001/* CharArrayReader.java -- Read an array of characters as a stream 002 Copyright (C) 1998, 2001, 2005 Free Software Foundation, Inc. 003 004This file is part of GNU Classpath. 005 006GNU Classpath is free software; you can redistribute it and/or modify 007it under the terms of the GNU General Public License as published by 008the Free Software Foundation; either version 2, or (at your option) 009any later version. 010 011GNU Classpath is distributed in the hope that it will be useful, but 012WITHOUT ANY WARRANTY; without even the implied warranty of 013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014General Public License for more details. 015 016You should have received a copy of the GNU General Public License 017along with GNU Classpath; see the file COPYING. If not, write to the 018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 01902110-1301 USA. 020 021Linking this library statically or dynamically with other modules is 022making a combined work based on this library. Thus, the terms and 023conditions of the GNU General Public License cover the whole 024combination. 025 026As a special exception, the copyright holders of this library give you 027permission to link this library with independent modules to produce an 028executable, regardless of the license terms of these independent 029modules, and to copy and distribute the resulting executable under 030terms of your choice, provided that you also meet, for each linked 031independent module, the terms and conditions of the license of that 032module. An independent module is a module which is not derived from 033or based on this library. If you modify this library, you may extend 034this exception to your version of the library, but you are not 035obligated to do so. If you do not wish to do so, delete this 036exception statement from your version. */ 037 038 039package java.io; 040 041/** 042 * This class permits an array of chars to be read as an input stream. 043 * 044 * @author Aaron M. Renn (arenn@urbanophile.com) 045 * @author Warren Levy (warrenl@cygnus.com) 046 */ 047public class CharArrayReader extends Reader 048{ 049 /** 050 * The array that contains the data supplied during read operations 051 */ 052 protected char[] buf; 053 054 /** 055 * The array index of the next char to be read from the buffer 056 * <code>buf</code> 057 */ 058 protected int pos; 059 060 /** 061 * The currently marked position in the stream. This defaults to 0, so a 062 * reset operation on the stream resets it to read from array index 0 in 063 * the buffer - even if the stream was initially created with an offset 064 * greater than 0 065 */ 066 protected int markedPos; 067 068 /** 069 * This indicates the maximum number of chars that can be read from this 070 * stream. It is the array index of the position after the last valid 071 * char in the buffer <code>buf</code> 072 */ 073 protected int count; 074 075 /** 076 * Create a new CharArrayReader that will read chars from the passed 077 * in char array. This stream will read from the beginning to the end 078 * of the array. It is identical to calling an overloaded constructor 079 * as <code>CharArrayReader(buf, 0, buf.length)</code>. 080 * <p> 081 * Note that this array is not copied. If its contents are changed 082 * while this stream is being read, those changes will be reflected in the 083 * chars supplied to the reader. Please use caution in changing the 084 * contents of the buffer while this stream is open. 085 * 086 * @param buffer The char array buffer this stream will read from. 087 */ 088 public CharArrayReader(char[] buffer) 089 { 090 this(buffer, 0, buffer.length); 091 } 092 093 /** 094 * Create a new CharArrayReader that will read chars from the passed 095 * in char array. This stream will read from position 096 * <code>offset</code> in the array for a length of 097 * <code>length</code> chars past <code>offset</code>. If the 098 * stream is reset to a position before <code>offset</code> then 099 * more than <code>length</code> chars can be read from the stream. 100 * The <code>length</code> value should be viewed as the array index 101 * one greater than the last position in the buffer to read. 102 * <p> 103 * Note that this array is not copied. If its contents are changed 104 * while this stream is being read, those changes will be reflected in the 105 * chars supplied to the reader. Please use caution in changing the 106 * contents of the buffer while this stream is open. 107 * 108 * @param buffer The char array buffer this stream will read from. 109 * @param offset The index into the buffer to start reading chars from 110 * @param length The number of chars to read from the buffer 111 */ 112 public CharArrayReader(char[] buffer, int offset, int length) 113 { 114 super(); 115 if (offset < 0 || length < 0 || offset > buffer.length) 116 throw new IllegalArgumentException(); 117 118 buf = buffer; 119 120 count = offset + length; 121 if (count > buf.length) 122 count = buf.length; 123 124 pos = offset; 125 markedPos = pos; 126 } 127 128 /** 129 * This method closes the stream. 