att.grappa
Class Lexer

java.lang.Object
  att.grappa.Lexer

public class Lexer
extends java.lang.Object

A class for doing lexical analysis of dot formatted input.

Version:

1.2, 21 Aug 2005; Copyright 1996 - 2005 by AT&T Corp.

Author:

John Mocenigo, Research @ AT&T Labs

Field Summary

private java.util.Hashtable	char_symbols
private java.lang.StringBuffer	cmnstrbuf common StringBuffer (suggested by Ginny Travers (bbn.com))
private int	current_line Current line number for use in error messages.
private int	current_position Character position in current line.
private static int	EOF_CHAR EOF constant.
private int	error_count Count of total errors detected so far.
private java.io.PrintWriter	errWriter
private boolean	haveId needed to handle anonymous subgraphs since parser has no precedence
private java.io.Reader	inReader
private java.util.Hashtable	keywords hash tables to hold symbols
private int	next_char First character of lookahead.
private int	next_char2 Second character of lookahead.
private int	old_char needed for retreating
private int	old_position
(package private) boolean	retreated
private int	warning_count Count of warnings issued so far

Constructor Summary

Lexer(java.io.Reader input, java.io.PrintWriter error)
Create an instance of Lexer that reads from input and sends error messages to error.

Method Summary

void	advance() Advance the scanner one character in the input stream.
private Symbol	do_html_string() Swallow up an html-like string.
private Symbol	do_id() Process an identifier.
private Symbol	do_quote_string() Swallow up a quote string.
private void	emit_error(java.lang.String message) Emit an error message.
private void	emit_warn(java.lang.String message) Emit a warning message.
private int	find_single_char(int ch) Try to look up a single character symbol, returns -1 for not found.
java.lang.String	getLocation() Get the current location in the form "[line_number(character_offser)]".
static boolean	id_char(char ch) Check if character is a valid id character;
static boolean	id_char(int ch) Check if character is a valid id character;
void	init() Initialize internal tables and read two characters of input for look-ahead purposes.
Symbol	next_token(int debugLevel) Return one Symbol.
private Symbol	real_next_token() The actual routine to return one Symbol.
private void	retreat()
private void	swallow_comment() Handle swallowing up a comment.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

next_char

private int next_char

First character of lookahead. Set to '\n' initially (needed for initial 2 calls to advance())

next_char2

private int next_char2

Second character of lookahead. Set to '\n' initially (needed for initial 2 calls to advance())

current_line

private int current_line

Current line number for use in error messages. Set to -1 to account for next_char/next_char2 initialization

current_position

private int current_position

Character position in current line.

EOF_CHAR

private static final int EOF_CHAR

EOF constant.

See Also:

Constant Field Values

haveId

private boolean haveId

needed to handle anonymous subgraphs since parser has no precedence

old_char

private int old_char

needed for retreating

old_position

private int old_position

retreated

boolean retreated

error_count

private int error_count

Count of total errors detected so far.

warning_count

private int warning_count

Count of warnings issued so far

keywords

private java.util.Hashtable keywords

hash tables to hold symbols

char_symbols

private java.util.Hashtable char_symbols

inReader

private java.io.Reader inReader

errWriter

private java.io.PrintWriter errWriter

cmnstrbuf

private java.lang.StringBuffer cmnstrbuf

common StringBuffer (suggested by Ginny Travers (bbn.com))

Constructor Detail

Lexer

public Lexer(java.io.Reader input,
             java.io.PrintWriter error)
      throws java.lang.IllegalArgumentException

Create an instance of Lexer that reads from input and sends error messages to error.

Parameters:

input - input Reader object

error - error output Writer object

Throws:

java.lang.IllegalArgumentException - whenever input is null

Method Detail

init

public void init()
          throws java.io.IOException

Initialize internal tables and read two characters of input for look-ahead purposes.

Throws:

java.io.IOException - if advance() does

See Also:

advance()

advance

public void advance()
             throws java.io.IOException

Advance the scanner one character in the input stream. This moves next_char2 to next_char and then reads a new next_char2.

Throws:

java.io.IOException - whenever a problem reading from input is encountered

retreat

private void retreat()

emit_error

private void emit_error(java.lang.String message)

Emit an error message. The message will be marked with both the current line number and the position in the line. Error messages are printed on print stream passed to Lexer (if any) and a GraphParserException is thrown.

Parameters:

message - the message to print.

getLocation

public java.lang.String getLocation()

Get the current location in the form "[line_number(character_offser)]".

Returns:

info about the current position in the input

emit_warn

private void emit_warn(java.lang.String message)

Emit a warning message. The message will be marked with both the current line number and the position in the line. Messages are printed on print stream passed to Lexer (if any).

Parameters:

message - the message to print.

id_char

public static boolean id_char(int ch)

Check if character is a valid id character;

Parameters:

ch - the character in question.

id_char

public static boolean id_char(char ch)

Check if character is a valid id character;

Parameters:

ch - the character in question.

find_single_char

private int find_single_char(int ch)

Try to look up a single character symbol, returns -1 for not found.

Parameters:

ch - the character in question.

swallow_comment

private void swallow_comment()
                      throws java.io.IOException

Handle swallowing up a comment. Both old style C and new style C++ comments are handled.

Throws:

java.io.IOException

do_quote_string

private Symbol do_quote_string()
                        throws java.io.IOException

Swallow up a quote string. Quote strings begin with a double quote and include all characters up to the first occurrence of another double quote (there is no way to include a double quote inside a quote string). The routine returns a Symbol object suitable for return by the scanner.

Throws:

java.io.IOException

do_html_string

private Symbol do_html_string()
                       throws java.io.IOException

Swallow up an html-like string. Html-like strings begin with a '<' and include all characters up to the first matching occurrence of a '>' The routine returns a Symbol object suitable for return by the scanner.

Throws:

java.io.IOException

do_id

private Symbol do_id()
              throws java.io.IOException

Process an identifier. Identifiers begin with a letter, underscore, or dollar sign, which is followed by zero or more letters, numbers, underscores or dollar signs. This routine returns an Symbol suitable for return by the scanner.

Throws:

java.io.IOException

real_next_token

private Symbol real_next_token()
                        throws java.io.IOException

The actual routine to return one Symbol. This is normally called from next_token(), but for debugging purposes can be called indirectly from debug_next_token().

Throws:

java.io.IOException

next_token

public Symbol next_token(int debugLevel)
                  throws java.io.IOException

Return one Symbol. This method is the main external interface to the scanner. It consumes sufficient characters to determine the next input Symbol and returns it.

Throws:

java.io.IOException - if advance() does