bufferedreader.java

This is a resource based on j2me embedded,if you dont understand,you can connection with me .

/*
 * @(#)BufferedReader.java	1.35 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * This program 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 at /legal/license.txt).   
 *   
 * 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 Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.io;


/**
 * Read text from a character-input stream, buffering characters so as to
 * provide for the efficient reading of characters, arrays, and lines.
 *
 * <p> The buffer size may be specified, or the default size may be used.  The
 * default is large enough for most purposes.
 *
 * <p> In general, each read request made of a Reader causes a corresponding
 * read request to be made of the underlying character or byte stream.  It is
 * therefore advisable to wrap a BufferedReader around any Reader whose read()
 * operations may be costly, such as FileReaders and InputStreamReaders.  For
 * example,
 *
 * <pre>
 * BufferedReader in
 *   = new BufferedReader(new FileReader("foo.in"));
 * </pre>
 *
 * will buffer the input from the specified file.  Without buffering, each
 * invocation of read() or readLine() could cause bytes to be read from the
 * file, converted into characters, and then returned, which can be very
 * inefficient. 
 *
 * <p> Programs that use DataInputStreams for textual input can be localized by
 * replacing each DataInputStream with an appropriate BufferedReader.
 *
 * @see FileReader
 * @see InputStreamReader
 *
 * @version 	1.29 10/10/01
 * @author	Mark Reinhold
 * @since	JDK1.1
 */

public class BufferedReader extends Reader {

    private Reader in;

    private char cb[];
    private int nChars, nextChar;

    private static final int INVALIDATED = -2;
    private static final int UNMARKED = -1;
    private int markedChar = UNMARKED;
    private int readAheadLimit = 0; /* Valid only when markedChar > 0 */

    /** If the next character is a line feed, skip it */
    private boolean skipLF = false;

    /** The skipLF flag when the mark was set */
    private boolean markedSkipLF = false;

    private static int defaultCharBufferSize = 8192;
    private static int defaultExpectedLineLength = 80;

    /**
     * Create a buffering character-input stream that uses an input buffer of
     * the specified size.
     *
     * @param  in   A Reader
     * @param  sz   Input-buffer size
     *
     * @exception  IllegalArgumentException  If sz is <= 0
     */
    public BufferedReader(Reader in, int sz) {
	super(in);
	if (sz <= 0)
	    throw new IllegalArgumentException("Buffer size <= 0");
	this.in = in;
	cb = new char[sz];
	nextChar = nChars = 0;
    }

    /**
     * Create a buffering character-input stream that uses a default-sized
     * input buffer.
     *
     * @param  in   A Reader
     */
    public BufferedReader(Reader in) {
	this(in, defaultCharBufferSize);
    }

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

    /**
     * Fill the input buffer, taking the mark into account if it is valid.
     */
    private void fill() throws IOException {
	int dst;
	if (markedChar <= UNMARKED) {
	    /* No mark */
	    dst = 0;
	} else {
	    /* Marked */
	    int delta = nextChar - markedChar;
	    if (delta >= readAheadLimit) {
		/* Gone past read-ahead limit: Invalidate mark */
		markedChar = INVALIDATED;
		readAheadLimit = 0;
		dst = 0;
	    } else {
		if (readAheadLimit <= cb.length) {
		    /* Shuffle in the current buffer */
		    System.arraycopy(cb, markedChar, cb, 0, delta);
		    markedChar = 0;
		    dst = delta;
		} else {
		    /* Reallocate buffer to accomodate read-ahead limit */
		    char ncb[] = new char[readAheadLimit];
		    System.arraycopy(cb, markedChar, ncb, 0, delta);
		    cb = ncb;
		    markedChar = 0;
		    dst = delta;
		}
                nextChar = nChars = delta;
	    }
	}

	int n;
	do {
	    n = in.read(cb, dst, cb.length - dst);
	} while (n == 0);
	if (n > 0) {
	    nChars = dst + n;
	    nextChar = dst;
	}
    }

    /**
     * Read a single character.
     *
     * @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 {
	synchronized (lock) {
	    ensureOpen();
	    for (;;) {
		if (nextChar >= nChars) {
		    fill();
		    if (nextChar >= nChars)
			return -1;
		}
		if (skipLF) {
		    skipLF = false;
		    if (cb[nextChar] == '\n') {
			nextChar++;
			continue;
		    }
		}
		return cb[nextChar++];
	    }
	}
    }

    /**
     * Read characters into a portion of an array, reading from the underlying
     * stream if necessary.
     */
    private int read1(char[] cbuf, int off, int len) throws IOException {
	if (nextChar >= nChars) {
	    /* If the requested length is at least as large as the buffer, and
	       if there is no mark/reset activity, and if line feeds are not
	       being skipped, do not bother to copy the characters into the
	       local buffer.  In this way buffered streams will cascade
	       harmlessly. */
	    if (len >= cb.length && markedChar <= UNMARKED && !skipLF) {
		return in.read(cbuf, off, len);
	    }
	    fill();
	}
	if (nextChar >= nChars) return -1;
	if (skipLF) {
	    skipLF = false;
	    if (cb[nextChar] == '\n') {
		nextChar++;
		if (nextChar >= nChars)
		    fill();
		if (nextChar >= nChars)
		    return -1;
	    }
	}
	int n = Math.min(len, nChars - nextChar);
	System.arraycopy(cb, nextChar, cbuf, off, n);
	nextChar += n;
	return n;
    }

    /**
     * Read characters into a portion of an array.
     *
     * <p> This method implements the general contract of the corresponding
     * <code>{@link Reader#read(char[], int, int) read}</code> method of the
     * <code>{@link Reader}</code> class.  As an additional convenience, it
     * attempts to read as many characters as possible by repeatedly invoking
     * the <code>read</code> method of the underlying stream.  This iterated
     * <code>read</code> continues until one of the following conditions becomes
     * true: <ul>
     *
     *   <li> The specified number of characters have been read,
     *
     *   <li> The <code>read</code> method of the underlying stream returns
     *   <code>-1</code>, indicating end-of-file, or
     *
     *   <li> The <code>ready</code> method of the underlying stream
     *   returns <code>false</code>, indicating that further input requests
     *   would block.
     *
     * </ul> If the first <code>read</code> on the underlying stream returns
     * <code>-1</code> to indicate end-of-file then this method returns
     * <code>-1</code>.  Otherwise this method returns the number of characters
     * actually read.
     *
     * <p> Subclasses of this class are encouraged, but not required, to
     * attempt to read as many characters as possible in the same fashion.
     *
     * <p> Ordinarily this method takes characters from this stream's character
     * buffer, filling it from the underlying stream as necessary.  If,
     * however, the buffer is empty, the mark is not valid, and the requested
     * length is at least as large as the buffer, then this method will read
     * characters directly from the underlying stream into the given array.
     * Thus redundant <code>BufferedReader</code>s will not copy data
     * unnecessarily.
     *
     * @param      cbuf  Destination buffer
     * @param      off   Offset at which to start storing characters
     * @param      len   Maximum number of characters to read
     *