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| 1 | +/* | |
| 2 | + * Copyright (c) 1996, 2011, 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 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 | +} | |