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 // BEGIN Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow. 134 int avail = count - pos; 135 if (len > avail) { 136 len = avail; 137 } 138 // END Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow. 139 if (len <= 0) { 140 return 0; 141 } 142 System.arraycopy(buf, pos, b, off, len); 143 pos += len; 144 return len; 145 } 146 } 147 148 /** 149 * Skips characters. Returns the number of characters that were skipped. 150 * 151 * <p>The <code>n</code> parameter may be negative, even though the 152 * <code>skip</code> method of the {@link Reader} superclass throws 153 * an exception in this case. If <code>n</code> is negative, then 154 * this method does nothing and returns <code>0</code>. 155 * 156 * @param n The number of characters to skip 157 * @return The number of characters actually skipped 158 * @exception IOException If the stream is closed, or an I/O error occurs 159 */ 160 public long skip(long n) throws IOException { 161 synchronized (lock) { 162 ensureOpen(); 163 // BEGIN Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow. 164 long avail = count - pos; 165 if (n > avail) { 166 n = avail; 167 } 168 // END Android-changed: Backport of OpenJDK 9b132 fix to avoid integer overflow. 169 if (n < 0) { 170 return 0; 171 } 172 pos += n; 173 return n; 174 } 175 } 176 177 /** 178 * Tells whether this stream is ready to be read. Character-array readers 179 * are always ready to be read. 180 * 181 * @exception IOException If an I/O error occurs 182 */ 183 public boolean ready() throws IOException { 184 synchronized (lock) { 185 ensureOpen(); 186 return (count - pos) > 0; 187 } 188 } 189 190 /** 191 * Tells whether this stream supports the mark() operation, which it does. 192 */ 193 public boolean markSupported() { 194 return true; 195 } 196 197 /** 198 * Marks the present position in the stream. Subsequent calls to reset() 199 * will reposition the stream to this point. 200 * 201 * @param readAheadLimit Limit on the number of characters that may be 202 * read while still preserving the mark. Because 203 * the stream's input comes from a character array, 204 * there is no actual limit; hence this argument is 205 * ignored. 206 * 207 * @exception IOException If an I/O error occurs 208 */ 209 public void mark(int readAheadLimit) throws IOException { 210 synchronized (lock) { 211 ensureOpen(); 212 markedPos = pos; 213 } 214 } 215 216 /** 217 * Resets the stream to the most recent mark, or to the beginning if it has 218 * never been marked. 219 * 220 * @exception IOException If an I/O error occurs 221 */ 222 public void reset() throws IOException { 223 synchronized (lock) { 224 ensureOpen(); 225 pos = markedPos; 226 } 227 } 228 229 /** 230 * Closes the stream and releases any system resources associated with 231 * it. Once the stream has been closed, further read(), ready(), 232 * mark(), reset(), or skip() invocations will throw an IOException. 233 * Closing a previously closed stream has no effect. 234 */ 235 public void close() { 236 buf = null; 237 } 238 } 239