130 */ 131 public void close() 132 { 133 synchronized (lock) 134 { 135 buf = null; 136 } 137 } 138 139 /** 140 * This method sets the mark position in this stream to the current 141 * position. Note that the <code>readlimit</code> parameter in this 142 * method does nothing as this stream is always capable of 143 * remembering all the chars int it. 144 * <p> 145 * Note that in this class the mark position is set by default to 146 * position 0 in the stream. This is in constrast to some other 147 * stream types where there is no default mark position. 148 * 149 * @param readAheadLimit The number of chars this stream must 150 * remember. This parameter is ignored. 151 * 152 * @exception IOException If an error occurs 153 */ 154 public void mark(int readAheadLimit) throws IOException 155 { 156 synchronized (lock) 157 { 158 if (buf == null) 159 throw new IOException("Stream closed"); 160 // readAheadLimit is ignored per Java Class Lib. book, p. 318. 161 markedPos = pos; 162 } 163 } 164 165 /** 166 * This method overrides the <code>markSupported</code> method in 167 * <code>Reader</code> in order to return <code>true</code> - 168 * indicating that this stream class supports mark/reset 169 * functionality. 170 * 171 * @return <code>true</code> to indicate that this class supports 172 * mark/reset. 173 */ 174 public boolean markSupported() 175 { 176 return true; 177 } 178 179 /** 180 * This method reads one char from the stream. The <code>pos</code> 181 * counter is advanced to the next char to be read. The char read 182 * is returned as an int in the range of 0-65535. If the stream 183 * position is already at the end of the buffer, no char is read and 184 * a -1 is returned in order to indicate the end of the stream. 185 * 186 * @return The char read, or -1 if end of stream 187 */ 188 public int read() throws IOException 189 { 190 synchronized (lock) 191 { 192 if (buf == null) 193 throw new IOException("Stream closed"); 194 195 if (pos < 0) 196 throw new ArrayIndexOutOfBoundsException(pos); 197 198 if (pos < count) 199 return ((int) buf[pos++]) & 0xFFFF; 200 return -1; 201 } 202 } 203 204 /** 205 * This method reads chars from the stream and stores them into a 206 * caller supplied buffer. It starts storing the data at index 207 * <code>offset</code> into the buffer and attempts to read 208 * <code>len</code> chars. This method can return before reading 209 * the number of chars requested if the end of the stream is 210 * encountered first. The actual number of chars read is returned. 211 * If no chars can be read because the stream is already at the end 212 * of stream position, a -1 is returned. 213 * <p> 214 * This method does not block. 215 * 216 * @param b The array into which the chars read should be stored. 217 * @param off The offset into the array to start storing chars 218 * @param len The requested number of chars to read 219 * 220 * @return The actual number of chars read, or -1 if end of stream. 221 */ 222 public int read(char[] b, int off, int len) throws IOException 223 { 224 synchronized (lock) 225 { 226 if (buf == null) 227 throw new IOException("Stream closed"); 228 229 /* Don't need to check pos value, arraycopy will check it. */ 230 if (off < 0 || len < 0 || off + len > b.length) 231 throw new IndexOutOfBoundsException(); 232 233 if (pos >= count) 234 return -1; 235 236 int numChars = Math.min(count - pos, len); 237 System.arraycopy(buf, pos, b, off, numChars); 238 pos += numChars; 239 return numChars; 240 } 241 } 242 243 /** 244 * Return true if more characters are available to be read. 245 * 246 * @return <code>true</code> to indicate that this stream is ready 247 * to be read. 248 * 249 * @specnote The JDK 1.3 API docs are wrong here. This method will 250 * return false if there are no more characters available. 251 */ 252 public boolean ready() throws IOException 253 { 254 if (buf == null) 255 throw new IOException("Stream closed"); 256 257 return (pos < count); 258 } 259 260 /** 261 * This method sets the read position in the stream to the mark 262 * point by setting the <code>pos</code> variable equal to the 263 * <code>mark</code> variable. Since a mark can be set anywhere in 264 * the array, the mark/reset methods int this class can be used to 265 * provide random search capabilities for this type of stream. 266 */ 267 public void reset() throws IOException 268 { 269 synchronized (lock) 270 { 271 if (buf == null) 272 throw new IOException("Stream closed"); 273 274 pos = markedPos; 275 } 276 } 277 278 /** 279 * This method attempts to skip the requested number of chars in the 280 * input stream. It does this by advancing the <code>pos</code> value by the 281 * specified number of chars. It this would exceed the length of the 282 * buffer, then only enough chars are skipped to position the stream at 283 * the end of the buffer. The actual number of chars skipped is returned. 284 * 285 * @param n The requested number of chars to skip 286 * 287 * @return The actual number of chars skipped. 288 */ 289 public long skip(long n) throws IOException 290 { 291 synchronized (lock) 292 { 293 if (buf == null) 294 throw new IOException("Stream closed"); 295 296 // Even though the var numChars is a long, in reality it can never 297 // be larger than an int since the result of subtracting 2 positive 298 // ints will always fit in an int. Since we have to return a long 299 // anyway, numChars might as well just be a long. 300 long numChars = Math.min((long) (count - pos), n < 0 ? 0L : n); 301 pos += numChars; 302 return numChars; 303 } 304 } 305}