J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1996-2006 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 java.io; |
| 27 | |
| 28 | |
| 29 | /** |
| 30 | * Abstract class for reading character streams. The only methods that a |
| 31 | * subclass must implement are read(char[], int, int) and close(). Most |
| 32 | * subclasses, however, will override some of the methods defined here in order |
| 33 | * to provide higher efficiency, additional functionality, or both. |
| 34 | * |
| 35 | * |
| 36 | * @see BufferedReader |
| 37 | * @see LineNumberReader |
| 38 | * @see CharArrayReader |
| 39 | * @see InputStreamReader |
| 40 | * @see FileReader |
| 41 | * @see FilterReader |
| 42 | * @see PushbackReader |
| 43 | * @see PipedReader |
| 44 | * @see StringReader |
| 45 | * @see Writer |
| 46 | * |
| 47 | * @author Mark Reinhold |
| 48 | * @since JDK1.1 |
| 49 | */ |
| 50 | |
| 51 | public abstract class Reader implements Readable, Closeable { |
| 52 | |
| 53 | /** |
| 54 | * The object used to synchronize operations on this stream. For |
| 55 | * efficiency, a character-stream object may use an object other than |
| 56 | * itself to protect critical sections. A subclass should therefore use |
| 57 | * the object in this field rather than <tt>this</tt> or a synchronized |
| 58 | * method. |
| 59 | */ |
| 60 | protected Object lock; |
| 61 | |
| 62 | /** |
| 63 | * Creates a new character-stream reader whose critical sections will |
| 64 | * synchronize on the reader itself. |
| 65 | */ |
| 66 | protected Reader() { |
| 67 | this.lock = this; |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * Creates a new character-stream reader whose critical sections will |
| 72 | * synchronize on the given object. |
| 73 | * |
| 74 | * @param lock The Object to synchronize on. |
| 75 | */ |
| 76 | protected Reader(Object lock) { |
| 77 | if (lock == null) { |
| 78 | throw new NullPointerException(); |
| 79 | } |
| 80 | this.lock = lock; |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Attempts to read characters into the specified character buffer. |
| 85 | * The buffer is used as a repository of characters as-is: the only |
| 86 | * changes made are the results of a put operation. No flipping or |
| 87 | * rewinding of the buffer is performed. |
| 88 | * |
| 89 | * @param target the buffer to read characters into |
| 90 | * @return The number of characters added to the buffer, or |
| 91 | * -1 if this source of characters is at its end |
| 92 | * @throws IOException if an I/O error occurs |
| 93 | * @throws NullPointerException if target is null |
| 94 | * @throws ReadOnlyBufferException if target is a read only buffer |
| 95 | * @since 1.5 |
| 96 | */ |
| 97 | public int read(java.nio.CharBuffer target) throws IOException { |
| 98 | int len = target.remaining(); |
| 99 | char[] cbuf = new char[len]; |
| 100 | int n = read(cbuf, 0, len); |
| 101 | if (n > 0) |
| 102 | target.put(cbuf, 0, n); |
| 103 | return n; |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * Reads a single character. This method will block until a character is |
| 108 | * available, an I/O error occurs, or the end of the stream is reached. |
| 109 | * |
| 110 | * <p> Subclasses that intend to support efficient single-character input |
| 111 | * should override this method. |
| 112 | * |
| 113 | * @return The character read, as an integer in the range 0 to 65535 |
| 114 | * (<tt>0x00-0xffff</tt>), or -1 if the end of the stream has |
| 115 | * been reached |
| 116 | * |
| 117 | * @exception IOException If an I/O error occurs |
| 118 | */ |
| 119 | public int read() throws IOException { |
| 120 | char cb[] = new char[1]; |
| 121 | if (read(cb, 0, 1) == -1) |
| 122 | return -1; |
| 123 | else |
| 124 | return cb[0]; |
| 125 | } |
| 126 | |
| 127 | /** |
| 128 | * Reads characters into an array. This method will block until some input |
| 129 | * is available, an I/O error occurs, or the end of the stream is reached. |
| 130 | * |
| 131 | * @param cbuf Destination buffer |
| 132 | * |
| 133 | * @return The number of characters read, or -1 |
| 134 | * if the end of the stream |
| 135 | * has been reached |
| 136 | * |
| 137 | * @exception IOException If an I/O error occurs |
| 138 | */ |
| 139 | public int read(char cbuf[]) throws IOException { |
| 140 | return read(cbuf, 0, cbuf.length); |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * Reads characters into a portion of an array. This method will block |
| 145 | * until some input is available, an I/O error occurs, or the end of the |
| 146 | * stream is reached. |
| 147 | * |
| 148 | * @param cbuf Destination buffer |
