Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/io/LineNumberReader.java

Java Source | 1998-03-20 | 5.8 KB | 223 lines

/*
 * @(#)LineNumberReader.java    1.9 98/03/18
 *
 * Copyright 1996-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.io;


/**
 * A buffered character-input stream that keeps track of line numbers.  A line
 * is considered to be terminated by any one of a line feed ('\n'), a carriage
 * return ('\r'), or a carriage return followed immediately by a linefeed.
 *
 * @version     1.9, 98/03/18
 * @author    Mark Reinhold
 * @since    JDK1.1
 */

public class LineNumberReader extends BufferedReader {

    /** The current line number */
    private int lineNumber = 0;

    /** The line number of the mark, if any */
    private int markedLineNumber;

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

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

    /**
     * Create a new line-numbering reader, using the default input-buffer
     * size.
     */
    public LineNumberReader(Reader in) {
    super(in);
    }

    /**
     * Create a new line-numbering reader, reading characters into a buffer of
     * the given size.
     */
    public LineNumberReader(Reader in, int sz) {
    super(in, sz);
    }

    /**
     * Set the current line number.
     */
    public void setLineNumber(int lineNumber) {
    this.lineNumber = lineNumber;
    }

    /**
     * Get the current line number.
     */
    public int getLineNumber() {
    return lineNumber;
    }

    /**
     * Read a single character.  Line terminators are compressed into single
     * newline ('\n') characters.
     *
     * @return     The character read, 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) {
        int c = super.read();
        if (skipLF) {
        if (c == '\n')
            c = super.read();
        skipLF = false;
        }
        switch (c) {
        case '\r':
        skipLF = true;
        case '\n':        /* Fall through */
        lineNumber++;
        return '\n';
        }
        return c;
    }
    }

    /**
     * Read characters into a portion of an array.
     *
     * @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 bytes read, or -1 if the end of the stream has
     *             already been reached
     *
     * @exception  IOException  If an I/O error occurs
     */
    public int read(char cbuf[], int off, int len) throws IOException {
    synchronized (lock) {
        int n = super.read(cbuf, off, len);

        for (int i = off; i < off + n; i++) {
        int c = cbuf[i];
        if (skipLF) {
            skipLF = false;
            if (c == '\n')
            continue;
        }
        switch (c) {
        case '\r':
            skipLF = true;
        case '\n':    /* Fall through */
            lineNumber++;
            break;
        }
        }

        return n;
    }
    }

    /**
     * Read a line of text.  A line is considered to be terminated by any one
     * of a line feed ('\n'), a carriage return ('\r'), or a carriage return
     * followed immediately by a linefeed.
     *
     * @return     A String containing the contents of the line, not including
     *             any line-termination characters, or null if the end of the
     *             stream has been reached
     *
     * @exception  IOException  If an I/O error occurs
     */
    public String readLine() throws IOException {
    synchronized (lock) {
        String l = super.readLine(skipLF);
            skipLF = false;
        if (l != null)
        lineNumber++;
        return l;
    }
    }

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

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

    /**
     * Skip characters.
     *
     * @param  n  The number of characters to skip
     *
     * @return    The number of characters actually skipped
     *
     * @exception  IOException  If an I/O error occurs
     */
    public long skip(long n) throws IOException {
    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;
    }
    }

    /**
     * Mark the present position in the stream.  Subsequent calls to reset()
     * will attempt to reposition the stream to this point, and will also reset
     * the line number appropriately.
     *
     * @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 an I/O error occurs
     */
    public void mark(int readAheadLimit) throws IOException {
    synchronized (lock) {
        super.mark(readAheadLimit);
        markedLineNumber = lineNumber;
            markedSkipLF     = skipLF;
    }
    }

    /**
     * Reset the stream to the most recent mark.
     *
     * @exception  IOException  If the stream has not been marked,
     *                          or if the mark has been invalidated
     */
    public void reset() throws IOException {
    synchronized (lock) {
        super.reset();
        lineNumber = markedLineNumber;
            skipLF     = markedSkipLF;
    }
    }

}