src/java.base/share/classes/java/io/LineNumberInputStream.java

/*
 * Copyright (c) 1995, 2023, 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;

import java.util.Objects;

/**
 * This class is an input stream filter that provides the added
 * functionality of keeping track of the current line number.
 * <p>
 * A line is a sequence of bytes ending with a carriage return
 * character ({@code '\u005Cr'}), a newline character
 * ({@code '\u005Cn'}), or a carriage return character followed
 * immediately by a linefeed character. In all three cases, the line
 * terminating character(s) are returned as a single newline character.
 * <p>
 * The line number begins at {@code 0}, and is incremented by
 * {@code 1} when a {@code read} returns a newline character.
 *
 * @author     Arthur van Hoff
 * @see        java.io.LineNumberReader
 * @since      1.0
 * @deprecated This class incorrectly assumes that bytes adequately represent
 *             characters.  As of JDK&nbsp;1.1, the preferred way to operate on
 *             character streams is via the new character-stream classes, which
 *             include a class for counting line numbers.
 */
@Deprecated
public class LineNumberInputStream extends FilterInputStream {
    int pushBack = -1;
    int lineNumber;
    int markLineNumber;
    int markPushBack = -1;

    /**
     * Constructs a newline number input stream that reads its input
     * from the specified input stream.
     *
     * @param      in   the underlying input stream.
     */
    public LineNumberInputStream(InputStream in) {
        super(in);
    }

    /**
     * Reads the next byte of data from this input stream. The value
     * byte is returned as an {@code int} in the range
     * {@code 0} to {@code 255}. If no byte is available
     * because the end of the stream has been reached, the value
     * {@code -1} is returned. This method blocks until input data
     * is available, the end of the stream is detected, or an exception
     * is thrown.
     * <p>
     * The {@code read} method of
     * {@code LineNumberInputStream} calls the {@code read}
     * method of the underlying input stream. It checks for carriage
     * returns and newline characters in the input, and modifies the
     * current line number as appropriate. A carriage-return character or
     * a carriage return followed by a newline character are both
     * converted into a single newline character.
     *
     * @return     the next byte of data, or {@code -1} if the end of this
     *             stream is reached.
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     * @see        java.io.LineNumberInputStream#getLineNumber()
     */
    @SuppressWarnings("fallthrough")
    public int read() throws IOException {
        int c = pushBack;

        if (c != -1) {
            pushBack = -1;
        } else {
            c = in.read();
        }

        switch (c) {
          case '\r':
            pushBack = in.read();
            if (pushBack == '\n') {
                pushBack = -1;
            }
          case '\n':
            lineNumber++;
            return '\n';
        }
        return c;
    }

    /**
     * Reads up to {@code len} bytes of data from this input stream
     * into an array of bytes. This method blocks until some input is available.
     * <p>
     * The {@code read} method of
     * {@code LineNumberInputStream} repeatedly calls the
     * {@code read} method of zero arguments to fill in the byte array.
     *
     * @param      b     the buffer into which the data is read.
     * @param      off   the start offset of the data.
     * @param      len   the maximum number of bytes read.
     * @return     the total number of bytes read into the buffer, or
     *             {@code -1} if there is no more data because the end of
     *             this stream has been reached.
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.LineNumberInputStream#read()
     */
    public int read(byte[] b, int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        }
        Objects.checkFromIndexSize(off, len, b.length);
        if (len == 0) {
            return 0;
        }

        int c = read();
        if (c == -1) {
            return -1;
        }
        b[off] = (byte)c;

        int i = 1;
        try {
            for (; i < len ; i++) {
                c = read();
                if (c == -1) {
                    break;
                }
                b[off + i] = (byte)c;
            }
        } catch (IOException ee) {
        }
        return i;
    }

    /**
     * Skips over and discards {@code n} bytes of data from this
     * input stream. The {@code skip} method may, for a variety of
     * reasons, end up skipping over some smaller number of bytes,
     * possibly {@code 0}. The actual number of bytes skipped is
     * returned.  If {@code n} is negative, no bytes are skipped.
     * <p>
     * The {@code skip} method of {@code LineNumberInputStream} creates
     * a byte array and then repeatedly reads into it until
     * {@code n} bytes have been read or the end of the stream has
     * been reached.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public long skip(long n) throws IOException {
        int chunk = 2048;
        long remaining = n;
        byte data[];
        int nr;

        if (n <= 0) {
            return 0;
        }

        data = new byte[chunk];
        while (remaining > 0) {
            nr = read(data, 0, (int) Math.min(chunk, remaining));
            if (nr < 0) {
                break;
            }
            remaining -= nr;
        }

        return n - remaining;
    }

    /**
     * Sets the line number to the specified argument.
     *
     * @param      lineNumber   the new line number.
     * @see #getLineNumber
     */
    public void setLineNumber(int lineNumber) {
        this.lineNumber = lineNumber;
    }

    /**
     * Returns the current line number.
     *
     * @return     the current line number.
     * @see #setLineNumber
     */
    public int getLineNumber() {
        return lineNumber;
    }


    /**
     * Returns the number of bytes that can be read from this input
     * stream without blocking.
     * <p>
     * Note that if the underlying input stream is able to supply
     * <i>k</i> input characters without blocking, the
     * {@code LineNumberInputStream} can guarantee only to provide
     * <i>k</i>/2 characters without blocking, because the
     * <i>k</i> characters from the underlying input stream might
     * consist of <i>k</i>/2 pairs of {@code '\u005Cr'} and
     * {@code '\u005Cn'}, which are converted to just
     * <i>k</i>/2 {@code '\u005Cn'} characters.
     *
     * @return     the number of bytes that can be read from this input stream
     *             without blocking.
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    public int available() throws IOException {
        return (pushBack == -1) ? super.available()/2 : super.available()/2 + 1;
    }

    /**
     * Marks the current position in this input stream. A subsequent
     * call to the {@code reset} method repositions this stream at
     * the last marked position so that subsequent reads re-read the same bytes.
     * <p>
     * The {@code mark} method of
     * {@code LineNumberInputStream} remembers the current line
     * number in a private variable, and then calls the {@code mark}
     * method of the underlying input stream.
     *
     * @param   readlimit   the maximum limit of bytes that can be read before
     *                      the mark position becomes invalid.
     * @see     java.io.FilterInputStream#in
     * @see     java.io.LineNumberInputStream#reset()
     */
    public void mark(int readlimit) {
        markLineNumber = lineNumber;
        markPushBack   = pushBack;
        in.mark(readlimit);
    }

    /**
     * Repositions this stream to the position at the time the
     * {@code mark} method was last called on this input stream.
     * <p>
     * The {@code reset} method of
     * {@code LineNumberInputStream} resets the line number to be
     * the line number at the time the {@code mark} method was
     * called, and then calls the {@code reset} method of the
     * underlying input stream.
     * <p>
     * Stream marks are intended to be used in
     * situations where you need to read ahead a little to see what's in
     * the stream. Often this is most easily done by invoking some
     * general parser. If the stream is of the type handled by the
     * parser, it just chugs along happily. If the stream is not of
     * that type, the parser should toss an exception when it fails,
     * which, if it happens within readlimit bytes, allows the outer
     * code to reset the stream and try another parser.
     *
     * @throws     IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     * @see        java.io.LineNumberInputStream#mark(int)
     */
    public void reset() throws IOException {
        lineNumber = markLineNumber;
        pushBack   = markPushBack;
        in.reset();
    }
}