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| 1 | +/* | |
| 2 | + * Copyright (c) 1996, 2005, 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 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 | +} | |