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LineNumberReader.java
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283 lines (260 loc) · 7.62 KB
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/*
* Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.io;
/**
* A buffered character-input stream that keeps track of line numbers. This
* class defines methods {@link #setLineNumber(int)} and {@link
* #getLineNumber()} for setting and getting the current line number
* respectively.
*
* <p> By default, line numbering begins at 0. This number increments at every
* <a href="#lt">line terminator</a> as the data is read, and can be changed
* with a call to <tt>setLineNumber(int)</tt>. Note however, that
* <tt>setLineNumber(int)</tt> does not actually change the current position in
* the stream; it only changes the value that will be returned by
* <tt>getLineNumber()</tt>.
*
* <p> A line is considered to be <a name="lt">terminated</a> by any one of a
* line feed ('\n'), a carriage return ('\r'), or a carriage return followed
* immediately by a linefeed.
*
* @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; // Defaults to 0
/** 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.
*
* @param in
* A Reader object to provide the underlying stream
*/
public LineNumberReader(Reader in) {
super(in);
}
/**
* Create a new line-numbering reader, reading characters into a buffer of
* the given size.
*
* @param in
* A Reader object to provide the underlying stream
*
* @param sz
* An int specifying the size of the buffer
*/
public LineNumberReader(Reader in, int sz) {
super(in, sz);
}
/**
* Set the current line number.
*
* @param lineNumber
* An int specifying the line number
*
* @see #getLineNumber
*/
public void setLineNumber(int lineNumber) {
this.lineNumber = lineNumber;
}
/**
* Get the current line number.
*
* @return The current line number
*
* @see #setLineNumber
*/
public int getLineNumber() {
return lineNumber;
}
/**
* Read a single character. <a href="#lt">Line terminators</a> are
* compressed into single newline ('\n') characters. Whenever a line
* terminator is read the current line number is incremented.
*
* @return The character read, or -1 if the end of the stream has been
* reached
*
* @throws IOException
* If an I/O error occurs
*/
@SuppressWarnings("fallthrough")
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. Whenever a <a
* href="#lt">line terminator</a> is read the current line number is
* incremented.
*
* @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
*
* @throws IOException
* If an I/O error occurs
*/
@SuppressWarnings("fallthrough")
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. Whenever a <a href="#lt">line terminator</a> is
* read the current line number is incremented.
*
* @return A String containing the contents of the line, not including
* any <a href="#lt">line termination characters</a>, or
* <tt>null</tt> if the end of the stream has been reached
*
* @throws 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
*
* @throws IOException
* If an I/O error occurs
*
* @throws IllegalArgumentException
* If <tt>n</tt> is negative
*/
public long skip(long n) throws IOException {
if (n < 0)
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;
}
}
/**
* 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.
*
* @throws 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.
*
* @throws 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;
}
}
}