J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1996-2005 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 java.io; |
| 27 | |
| 28 | |
| 29 | /** |
| 30 | * A character stream whose source is a string. |
| 31 | * |
| 32 | * @author Mark Reinhold |
| 33 | * @since JDK1.1 |
| 34 | */ |
| 35 | |
| 36 | public class StringReader extends Reader { |
| 37 | |
| 38 | private String str; |
| 39 | private int length; |
| 40 | private int next = 0; |
| 41 | private int mark = 0; |
| 42 | |
| 43 | /** |
| 44 | * Creates a new string reader. |
| 45 | * |
| 46 | * @param s String providing the character stream. |
| 47 | */ |
| 48 | public StringReader(String s) { |
| 49 | this.str = s; |
| 50 | this.length = s.length(); |
| 51 | } |
| 52 | |
| 53 | /** Check to make sure that the stream has not been closed */ |
| 54 | private void ensureOpen() throws IOException { |
| 55 | if (str == null) |
| 56 | throw new IOException("Stream closed"); |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Reads a single character. |
| 61 | * |
| 62 | * @return The character read, or -1 if the end of the stream has been |
| 63 | * reached |
| 64 | * |
| 65 | * @exception IOException If an I/O error occurs |
| 66 | */ |
| 67 | public int read() throws IOException { |
| 68 | synchronized (lock) { |
| 69 | ensureOpen(); |
| 70 | if (next >= length) |
| 71 | return -1; |
| 72 | return str.charAt(next++); |
| 73 | } |
| 74 | } |
| 75 | |
| 76 | /** |
| 77 | * Reads characters into a portion of an array. |
| 78 | * |
| 79 | * @param cbuf Destination buffer |
| 80 | * @param off Offset at which to start writing characters |
| 81 | * @param len Maximum number of characters to read |
| 82 | * |
| 83 | * @return The number of characters read, or -1 if the end of the |
| 84 | * stream has been reached |
| 85 | * |
| 86 | * @exception IOException If an I/O error occurs |
| 87 | */ |
| 88 | public int read(char cbuf[], int off, int len) throws IOException { |
| 89 | synchronized (lock) { |
| 90 | ensureOpen(); |
| 91 | if ((off < 0) || (off > cbuf.length) || (len < 0) || |
| 92 | ((off + len) > cbuf.length) || ((off + len) < 0)) { |
| 93 | throw new IndexOutOfBoundsException(); |
| 94 | } else if (len == 0) { |
| 95 | return 0; |
| 96 | } |
| 97 | if (next >= length) |
| 98 | return -1; |
| 99 | int n = Math.min(length - next, len); |
| 100 | str.getChars(next, next + n, cbuf, off); |
| 101 | next += n; |
| 102 | return n; |
| 103 | } |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * Skips the specified number of characters in the stream. Returns |
| 108 | * the number of characters that were skipped. |
| 109 | * |
| 110 | * <p>The <code>ns</code> parameter may be negative, even though the |
| 111 | * <code>skip</code> method of the {@link Reader} superclass throws |
| 112 | * an exception in this case. Negative values of <code>ns</code> cause the |
| 113 | * stream to skip backwards. Negative return values indicate a skip |
| 114 | * backwards. It is not possible to skip backwards past the beginning of |
| 115 | * the string. |
| 116 | * |
| 117 | * <p>If the entire string has been read or skipped, then this method has |
| 118 | * no effect and always returns 0. |
| 119 | * |
| 120 | * @exception IOException If an I/O error occurs |
| 121 | */ |
| 122 | public long skip(long ns) throws IOException { |
| 123 | synchronized (lock) { |
| 124 | ensureOpen(); |
| 125 | if (next >= length) |
| 126 | return 0; |
| 127 | // Bound skip by beginning and end of the source |
| 128 | long n = Math.min(length - next, ns); |
| 129 | n = Math.max(-next, n); |
| 130 | next += n; |
| 131 | return n; |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | /** |
| 136 | * Tells whether this stream is ready to be read. |
| 137 | * |
| 138 | * @return True if the next read() is guaranteed not to block for input |
| 139 | * |
| 140 | * @exception IOException If the stream is closed |
| 141 | */ |
| 142 | public boolean ready() throws IOException { |
| 143 | synchronized (lock) { |
| 144 | ensureOpen(); |
| 145 | return true; |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | /** |
| 150 | * Tells whether this stream supports the mark() operation, which it does. |
| 151 | */ |
| 152 | public boolean markSupported() { |
| 153 | return true; |
| 154 | } |
| 155 | |
| 156 | /** |
| 157 | * Marks the present position in the stream. Subsequent calls to reset() |
| 158 | * will reposition the stream to this point. |
| 159 | * |
| 160 | * @param readAheadLimit Limit on the number of characters that may be |
| 161 | * read while still preserving the mark. Because |
| 162 | * the stream's input comes from a string, there |
| 163 | * is no actual limit, so this argument must not |
| 164 | * be negative, but is otherwise ignored. |
| 165 | * |
| 166 | * @exception IllegalArgumentException If readAheadLimit is < 0 |
| 167 | * @exception IOException If an I/O error occurs |
| 168 | */ |
| 169 | public void mark(int readAheadLimit) throws IOException { |
| 170 | if (readAheadLimit < 0){ |
| 171 | throw new IllegalArgumentException("Read-ahead limit < 0"); |
| 172 | } |
| 173 | synchronized (lock) { |
| 174 | ensureOpen(); |
| 175 | mark = next; |
| 176 | } |
| 177 | } |
| 178 | |
| 179 | /** |
| 180 | * Resets the stream to the most recent mark, or to the beginning of the |
| 181 | * string if it has never been marked. |
| 182 | * |
| 183 | * @exception IOException If an I/O error occurs |
| 184 | */ |
| 185 | public void reset() throws IOException { |
| 186 | synchronized (lock) { |
| 187 | ensureOpen(); |
| 188 | next = mark; |
| 189 | } |
| 190 | } |
| 191 | |
| 192 | /** |
| 193 | * Closes the stream and releases any system resources associated with |
| 194 | * it. Once the stream has been closed, further read(), |
| 195 | * ready(), mark(), or reset() invocations will throw an IOException. |
| 196 | * Closing a previously closed stream has no effect. |
| 197 | */ |
| 198 | public void close() { |
| 199 | str = null; |
| 200 | } |
| 201 | } |