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 * This class implements a character buffer that can be used as a 30 * character-input stream. 31 * 32 * @author Herb Jellinek 33 * @since JDK1.1 34 */ 35 public class CharArrayReader extends Reader { 36 /** The character buffer. */ 37 protected char buf[]; 38 39 /** The current buffer position. */ 40 protected int pos; 41 42 /** The position of mark in buffer. */ 43 protected int markedPos = 0; 44 45 /** 46 * The index of the end of this buffer. There is not valid 47 * data at or beyond this index. 48 */ 49 protected int count; 50 51 /** 52 * Creates a CharArrayReader from the specified array of chars. 53 * @param buf Input buffer (not copied) 54 */ 55 public CharArrayReader(char buf[]) { 56 this.buf = buf; 57 this.pos = 0; 58 this.count = buf.length; 59 } 60 61 /** 62 * Creates a CharArrayReader from the specified array of chars. 63 * 64 * <p> The resulting reader will start reading at the given 65 * <tt>offset</tt>. The total number of <tt>char</tt> values that can be 66 * read from this reader will be either <tt>length</tt> or 67 * <tt>buf.length-offset</tt>, whichever is smaller. 68 * 69 * @throws IllegalArgumentException 70 * If <tt>offset</tt> is negative or greater than 71 * <tt>buf.length</tt>, or if <tt>length</tt> is negative, or if 72 * the sum of these two values is negative. 73 * 74 * @param buf Input buffer (not copied) 75 * @param offset Offset of the first char to read 76 * @param length Number of chars to read 77 */ 78 public CharArrayReader(char buf[], int offset, int length) { 79 if ((offset < 0) || (offset > buf.length) || (length < 0) || 80 ((offset + length) < 0)) { 81 throw new IllegalArgumentException(); 82 } 83 this.buf = buf; 84 this.pos = offset; 85 this.count = Math.min(offset + length, buf.length); 86 this.markedPos = offset; 87 } 88 89 /** Checks to make sure that the stream has not been closed */ 90 private void ensureOpen() throws IOException { 91 if (buf == null) 92 throw new IOException("Stream closed"); 93 } 94 95 /** 96 * Reads a single character. 97 * 98 * @exception IOException If an I/O error occurs 99 */ 100 public int read() throws IOException { 101 synchronized (lock) { 102 ensureOpen(); 103 if (pos >= count) 104 return -1; 105 else 106 return buf[pos++]; 107 } 108 } 109 110 /** 111 * Reads characters into a portion of an array. 112 * @param b Destination buffer 113 * @param off Offset at which to start storing characters 114 * @param len Maximum number of characters to read 115 * @return The actual number of characters read, or -1 if 116 * the end of the stream has been reached 117 * 118 * @exception IOException If an I/O error occurs 119 */ 120 public int read(char b[], int off, int len) throws IOException { 121 synchronized (lock) { 122 ensureOpen(); 123 if ((off < 0) || (off > b.length) || (len < 0) || 124 ((off + len) > b.length) || ((off + len) < 0)) { 125 throw new IndexOutOfBoundsException(); 126 } else if (len == 0) { 127 return 0; 128 } 129 130 if (pos >= count) { 131 return -1; 132 } 133 if (pos + len > count) { 134 len = count - pos; 135 } 136 if (len <= 0) { 137 return 0; 138 } 139 System.arraycopy(buf, pos, b, off, len); 140 pos += len; 141 return len; 142 } 143 } 144 145 /** 146 * Skips characters. Returns the number of characters that were skipped. 147 * 148 * <p>The <code>n</code> parameter may be negative, even though the 149 * <code>skip</code> method of the {@link Reader} superclass throws 150 * an exception in this case. If <code>n</code> is negative, then 151 * this method does nothing and returns <code>0</code>. 152 * 153 * @param n The number of characters to skip 154 * @return The number of characters actually skipped 155 * @exception IOException If the stream is closed, or an I/O error occurs 156 */ 157 public long skip(long n) throws IOException { 158 synchronized (lock) { 159 ensureOpen(); 160 if (pos + n > count) { 161 n = count - pos; 162 } 163 if (n < 0) { 164 return 0; 165 } 166 pos += n; 167 return n; 168 } 169 } 170 171 /** 172 * Tells whether this stream is ready to be read. Character-array readers 173 * are always ready to be read. 174 * 175 * @exception IOException If an I/O error occurs 176 */ 177 public boolean ready() throws IOException { 178 synchronized (lock) { 179 ensureOpen(); 180 return (count - pos) > 0; 181 } 182 } 183 184 /** 185 * Tells whether this stream supports the mark() operation, which it does. 186 */ 187 public boolean markSupported() { 188 return true; 189 } 190 191 /** 192 * Marks the present position in the stream. Subsequent calls to reset() 193 * will reposition the stream to this point. 194 * 195 * @param readAheadLimit Limit on the number of characters that may be 196 * read while still preserving the mark. Because 197 * the stream's input comes from a character array, 198 * there is no actual limit; hence this argument is 199 * ignored. 200 * 201 * @exception IOException If an I/O error occurs 202 */ 203 public void mark(int readAheadLimit) throws IOException { 204 synchronized (lock) { 205 ensureOpen(); 206 markedPos = pos; 207 } 208 } 209 210 /** 211 * Resets the stream to the most recent mark, or to the beginning if it has 212 * never been marked. 213 * 214 * @exception IOException If an I/O error occurs 215 */ 216 public void reset() throws IOException { 217 synchronized (lock) { 218 ensureOpen(); 219 pos = markedPos; 220 } 221 } 222 223 /** 224 * Closes the stream and releases any system resources associated with 225 * it. Once the stream has been closed, further read(), ready(), 226 * mark(), reset(), or skip() invocations will throw an IOException. 227 * Closing a previously closed stream has no effect. 228 */ 229 public void close() { 230 buf = null; 231 } 232 } 233
