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	/*
	* Copyright (c) 1996, 2005, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.io;

	/**
	* This class implements a character buffer that can be used as a
	* character-input stream.
	*
	* @author Herb Jellinek
	* @since JDK1.1
	*/
	public class CharArrayReader extends Reader {
	/** The character buffer. */
	protected char buf[];

	/** The current buffer position. */
	protected int pos;

	/** The position of mark in buffer. */
	protected int markedPos = 0;

	/**
	* The index of the end of this buffer. There is not valid
	* data at or beyond this index.
	*/
	protected int count;

	/**
	* Creates a CharArrayReader from the specified array of chars.
	* @param buf Input buffer (not copied)
	*/
	public CharArrayReader(char buf[]) {
	this.buf = buf;
	this.pos = 0;
	this.count = buf.length;
	}

	/**
	* Creates a CharArrayReader from the specified array of chars.
	*
	* <p> The resulting reader will start reading at the given
	* <tt>offset</tt>. The total number of <tt>char</tt> values that can be
	* read from this reader will be either <tt>length</tt> or
	* <tt>buf.length-offset</tt>, whichever is smaller.
	*
	* @throws IllegalArgumentException
	* If <tt>offset</tt> is negative or greater than
	* <tt>buf.length</tt>, or if <tt>length</tt> is negative, or if
	* the sum of these two values is negative.
	*
	* @param buf Input buffer (not copied)
	* @param offset Offset of the first char to read
	* @param length Number of chars to read
	*/
	public CharArrayReader(char buf[], int offset, int length) {
	if ((offset < 0) \|\| (offset > buf.length) \|\| (length < 0) \|\|
	((offset + length) < 0)) {
	throw new IllegalArgumentException();
	}
	this.buf = buf;
	this.pos = offset;
	this.count = Math.min(offset + length, buf.length);
	this.markedPos = offset;
	}

	/** Checks to make sure that the stream has not been closed */
	private void ensureOpen() throws IOException {
	if (buf == null)
	throw new IOException("Stream closed");
	}

	/**
	* Reads a single character.
	*
	* @exception IOException If an I/O error occurs
	*/
	public int read() throws IOException {
	synchronized (lock) {
	ensureOpen();
	if (pos >= count)
	return -1;
	else
	return buf[pos++];
	}
	}

	/**
	* Reads characters into a portion of an array.
	* @param b Destination buffer
	* @param off Offset at which to start storing characters
	* @param len Maximum number of characters to read
	* @return The actual number of characters read, or -1 if
	* the end of the stream has been reached
	*
	* @exception IOException If an I/O error occurs
	*/
	public int read(char b[], int off, int len) throws IOException {
	synchronized (lock) {
	ensureOpen();
	if ((off < 0) \|\| (off > b.length) \|\| (len < 0) \|\|
	((off + len) > b.length) \|\| ((off + len) < 0)) {
	throw new IndexOutOfBoundsException();
	} else if (len == 0) {
	return 0;
	}

	if (pos >= count) {
	return -1;
	}

	int avail = count - pos;
	if (len > avail) {
	len = avail;
	}
	if (len <= 0) {
	return 0;
	}
	System.arraycopy(buf, pos, b, off, len);
	pos += len;
	return len;
	}
	}

	/**
	* Skips characters. Returns the number of characters that were skipped.
	*
	* <p>The <code>n</code> parameter may be negative, even though the
	* <code>skip</code> method of the {@link Reader} superclass throws
	* an exception in this case. If <code>n</code> is negative, then
	* this method does nothing and returns <code>0</code>.
	*
	* @param n The number of characters to skip
	* @return The number of characters actually skipped
	* @exception IOException If the stream is closed, or an I/O error occurs
	*/
	public long skip(long n) throws IOException {
	synchronized (lock) {
	ensureOpen();

	long avail = count - pos;
	if (n > avail) {
	n = avail;
	}
	if (n < 0) {
	return 0;
	}
	pos += n;
	return n;
	}
	}

	/**
	* Tells whether this stream is ready to be read. Character-array readers
	* are always ready to be read.
	*
	* @exception IOException If an I/O error occurs
	*/
	public boolean ready() throws IOException {
	synchronized (lock) {
	ensureOpen();
	return (count - pos) > 0;
	}
	}

	/**
	* Tells whether this stream supports the mark() operation, which it does.
	*/
	public boolean markSupported() {
	return true;
	}

	/**
	* Marks the present position in the stream. Subsequent calls to reset()
	* will reposition the stream to this point.
	*
	* @param readAheadLimit Limit on the number of characters that may be
	* read while still preserving the mark. Because
	* the stream's input comes from a character array,
	* there is no actual limit; hence this argument is
	* ignored.
	*
	* @exception IOException If an I/O error occurs
	*/
	public void mark(int readAheadLimit) throws IOException {
	synchronized (lock) {
	ensureOpen();
	markedPos = pos;
	}
	}

	/**
	* Resets the stream to the most recent mark, or to the beginning if it has
	* never been marked.
	*
	* @exception IOException If an I/O error occurs
	*/
	public void reset() throws IOException {
	synchronized (lock) {
	ensureOpen();
	pos = markedPos;
	}
	}

	/**
	* Closes the stream and releases any system resources associated with
	* it. Once the stream has been closed, further read(), ready(),
	* mark(), reset(), or skip() invocations will throw an IOException.
	* Closing a previously closed stream has no effect.
	*/
	public void close() {
	buf = null;
	}
	}

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