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 | * A character-stream reader that allows characters to be pushed back into the |
| 31 | * stream. |
| 32 | * |
| 33 | * @author Mark Reinhold |
| 34 | * @since JDK1.1 |
| 35 | */ |
| 36 | |
| 37 | public class PushbackReader extends FilterReader { |
| 38 | |
| 39 | /** Pushback buffer */ |
| 40 | private char[] buf; |
| 41 | |
| 42 | /** Current position in buffer */ |
| 43 | private int pos; |
| 44 | |
| 45 | /** |
| 46 | * Creates a new pushback reader with a pushback buffer of the given size. |
| 47 | * |
| 48 | * @param in The reader from which characters will be read |
| 49 | * @param size The size of the pushback buffer |
| 50 | * @exception IllegalArgumentException if size is <= 0 |
| 51 | */ |
| 52 | public PushbackReader(Reader in, int size) { |
| 53 | super(in); |
| 54 | if (size <= 0) { |
| 55 | throw new IllegalArgumentException("size <= 0"); |
| 56 | } |
| 57 | this.buf = new char[size]; |
| 58 | this.pos = size; |
| 59 | } |
| 60 | |
| 61 | /** |
| 62 | * Creates a new pushback reader with a one-character pushback buffer. |
| 63 | * |
| 64 | * @param in The reader from which characters will be read |
| 65 | */ |
| 66 | public PushbackReader(Reader in) { |
| 67 | this(in, 1); |
| 68 | } |
| 69 | |
| 70 | /** Checks to make sure that the stream has not been closed. */ |
| 71 | private void ensureOpen() throws IOException { |
| 72 | if (buf == null) |
| 73 | throw new IOException("Stream closed"); |
| 74 | } |
| 75 | |
| 76 | /** |
| 77 | * Reads a single character. |
| 78 | * |
| 79 | * @return The character read, or -1 if the end of the stream has been |
| 80 | * reached |
| 81 | * |
| 82 | * @exception IOException If an I/O error occurs |
| 83 | */ |
| 84 | public int read() throws IOException { |
| 85 | synchronized (lock) { |
| 86 | ensureOpen(); |
| 87 | if (pos < buf.length) |
| 88 | return buf[pos++]; |
| 89 | else |
| 90 | return super.read(); |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | /** |
| 95 | * Reads characters into a portion of an array. |
| 96 | * |
| 97 | * @param cbuf Destination buffer |
| 98 | * @param off Offset at which to start writing characters |
| 99 | * @param len Maximum number of characters to read |
| 100 | * |
| 101 | * @return The number of characters read, or -1 if the end of the |
| 102 | * stream has been reached |
| 103 | * |
| 104 | * @exception IOException If an I/O error occurs |
| 105 | */ |
| 106 | public int read(char cbuf[], int off, int len) throws IOException { |
| 107 | synchronized (lock) { |
| 108 | ensureOpen(); |
| 109 | try { |
| 110 | if (len <= 0) { |
| 111 | if (len < 0) { |
| 112 | throw new IndexOutOfBoundsException(); |
| 113 | } else if ((off < 0) || (off > cbuf.length)) { |
| 114 | throw new IndexOutOfBoundsException(); |
| 115 | } |
| 116 | return 0; |
| 117 | } |
| 118 | int avail = buf.length - pos; |
| 119 | if (avail > 0) { |
| 120 | if (len < avail) |
| 121 | avail = len; |
| 122 | System.arraycopy(buf, pos, cbuf, off, avail); |
| 123 | pos += avail; |
| 124 | off += avail; |
| 125 | len -= avail; |
| 126 | } |
| 127 | if (len > 0) { |
| 128 | len = super.read(cbuf, off, len); |
| 129 | if (len == -1) { |
| 130 | return (avail == 0) ? -1 : avail; |
| 131 | } |
| 132 | return avail + len; |
| 133 | } |
| 134 | return avail; |
| 135 | } catch (ArrayIndexOutOfBoundsException e) { |
| 136 | throw new IndexOutOfBoundsException(); |
| 137 | } |
| 138 | } |
| 139 | } |
| 140 | |
| 141 | /** |
| 142 | * Pushes back a single character by copying it to the front of the |
| 143 | * pushback buffer. After this method returns, the next character to be read |
| 144 | * will have the value <code>(char)c</code>. |
| 145 | * |
| 146 | * @param c The int value representing a character to be pushed back |
| 147 | * |
| 148 | * @exception IOException If the pushback buffer is full, |
| 149 | * or if some other I/O error occurs |
| 150 | */ |
| 151 | public void unread(int c) throws IOException { |
| 152 | synchronized (lock) { |
| 153 | ensureOpen(); |
| 154 | if (pos == 0) |
| 155 | throw new IOException("Pushback buffer overflow"); |
| 156 | buf[--pos] = (char) c; |
| 157 | } |
| 158 | } |
| 159 | |
| 160 | /** |
| 161 | * Pushes back a portion of an array of characters by copying it to the |
| 162 | * front of the pushback buffer. After this method returns, the next |
