Reader except that it
* counts line numbers, and canonicalizes newline characters. As data
* is read, whenever the char sequences "\r", "\n", or "\r\n" are encountered,
* the running line count is incremeted by one. Additionally, the whatever
* line termination sequence was encountered will be converted to a "\n"
* char. Note that this class numbers lines from 0. When the first
* line terminator is encountered, the line number is incremented to 1, and
* so on. Also note that actual "\r" and "\n" characters are looked for.
* The system dependent line separator sequence is ignored.
*
* This class counts only line termination characters. If the last line
* read from the stream does not end in a line termination sequence, it
* will not be counted as a line.
*
* @author Per Bothner (bothner@cygnus.com)
* @author Aaron M. Renn (arenn@urbanophile.com)
* @author Guilhem Lavaux (guilhem@kaffe.org)
* @date December 28, 2003.
*/
/* Written using "Java Class Libraries", 2nd edition, plus online
* API docs for JDK 1.2 beta from http://www.javasoft.com.
* Status: Believed complete and correct.
*
* This implementation has the feature that if '\r' is read, it
* does not look for a '\n', but immediately returns '\n'.
* On the next read(), if a '\n' is read, it is skipped.
* This has the advantage that we do not read (and hang) unnecessarily.
*
* This implementation is also minimal in the number of fields it uses.
*/
public class LineNumberReader extends BufferedReader
{
/** The current line number. */
private int lineNumber;
/** Whether we already found a new line in the former call. */
private boolean matchedNewLine;
/** The saved line number when calling mark() */
private int savedLineNumber;
/**
* Create a new LineNumberReader that reads from the
* specified subordinate Reader. A default 8K char sized
* buffer will be used for reads.
*
* @param in The subordinate Reader to read from
*/
public LineNumberReader(Reader in)
{
super(in, DEFAULT_BUFFER_SIZE);
}
/**
* This method initializes a new LineNumberReader to read
* from the specified subordinate Reader using the specified
* read buffer size.
*
* @param in The subordinate Reader to read from
* @param size The buffer size to use for reading
*/
public LineNumberReader(Reader in, int size)
{
super(in, size);
}
/**
* This method returns the current line number
*
* @return The current line number
*/
public int getLineNumber()
{
return lineNumber;
}
/**
* This method sets the current line number to the specified value.
*
* @param line_number The new line number
*/
public void setLineNumber(int lineNumber)
{
this.lineNumber = lineNumber;
}
/**
* This method marks a position in the input to which the stream can be
* "reset" char calling the reset() method. The parameter
* readlimit is the number of chars that can be read from the
* stream after setting the mark before the mark becomes invalid. For
* example, if mark() is called with a read limit of 10,
* then when
* 11 chars of data are read from the stream before the reset()
* method is called, then the mark is invalid and the stream object
* instance is not required to remember the mark.
*
* In this class, this method will remember the current line number as well
* as the current position in the stream. When the reset()
* method
* is called, the line number will be restored to the saved line number in
* addition to the stream position.
*
* @param readlimit The number of chars that can be read before the
* mark becomes invalid
*
* @exception IOException If an error occurs
*/
public void mark(int readLimit) throws IOException
{
if (readLimit < 0)
throw new IllegalArgumentException("Read-ahead limit is negative");
synchronized (lock)
{
// This is basically the same as BufferedReader.mark.
// However, if the previous character was a '\r', we need to
// save that 'r', in case the next character is a '\n'.
if (pos + readLimit > limit)
{
int saveCR = matchedNewLine ? 1 : 0;
char[] old_buffer = buffer;
if (readLimit > limit)
buffer = new char[saveCR + readLimit];
int copy_start = pos - saveCR;
savedLineNumber = lineNumber;
limit -= copy_start;
System.arraycopy(old_buffer, copy_start, buffer, 0, limit);
pos = saveCR;
}
markPos = pos;
}
}
/**
* This method resets a stream to the point where the mark()
* method
* was called. Any chars that were read after the mark point was set will
* be re-read during subsequent reads.
*
* In this class, this method will also restore the line number that was
* current when the mark() method was called.
*
* @exception IOException If an error occurs
*/
public void reset() throws IOException
{
synchronized (lock)
{
if (markPos < 0)
throw new IOException("mark never set or invalidated");
lineNumber = savedLineNumber;
pos = markPos;
matchedNewLine = (markPos > 0 && buffer[markPos-1] == '\r');
}
}
/**
* This private method fills the input buffer whatever pos is.
* Consequently pos should be checked before calling this method.
*
* @return the number of bytes actually read from the input stream or
* -1 if end of stream.
* @exception IOException If an error occurs.
*/
private int fill() throws IOException
{
if (markPos >= 0 && limit == buffer.length)
markPos = -1;
if (markPos < 0)
pos = limit = 0;
int count = in.read(buffer, limit, buffer.length - limit);
if (count <= 0)
return -1;
limit += count;
return count;
}
/**
* This method reads an unsigned char from the input stream and returns it
* as an int in the range of 0-65535. This method will return -1 if the
* end of the stream has been reached.
