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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    * 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   }

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