| 163 | * character to be read will have the value <code>cbuf[off]</code>, the |
| 164 | * character after that will have the value <code>cbuf[off+1]</code>, and |
| 165 | * so forth. |
| 166 | * |
| 167 | * @param cbuf Character array |
| 168 | * @param off Offset of first character to push back |
| 169 | * @param len Number of characters to push back |
| 170 | * |
| 171 | * @exception IOException If there is insufficient room in the pushback |
| 172 | * buffer, or if some other I/O error occurs |
| 173 | */ |
| 174 | public void unread(char cbuf[], int off, int len) throws IOException { |
| 175 | synchronized (lock) { |
| 176 | ensureOpen(); |
| 177 | if (len > pos) |
| 178 | throw new IOException("Pushback buffer overflow"); |
| 179 | pos -= len; |
| 180 | System.arraycopy(cbuf, off, buf, pos, len); |
| 181 | } |
| 182 | } |
| 183 | |
| 184 | /** |
| 185 | * Pushes back an array of characters by copying it to the front of the |
| 186 | * pushback buffer. After this method returns, the next character to be |
| 187 | * read will have the value <code>cbuf[0]</code>, the character after that |
| 188 | * will have the value <code>cbuf[1]</code>, and so forth. |
| 189 | * |
| 190 | * @param cbuf Character array to push back |
| 191 | * |
| 192 | * @exception IOException If there is insufficient room in the pushback |
| 193 | * buffer, or if some other I/O error occurs |
| 194 | */ |
| 195 | public void unread(char cbuf[]) throws IOException { |
| 196 | unread(cbuf, 0, cbuf.length); |
| 197 | } |
| 198 | |
| 199 | /** |
| 200 | * Tells whether this stream is ready to be read. |
| 201 | * |
| 202 | * @exception IOException If an I/O error occurs |
| 203 | */ |
| 204 | public boolean ready() throws IOException { |
| 205 | synchronized (lock) { |
| 206 | ensureOpen(); |
| 207 | return (pos < buf.length) || super.ready(); |
| 208 | } |
| 209 | } |
| 210 | |
| 211 | /** |
| 212 | * Marks the present position in the stream. The <code>mark</code> |
| 213 | * for class <code>PushbackReader</code> always throws an exception. |
| 214 | * |
| 215 | * @exception IOException Always, since mark is not supported |
| 216 | */ |
| 217 | public void mark(int readAheadLimit) throws IOException { |
| 218 | throw new IOException("mark/reset not supported"); |
| 219 | } |
| 220 | |
| 221 | /** |
| 222 | * Resets the stream. The <code>reset</code> method of |
| 223 | * <code>PushbackReader</code> always throws an exception. |
| 224 | * |
| 225 | * @exception IOException Always, since reset is not supported |
| 226 | */ |
| 227 | public void reset() throws IOException { |
| 228 | throw new IOException("mark/reset not supported"); |
| 229 | } |
| 230 | |
| 231 | /** |
| 232 | * Tells whether this stream supports the mark() operation, which it does |
| 233 | * not. |
| 234 | */ |
| 235 | public boolean markSupported() { |
| 236 | return false; |
| 237 | } |
| 238 | |
| 239 | /** |
| 240 | * Closes the stream and releases any system resources associated with |
| 241 | * it. Once the stream has been closed, further read(), |
| 242 | * unread(), ready(), or skip() invocations will throw an IOException. |
| 243 | * Closing a previously closed stream has no effect. |
| 244 | * |
| 245 | * @exception IOException If an I/O error occurs |
| 246 | */ |
| 247 | public void close() throws IOException { |
| 248 | super.close(); |
| 249 | buf = null; |
| 250 | } |
| 251 | |
| 252 | /** |
| 253 | * Skips characters. This method will block until some characters are |
| 254 | * available, an I/O error occurs, or the end of the stream is reached. |
| 255 | * |
| 256 | * @param n The number of characters to skip |
| 257 | * |
| 258 | * @return The number of characters actually skipped |
| 259 | * |
| 260 | * @exception IllegalArgumentException If <code>n</code> is negative. |
| 261 | * @exception IOException If an I/O error occurs |
| 262 | */ |
| 263 | public long skip(long n) throws IOException { |
| 264 | if (n < 0L) |
| 265 | throw new IllegalArgumentException("skip value is negative"); |
| 266 | synchronized (lock) { |
| 267 | ensureOpen(); |
| 268 | int avail = buf.length - pos; |
| 269 | if (avail > 0) { |
| 270 | if (n <= avail) { |
| 271 | pos += n; |
| 272 | return n; |
| 273 | } else { |
| 274 | pos = buf.length; |
| 275 | n -= avail; |
| 276 | } |
| 277 | } |
| 278 | return avail + super.skip(n); |
| 279 | } |
| 280 | } |
| 281 | } |