* This class is used as an abtract base class upon which to implement any kind
* of lexical analyzer (lexer), which reads characters from an input source
* stream (implementing the java.io.Reader class) and converting it into
* a stream of tokens (which implement the {@link TokenI} interface).
* Such a lexer stream can be used to read the underlying source text for a
* parser, such as those implementing the {@link ParserI} interface.
*
* @version $Revision: 1.5 $ $Date: 2003/02/26 04:41:16 $
* @since 2001-07-17
* @author
* David R. Tribble,
* david@tribble.com.
*
* Copyright
* ©2001-2003 by David R. Tribble all rights reserved.
*
* Permission is granted to freely use and distribute this source code
* provided that the original copyright and authorship notices remain
* intact.
*
* @see ParserI
* @see TokenI
* @see CharReader
*/
public abstract class LexerAdapter
implements LexerI, DiagnosticWriterI
{
// Identification
/** Revision information. */
static final String REV =
"@(#)tribble/io/LexerAdapter.java $Revision: 1.5 $ $Date: 2003/02/26 04:41:16 $\n";
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Constants
// (None)
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Static methods
// (None)
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Protected variables
/** Lexer input stream. */
protected Reader m_in;
/** Diagnostic message output stream. */
protected DiagnosticOutputI m_out;
/** Input source filename. */
protected String m_fName;
/** Input source line number. */
protected int m_lineNo = 1;
/** Input source column number. */
protected int m_colNo = 1;
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Public constructors
/***************************************************************************
* Constructor.
*
* @param in
* A character input stream from which to read tokens.
*
* @since 1.5, 2002-02-25
*/
public LexerAdapter(Reader in)
{
// Establish the input stream for this lexer
setInput(in);
}
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// Public methods
/***************************************************************************
* Establish the output stream to which diagnostic messages (warning and
* error messages) are written during parsing.
*
* @param out
* The error output stream.
*
* @since 1.1, 2001-07-17
*/
public synchronized void setOutput(DiagnosticOutputI out)
//implements tribble.io.DiagnosticWriterI
{
// Establish the diagnostic output stream
m_out = out;
}
/***************************************************************************
* Establish the input stream for this lexer from which to read tokens.
*
* @param in
* A character input stream from which to read tokens.
*
* @since 1.5, 2002-02-25
*/
public synchronized void setInput(Reader in)
//implements tribble.io.LexerI
{
// Establish the input stream for this lexer
m_in = in;
}
/***************************************************************************
* Establish the input source filename.
*
* @param fname
* The source filename.
*
* @since 1.1, 2001-07-17
*/
public synchronized void setSourceName(String fname)
//implements tribble.io.LexerI
{
// Establish the input source filename
m_fName = fname;
}
/***************************************************************************
* Close and disassociate the underlying input stream from this lexer.
*
* @since 1.1, 2001-07-17
*/
public synchronized void close()
//implements tribble.io.LexerI
{
try
{
// Close the input stream
if (m_in != null)
{
synchronized (m_in)
{
m_in.close();
}
}
}
catch (IOException ex)
{
// Ignored
}
// Disassociate the underlying input stream from this lexer
m_in = null;
}
/***************************************************************************
* Read the next token from the input stream.
*
*
* Either this method or {@link #getToken(TokenI)} may be used * interchangeably. * * @return * The next token read from the input stream, or null if there are no more * tokens (i.e., the end of the token input stream was reached). * * @throws IOException * Thrown if an I/O error or parsing error occurs. * * @since 1.1, 2001-07-17 */ public TokenI getToken() throws IOException //implements tribble.io.LexerI { TokenAdapter tok; // Create and fill a new token tok = new TokenAdapter(); if (getToken(tok)) return (tok); else return (null); } /*************************************************************************** * Read the next token from the lexer input stream. * *
* Either this method or {@link #getToken()} may be used interchangeably. * This method might be more efficient, since a new token object does not * need to be allocated on each call. * * @param tok * The token object which is filled in with the next token read from the * input stream. * * @return * True if a token was successfully read from the input stream, otherwise * false (i.e., the end of the token input stream was reached). * * @throws IOException * Thrown if an I/O error or parsing error occurs. * * @since 1.1, 2001-07-17 */ public abstract boolean getToken(TokenI tok) throws IOException; //implements tribble.io.LexerI // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - // Protected constructors /*************************************************************************** * Default constructor. * * @since 1.1, 2001-07-17 */ protected LexerAdapter() { // Do nothing } // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - // Protected methods /*************************************************************************** * Finalization. * Close and disassociate the input stream ({@link #m_in}) from this lexer. * Also disassociates the diagnostic output stream ({@link #m_out}) from this * lexer. * * @since 1.1, 2001-07-17 */ protected synchronized void finalize() throws Throwable { // Close the input stream close(); // Note: Do not close the diagnostic output stream 'm_out' // Disassociate the diagnostic output stream from this lexer m_out = null; // Cascade super.finalize(); } } // End LexerAdapter.java