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	/*
	* Copyright (c) 1996, 2012, 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;


	/**
	* Abstract class for reading character streams. The only methods that a
	* subclass must implement are read(char[], int, int) and close(). Most
	* subclasses, however, will override some of the methods defined here in order
	* to provide higher efficiency, additional functionality, or both.
	*
	*
	* @see BufferedReader
	* @see LineNumberReader
	* @see CharArrayReader
	* @see InputStreamReader
	* @see FileReader
	* @see FilterReader
	* @see PushbackReader
	* @see PipedReader
	* @see StringReader
	* @see Writer
	*
	* @author Mark Reinhold
	* @since JDK1.1
	*/

	public abstract class Reader implements Readable, Closeable {

	/**
	* The object used to synchronize operations on this stream. For
	* efficiency, a character-stream object may use an object other than
	* itself to protect critical sections. A subclass should therefore use
	* the object in this field rather than <tt>this</tt> or a synchronized
	* method.
	*/
	protected Object lock;

	/**
	* Creates a new character-stream reader whose critical sections will
	* synchronize on the reader itself.
	*/
	protected Reader() {
	this.lock = this;
	}

	/**
	* Creates a new character-stream reader whose critical sections will
	* synchronize on the given object.
	*
	* @param lock The Object to synchronize on.
	*/
	protected Reader(Object lock) {
	if (lock == null) {
	throw new NullPointerException();
	}
	this.lock = lock;
	}

	/**
	* Attempts to read characters into the specified character buffer.
	* The buffer is used as a repository of characters as-is: the only
	* changes made are the results of a put operation. No flipping or
	* rewinding of the buffer is performed.
	*
	* @param target the buffer to read characters into
	* @return The number of characters added to the buffer, or
	* -1 if this source of characters is at its end
	* @throws IOException if an I/O error occurs
	* @throws NullPointerException if target is null
	* @throws java.nio.ReadOnlyBufferException if target is a read only buffer
	* @since 1.5
	*/
	public int read(java.nio.CharBuffer target) throws IOException {
	int len = target.remaining();
	char[] cbuf = new char[len];
	int n = read(cbuf, 0, len);
	if (n > 0)
	target.put(cbuf, 0, n);
	return n;
	}

	/**
	* Reads a single character. This method will block until a character is
	* available, an I/O error occurs, or the end of the stream is reached.
	*
	* <p> Subclasses that intend to support efficient single-character input
	* should override this method.
	*
	* @return The character read, as an integer in the range 0 to 65535
	* (<tt>0x00-0xffff</tt>), or -1 if the end of the stream has
	* been reached
	*
	* @exception IOException If an I/O error occurs
	*/
	public int read() throws IOException {
	char cb[] = new char[1];
	if (read(cb, 0, 1) == -1)
	return -1;
	else
	return cb[0];
	}

	/**
	* Reads characters into an array. This method will block until some input
	* is available, an I/O error occurs, or the end of the stream is reached.
	*
	* @param cbuf Destination buffer
	*
	* @return The 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 cbuf[]) throws IOException {
	return read(cbuf, 0, cbuf.length);
	}

	/**
	* Reads characters into a portion of an array. This method will block
	* until some input is available, an I/O error occurs, or the end of the
	* stream is reached.
	*
	* @param cbuf Destination buffer
	* @param off Offset at which to start storing characters
	* @param len Maximum number of characters to read
	*
	* @return The number of characters read, or -1 if the end of the
	* stream has been reached
	*
	* @exception IOException If an I/O error occurs
	*/
	abstract public int read(char cbuf[], int off, int len) throws IOException;

	/** Maximum skip-buffer size */
	private static final int maxSkipBufferSize = 8192;

	/** Skip buffer, null until allocated */
	private char skipBuffer[] = null;

	/**
	* Skips characters. This method will block until some characters are
	* available, an I/O error occurs, or the end of the stream is reached.
	*
	* @param n The number of characters to skip
	*
	* @return The number of characters actually skipped
	*
	* @exception IllegalArgumentException If <code>n</code> is negative.
	* @exception IOException If an I/O error occurs
	*/
	public long skip(long n) throws IOException {
	if (n < 0L)
	throw new IllegalArgumentException("skip value is negative");
	int nn = (int) Math.min(n, maxSkipBufferSize);
	synchronized (lock) {
	if ((skipBuffer == null) \|\| (skipBuffer.length < nn))
	skipBuffer = new char[nn];
	long r = n;
	while (r > 0) {
	int nc = read(skipBuffer, 0, (int)Math.min(r, nn));
	if (nc == -1)
	break;
	r -= nc;
	}
	return n - r;
	}
	}

	/**
	* Tells whether this stream is ready to be read.
	*
	* @return True if the next read() is guaranteed not to block for input,
	* false otherwise. Note that returning false does not guarantee that the
	* next read will block.
	*
	* @exception IOException If an I/O error occurs
	*/
	public boolean ready() throws IOException {
	return false;
	}

	/**
	* Tells whether this stream supports the mark() operation. The default
	* implementation always returns false. Subclasses should override this
	* method.
	*
	* @return true if and only if this stream supports the mark operation.
	*/
	public boolean markSupported() {
	return false;
	}

	/**
	* Marks the present position in the stream. Subsequent calls to reset()
	* will attempt to reposition the stream to this point. Not all
	* character-input streams support the mark() operation.
	*
	* @param readAheadLimit Limit on the number of characters that may be
	* read while still preserving the mark. After
	* reading this many characters, attempting to
	* reset the stream may fail.
	*
	* @exception IOException If the stream does not support mark(),
	* or if some other I/O error occurs
	*/
	public void mark(int readAheadLimit) throws IOException {
	throw new IOException("mark() not supported");
	}

	/**
	* Resets the stream. If the stream has been marked, then attempt to
	* reposition it at the mark. If the stream has not been marked, then
	* attempt to reset it in some way appropriate to the particular stream,
	* for example by repositioning it to its starting point. Not all
	* character-input streams support the reset() operation, and some support
	* reset() without supporting mark().
	*
	* @exception IOException If the stream has not been marked,
	* or if the mark has been invalidated,
	* or if the stream does not support reset(),
	* or if some other I/O error occurs
	*/
	public void reset() throws IOException {
	throw new IOException("reset() not supported");
	}

	/**
	* 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.
	*
	* @exception IOException If an I/O error occurs
	*/
	abstract public void close() throws IOException;

	}

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