*
* Note that if a line termination sequence is encountered (ie, "\r", * "\n", or "\r\n") then that line termination sequence is converted to * a single "\n" value which is returned from this method. This means * that it is possible this method reads two chars from the subordinate * stream instead of just one. *
* Note that this method will block until a char of data is available
* to be read.
*
* @return The char read or -1 if end of stream
*
* @exception IOException If an error occurs
*/
public int read() throws IOException
{
synchronized (lock)
{
skipRedundantLF();
if (pos >= limit && fill() < 0)
return -1;
char ch = buffer[pos++];
if ((matchedNewLine = (ch == '\r')) || ch == '\n')
{
lineNumber++;
return '\n';
}
matchedNewLine = false;
return (int) ch;
}
}
/**
* This method reads chars from a stream and stores them into a caller
* supplied buffer. It starts storing data at index offset into
* the buffer and attemps to read len chars. This method can
* return before reading the number of chars requested. The actual number
* of chars read is returned as an int. A -1 is returned to indicated the
* end of the stream.
*
* This method will block until some data can be read. *
* Note that if a line termination sequence is encountered (ie, "\r",
* "\n", or "\r\n") then that line termination sequence is converted to
* a single "\n" value which is stored in the buffer. Only a single
* char is counted towards the number of chars read in this case.
*
* @param buf The array into which the chars read should be stored
* @param offset The offset into the array to start storing chars
* @param len The requested number of chars to read
*
* @return The actual number of chars read, or -1 if end of stream
*
* @exception IOException If an error occurs.
* @exception NullPointerException If buf is null (in any case).
* @exception IndexOutOfBoundsException If buffer parameters (offset and
* count) lies outside of the buffer capacity.
*/
public int read(char[] buf, int offset, int count) throws IOException
{
if (buf == null)
throw new NullPointerException();
if (offset + count > buf.length || offset < 0)
throw new IndexOutOfBoundsException();
if (count <= 0)
{
if (count < 0)
throw new IndexOutOfBoundsException();
return 0;
}
synchronized (lock)
{
if (pos >= limit && fill() < 0)
return -1;
int start_offset = offset;
boolean matched = matchedNewLine;
while (count-- > 0 && pos < limit)
{
char ch = buffer[pos++];
if (ch == '\r')
{
lineNumber++;
matched = true;
}
else if (ch == '\n' && !matched)
lineNumber++;
else
matched = false;
buf[offset++] = ch;
}
matchedNewLine = matched;
return offset - start_offset;
}
}
private void skipRedundantLF() throws IOException
{
if (pos > 0 && matchedNewLine)
{
if (pos < limit)
{ // fast case
if (buffer[pos] == '\n')
pos++;
}
else
{ // check whether the next buffer begins with '\n'.
// in that case kill the '\n'.
if (fill() <= 0)
return;
if (buffer[pos] == '\n')
pos++;
}
matchedNewLine = true;
}
}
/**
* This method reads a line of text from the input stream and returns
* it as a String. A line is considered to be terminated
* by a "\r", "\n", or "\r\n" sequence, not by the system dependent line
* separator.
*
* @return The line read as a String or null
* if end of stream.
*
* @exception IOException If an error occurs
*/
public String readLine() throws IOException
{
// BufferedReader.readLine already does this. Shouldn't need to keep
// track of newlines (since the read method deals with this for us).
// But if the buffer is large, we may not call the read method at all
// and super.readLine can't increment lineNumber itself.
// Though it may seem kludgy, the safest thing to do is to save off
// lineNumber and increment it explicitly when we're done (iff we
// ended with a '\n' or '\r' as opposed to EOF).
//
// Also, we need to undo the special casing done by BufferedReader.readLine
// when a '\r' is the last char in the buffer. That situation is marked
// by 'pos > limit'.
int tmpLineNumber = lineNumber;
skipRedundantLF();
String str = super.readLine();
if (pos > limit)
--pos;
// The only case where you mustn't increment the line number is you are
// at the EOS.
if (str != null)
lineNumber = tmpLineNumber + 1;
return str;
}
/**
* This method skips over characters in the stream. This method will
* skip the specified number of characters if possible, but is not required
* to skip them all. The actual number of characters skipped is returned.
* This method returns 0 if the specified number of chars is less than 1.
*
* @param count The specified number of chars to skip.
*
* @return The actual number of chars skipped.
*
* @exception IOException If an error occurs
*/
public long skip (long count) throws IOException
{
if (count < 0)
throw new IllegalArgumentException("skip() value is negative");
if (count == 0)
return 0;
int skipped;
char[] buf = new char[1];
for (skipped = 0; skipped < count; skipped++)
{
int ch = read(buf, 0, 1);
if (ch < 0)
break;
}
return skipped;
}
}