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jeremybenn |
/* CharArrayReader.java -- Read an array of characters as a stream
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Copyright (C) 1998, 2001, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.io;
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/**
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* This class permits an array of chars to be read as an input stream.
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*
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @author Warren Levy (warrenl@cygnus.com)
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*/
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public class CharArrayReader extends Reader
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{
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/**
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* The array that contains the data supplied during read operations
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*/
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protected char[] buf;
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/**
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* The array index of the next char to be read from the buffer
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* <code>buf</code>
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*/
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protected int pos;
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/**
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* The currently marked position in the stream. This defaults to 0, so a
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* reset operation on the stream resets it to read from array index 0 in
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* the buffer - even if the stream was initially created with an offset
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* greater than 0
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*/
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protected int markedPos;
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/**
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* This indicates the maximum number of chars that can be read from this
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* stream. It is the array index of the position after the last valid
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* char in the buffer <code>buf</code>
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*/
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protected int count;
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/**
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* Create a new CharArrayReader that will read chars from the passed
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* in char array. This stream will read from the beginning to the end
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* of the array. It is identical to calling an overloaded constructor
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* as <code>CharArrayReader(buf, 0, buf.length)</code>.
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* <p>
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* Note that this array is not copied. If its contents are changed
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* while this stream is being read, those changes will be reflected in the
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* chars supplied to the reader. Please use caution in changing the
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* contents of the buffer while this stream is open.
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*
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* @param buffer The char array buffer this stream will read from.
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*/
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public CharArrayReader(char[] buffer)
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{
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this(buffer, 0, buffer.length);
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}
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/**
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* Create a new CharArrayReader that will read chars from the passed
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* in char array. This stream will read from position
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* <code>offset</code> in the array for a length of
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* <code>length</code> chars past <code>offset</code>. If the
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* stream is reset to a position before <code>offset</code> then
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* more than <code>length</code> chars can be read from the stream.
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* The <code>length</code> value should be viewed as the array index
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* one greater than the last position in the buffer to read.
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* <p>
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* Note that this array is not copied. If its contents are changed
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* while this stream is being read, those changes will be reflected in the
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* chars supplied to the reader. Please use caution in changing the
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* contents of the buffer while this stream is open.
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*
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* @param buffer The char array buffer this stream will read from.
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* @param offset The index into the buffer to start reading chars from
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* @param length The number of chars to read from the buffer
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*/
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public CharArrayReader(char[] buffer, int offset, int length)
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{
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super();
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if (offset < 0 || length < 0 || offset > buffer.length)
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throw new IllegalArgumentException();
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buf = buffer;
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count = offset + length;
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if (count > buf.length)
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count = buf.length;
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pos = offset;
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markedPos = pos;
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}
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/**
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* This method closes the stream.
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*/
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public void close()
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{
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synchronized (lock)
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{
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buf = null;
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}
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}
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/**
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* This method sets the mark position in this stream to the current
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* position. Note that the <code>readlimit</code> parameter in this
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* method does nothing as this stream is always capable of
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* remembering all the chars int it.
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* <p>
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* Note that in this class the mark position is set by default to
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* position 0 in the stream. This is in constrast to some other
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* stream types where there is no default mark position.
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*
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* @param readAheadLimit The number of chars this stream must
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* remember. This parameter is ignored.
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*
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* @exception IOException If an error occurs
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*/
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public void mark(int readAheadLimit) throws IOException
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{
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synchronized (lock)
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{
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if (buf == null)
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throw new IOException("Stream closed");
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// readAheadLimit is ignored per Java Class Lib. book, p. 318.
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markedPos = pos;
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}
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}
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/**
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* This method overrides the <code>markSupported</code> method in
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* <code>Reader</code> in order to return <code>true</code> -
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* indicating that this stream class supports mark/reset
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* functionality.
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*
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* @return <code>true</code> to indicate that this class supports
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* mark/reset.
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*/
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public boolean markSupported()
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{
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return true;
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}
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/**
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* This method reads one char from the stream. The <code>pos</code>
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* counter is advanced to the next char to be read. The char read
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* is returned as an int in the range of 0-65535. If the stream
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* position is already at the end of the buffer, no char is read and
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* a -1 is returned in order to indicate the end of the stream.
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*
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* @return The char read, or -1 if end of stream
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*/
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public int read() throws IOException
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{
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synchronized (lock)
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{
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if (buf == null)
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throw new IOException("Stream closed");
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if (pos < 0)
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throw new ArrayIndexOutOfBoundsException(pos);
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if (pos < count)
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return ((int) buf[pos++]) & 0xFFFF;
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return -1;
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}
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}
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/**
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* This method reads chars from the stream and stores them into a
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* caller supplied buffer. It starts storing the data at index
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* <code>offset</code> into the buffer and attempts to read
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* <code>len</code> chars. This method can return before reading
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* the number of chars requested if the end of the stream is
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* encountered first. The actual number of chars read is returned.
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* If no chars can be read because the stream is already at the end
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* of stream position, a -1 is returned.
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* <p>
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* This method does not block.
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*
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* @param b The array into which the chars read should be stored.
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* @param off The offset into the array to start storing chars
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* @param len The requested number of chars to read
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*
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* @return The actual number of chars read, or -1 if end of stream.
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*/
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public int read(char[] b, int off, int len) throws IOException
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{
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synchronized (lock)
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{
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if (buf == null)
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throw new IOException("Stream closed");
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/* Don't need to check pos value, arraycopy will check it. */
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if (off < 0 || len < 0 || off + len > b.length)
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throw new IndexOutOfBoundsException();
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if (pos >= count)
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return -1;
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int numChars = Math.min(count - pos, len);
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System.arraycopy(buf, pos, b, off, numChars);
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pos += numChars;
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return numChars;
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}
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}
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/**
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* Return true if more characters are available to be read.
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*
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* @return <code>true</code> to indicate that this stream is ready
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* to be read.
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*
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* @specnote The JDK 1.3 API docs are wrong here. This method will
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* return false if there are no more characters available.
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*/
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public boolean ready() throws IOException
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{
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if (buf == null)
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throw new IOException("Stream closed");
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return (pos < count);
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}
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/**
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* This method sets the read position in the stream to the mark
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* point by setting the <code>pos</code> variable equal to the
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* <code>mark</code> variable. Since a mark can be set anywhere in
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* the array, the mark/reset methods int this class can be used to
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* provide random search capabilities for this type of stream.
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*/
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public void reset() throws IOException
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{
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synchronized (lock)
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{
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if (buf == null)
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throw new IOException("Stream closed");
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pos = markedPos;
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}
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}
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/**
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* This method attempts to skip the requested number of chars in the
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* input stream. It does this by advancing the <code>pos</code> value by the
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* specified number of chars. It this would exceed the length of the
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* buffer, then only enough chars are skipped to position the stream at
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* the end of the buffer. The actual number of chars skipped is returned.
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*
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* @param n The requested number of chars to skip
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*
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* @return The actual number of chars skipped.
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*/
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public long skip(long n) throws IOException
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{
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synchronized (lock)
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{
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if (buf == null)
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throw new IOException("Stream closed");
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// Even though the var numChars is a long, in reality it can never
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// be larger than an int since the result of subtracting 2 positive
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// ints will always fit in an int. Since we have to return a long
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// anyway, numChars might as well just be a long.
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long numChars = Math.min((long) (count - pos), n < 0 ? 0L : n);
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pos += numChars;
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return numChars;
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}
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}
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}
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