decoders have already been written and are | ||
| 78 | * referenced in the See Also list below. | ||
| 79 | * | ||
| 80 | * @author Chuck McManis | ||
| 81 | * @see CEFormatException | ||
| 82 | * @see CharacterEncoder | ||
| 83 | * @see UCDecoder | ||
| 84 | * @see UUDecoder | ||
| 85 | * @see BASE64Decoder | ||
| 86 | */ | ||
| 87 | |||
| 88 | public abstract class CharacterDecoder { | ||
| 89 | |||
| 90 | /** Return the number of bytes per atom of decoding */ | ||
| 91 | abstract protected int bytesPerAtom(); | ||
| 92 | |||
| 93 | /** Return the maximum number of bytes that can be encoded per line */ | ||
| 94 | abstract protected int bytesPerLine(); | ||
| 95 | |||
| 96 | /** decode the beginning of the buffer, by default this is a NOP. */ | ||
| 97 | protected void decodeBufferPrefix(PushbackInputStream aStream, OutputStream bStream) throws IOException { } | ||
| 98 | |||
| 99 | /** decode the buffer suffix, again by default it is a NOP. */ | ||
| 100 | protected void decodeBufferSuffix(PushbackInputStream aStream, OutputStream bStream) throws IOException { } | ||
| 101 | |||
| 102 | /** | ||
| 103 | * This method should return, if it knows, the number of bytes | ||
| 104 | * that will be decoded. Many formats such as uuencoding provide | ||
| 105 | * this information. By default we return the maximum bytes that | ||
| 106 | * could have been encoded on the line. | ||
| 107 | */ | ||
| 108 | protected int decodeLinePrefix(PushbackInputStream aStream, OutputStream bStream) throws IOException { | ||
| 109 | return (bytesPerLine()); | ||
| 110 | } | ||
| 111 | |||
| 112 | /** | ||
| 113 | * This method post processes the line, if there are error detection | ||
| 114 | * or correction codes in a line, they are generally processed by | ||
| 115 | * this method. The simplest version of this method looks for the | ||
| 116 | * (newline) character. | ||
| 117 | */ | ||
| 118 | protected void decodeLineSuffix(PushbackInputStream aStream, OutputStream bStream) throws IOException { } | ||
| 119 | |||
| 120 | /** | ||
| 121 | * This method does an actual decode. It takes the decoded bytes and | ||
| 122 | * writes them to the OutputStream. The integer <i>l</i> tells the | ||
| 123 | * method how many bytes are required. This is always <= bytesPerAtom(). | ||
| 124 | */ | ||
| 125 | protected void decodeAtom(PushbackInputStream aStream, OutputStream bStream, int l) throws IOException { | ||
| 126 | throw new CEStreamExhausted(); | ||
| 127 | } | ||
| 128 | |||
| 129 | /** | ||
| 130 | * This method works around the bizarre semantics of BufferedInputStream's | ||
| 131 | * read method. | ||
| 132 | */ | ||
| 133 | protected int readFully(InputStream in, byte buffer[], int offset, int len) | ||
| 134 | throws java.io.IOException { | ||
| 135 | for (int i = 0; i < len; i++) { | ||
| 136 | int q = in.read(); | ||
| 137 | if (q == -1) | ||
| 138 | return ((i == 0) ? -1 : i); | ||
| 139 | buffer[i+offset] = (byte)q; | ||
| 140 | } | ||
| 141 | return len; | ||
| 142 | } | ||
| 143 | |||
| 144 | /** | ||
| 145 | * Decode the text from the InputStream and write the decoded | ||
| 146 | * octets to the OutputStream. This method runs until the stream | ||
| 147 | * is exhausted. | ||
| 148 | * @exception CEFormatException An error has occured while decoding | ||
| 149 | * @exception CEStreamExhausted The input stream is unexpectedly out of data | ||
| 150 | */ | ||
| 151 | public void decodeBuffer(InputStream aStream, OutputStream bStream) throws IOException { | ||
| 152 | int i; | ||
| 153 | int totalBytes = 0; | ||
| 154 | |||
| 155 | PushbackInputStream ps = new PushbackInputStream (aStream); | ||
| 156 | decodeBufferPrefix(ps, bStream); | ||
| 157 | while (true) { | ||
| 158 | int length; | ||
| 159 | |||
| 160 | try { | ||
| 161 | length = decodeLinePrefix(ps, bStream); | ||
| 162 | for (i = 0; (i+bytesPerAtom()) < length; i += bytesPerAtom()) { | ||
| 163 | decodeAtom(ps, bStream, bytesPerAtom()); | ||
| 164 | totalBytes += bytesPerAtom(); | ||
| 165 | } | ||
| 166 | if ((i + bytesPerAtom()) == length) { | ||
| 167 | decodeAtom(ps, bStream, bytesPerAtom()); | ||
| 168 | totalBytes += bytesPerAtom(); | ||
| 169 | } else { | ||
| 170 | decodeAtom(ps, bStream, length - i); | ||
| 171 | totalBytes += (length - i); | ||
| 172 | } | ||
| 173 | decodeLineSuffix(ps, bStream); | ||
| 174 | } catch (CEStreamExhausted e) { | ||
| 175 | break; | ||
| 176 | } | ||
| 177 | } | ||
| 178 | decodeBufferSuffix(ps, bStream); | ||
| 179 | } | ||
| 180 | |||
| 181 | /** | ||
| 182 | * Alternate decode interface that takes a String containing the encoded | ||
| 183 | * buffer and returns a byte array containing the data. | ||
| 184 | * @exception CEFormatException An error has occured while decoding | ||
| 185 | */ | ||
| 186 | public byte decodeBuffer(String inputString)[] throws IOException { | ||
| 187 | byte inputBuffer[] = new byte[inputString.length()]; | ||
| 188 | ByteArrayInputStream inStream; | ||
| 189 | ByteArrayOutputStream outStream; | ||
| 190 | |||
| 191 | inputString.getBytes(0, inputString.length(), inputBuffer, 0); | ||
| 192 | inStream = new ByteArrayInputStream(inputBuffer); | ||
| 193 | outStream = new ByteArrayOutputStream(); | ||
| 194 | decodeBuffer(inStream, outStream); | ||
| 195 | return (outStream.toByteArray()); | ||
| 196 | } | ||
| 197 | |||
| 198 | /** | ||
| 199 | * Decode the contents of the inputstream into a buffer. | ||
| 200 | */ | ||
| 201 | public byte decodeBuffer(InputStream in)[] throws IOException { | ||
| 202 | ByteArrayOutputStream outStream = new ByteArrayOutputStream(); | ||
| 203 | decodeBuffer(in, outStream); | ||
| 204 | return (outStream.toByteArray()); | ||
| 205 | } | ||
| 206 | |||
| 207 | /** | ||
| 208 | * Decode the contents of the String into a ByteBuffer. | ||
| 209 | */ | ||
| 210 | public ByteBuffer decodeBufferToByteBuffer(String inputString) | ||
| 211 | throws IOException { | ||
| 212 | return ByteBuffer.wrap(decodeBuffer(inputString)); | ||
| 213 | } | ||
| 214 | |||
| 215 | /** | ||
| 216 | * Decode the contents of the inputStream into a ByteBuffer. | ||
| 217 | */ | ||
| 218 | public ByteBuffer decodeBufferToByteBuffer(InputStream in) | ||
| 219 | throws IOException { | ||
| 220 | return ByteBuffer.wrap(decodeBuffer(in)); | ||
| 221 | } | ||
| 222 | } | ||