| 149 | * @param off Offset at which to start storing characters |
| 150 | * @param len Maximum number of characters to read |
| 151 | * |
| 152 | * @return The number of characters read, or -1 if the end of the |
| 153 | * stream has been reached |
| 154 | * |
| 155 | * @exception IOException If an I/O error occurs |
| 156 | */ |
| 157 | abstract public int read(char cbuf[], int off, int len) throws IOException; |
| 158 | |
| 159 | /** Maximum skip-buffer size */ |
| 160 | private static final int maxSkipBufferSize = 8192; |
| 161 | |
| 162 | /** Skip buffer, null until allocated */ |
| 163 | private char skipBuffer[] = null; |
| 164 | |
| 165 | /** |
| 166 | * Skips characters. This method will block until some characters are |
| 167 | * available, an I/O error occurs, or the end of the stream is reached. |
| 168 | * |
| 169 | * @param n The number of characters to skip |
| 170 | * |
| 171 | * @return The number of characters actually skipped |
| 172 | * |
| 173 | * @exception IllegalArgumentException If <code>n</code> is negative. |
| 174 | * @exception IOException If an I/O error occurs |
| 175 | */ |
| 176 | public long skip(long n) throws IOException { |
| 177 | if (n < 0L) |
| 178 | throw new IllegalArgumentException("skip value is negative"); |
| 179 | int nn = (int) Math.min(n, maxSkipBufferSize); |
| 180 | synchronized (lock) { |
| 181 | if ((skipBuffer == null) || (skipBuffer.length < nn)) |
| 182 | skipBuffer = new char[nn]; |
| 183 | long r = n; |
| 184 | while (r > 0) { |
| 185 | int nc = read(skipBuffer, 0, (int)Math.min(r, nn)); |
| 186 | if (nc == -1) |
| 187 | break; |
| 188 | r -= nc; |
| 189 | } |
| 190 | return n - r; |
| 191 | } |
| 192 | } |
| 193 | |
| 194 | /** |
| 195 | * Tells whether this stream is ready to be read. |
| 196 | * |
| 197 | * @return True if the next read() is guaranteed not to block for input, |
| 198 | * false otherwise. Note that returning false does not guarantee that the |
| 199 | * next read will block. |
| 200 | * |
| 201 | * @exception IOException If an I/O error occurs |
| 202 | */ |
| 203 | public boolean ready() throws IOException { |
| 204 | return false; |
| 205 | } |
| 206 | |
| 207 | /** |
| 208 | * Tells whether this stream supports the mark() operation. The default |
| 209 | * implementation always returns false. Subclasses should override this |
| 210 | * method. |
| 211 | * |
| 212 | * @return true if and only if this stream supports the mark operation. |
| 213 | */ |
| 214 | public boolean markSupported() { |
| 215 | return false; |
| 216 | } |
| 217 | |
| 218 | /** |
| 219 | * Marks the present position in the stream. Subsequent calls to reset() |
| 220 | * will attempt to reposition the stream to this point. Not all |
| 221 | * character-input streams support the mark() operation. |
| 222 | * |
| 223 | * @param readAheadLimit Limit on the number of characters that may be |
| 224 | * read while still preserving the mark. After |
| 225 | * reading this many characters, attempting to |
| 226 | * reset the stream may fail. |
| 227 | * |
| 228 | * @exception IOException If the stream does not support mark(), |
| 229 | * or if some other I/O error occurs |
| 230 | */ |
| 231 | public void mark(int readAheadLimit) throws IOException { |
| 232 | throw new IOException("mark() not supported"); |
| 233 | } |
| 234 | |
| 235 | /** |
| 236 | * Resets the stream. If the stream has been marked, then attempt to |
| 237 | * reposition it at the mark. If the stream has not been marked, then |
| 238 | * attempt to reset it in some way appropriate to the particular stream, |
| 239 | * for example by repositioning it to its starting point. Not all |
| 240 | * character-input streams support the reset() operation, and some support |
| 241 | * reset() without supporting mark(). |
| 242 | * |
| 243 | * @exception IOException If the stream has not been marked, |
| 244 | * or if the mark has been invalidated, |
| 245 | * or if the stream does not support reset(), |
| 246 | * or if some other I/O error occurs |
| 247 | */ |
| 248 | public void reset() throws IOException { |
| 249 | throw new IOException("reset() not supported"); |
| 250 | } |
| 251 | |
| 252 | /** |
| 253 | * Closes the stream and releases any system resources associated with |
| 254 | * it. Once the stream has been closed, further read(), ready(), |
| 255 | * mark(), reset(), or skip() invocations will throw an IOException. |
| 256 | * Closing a previously closed stream has no effect. |
| 257 | * |
| 258 | * @exception IOException If an I/O error occurs |
| 259 | */ |
| 260 | abstract public void close() throws IOException; |
| 261 | |
| 262 | } |