Interpreter.Sexp.Utils.Lexer
Class StreamTokenizerWithAtom

java.lang.Object
  |
  +--Interpreter.Sexp.Utils.Lexer.StreamTokenizerWithAtom

Direct Known Subclasses:

Interpreter.Sexp.Utils.Lexer.LexerMask

public class StreamTokenizerWithAtom

extends java.lang.Object

The StreamTokenizerWithAtom class takes an input stream and parses it into "tokens", allowing the tokens to be read one at a time. The parsing process is controlled by a table and a number of flags that can be set to various states. The stream tokenizer can recognize identifiers, numbers, atoms, quoted strings, and various comment styles.

Each byte read from the input stream is regarded as a character in the range '\u0000' through '\u00FF'. The character value is used to look up six possible attributes of the character: white space, alphabetic, numeric, atom, string quote, and comment character. Each character can have zero or more of these attributes.

In addition, an instance has four flags. These flags indicate:

• Whether line terminators are to be returned as tokens or treated as white space that merely separates tokens.
• Whether C-style comments are to be recognized and skipped.
• Whether C++-style comments are to be recognized and skipped.
• Whether the characters of identifiers are converted to lowercase.

A typical application first constructs an instance of this class, sets up the syntax tables, and then repeatedly loops calling the nextToken method in each iteration of the loop until it returns the value TT_EOF.

Since:

JDK1.0

Author:

James Gosling

See Also:

nextToken(), TT_EOF

Field Summary

boolean	nospaces This field is false if the current token follows a white space, else this field is true.
double	nval If the current token is a number, this field contains the value of that number.
java.lang.String	sval If the current token is a word token or an atom token, this field contains a string giving the characters of the word token or the atom token.
static int	TT_ATOM A constant indicating that an atom token has been read.
static int	TT_EOF A constant indicating that the end of the stream has been read.
static int	TT_EOL A constant indicating that the end of the line has been read.
static int	TT_NUMBER A constant indicating that a number token has been read.
static int	TT_WORD A constant indicating that a word token has been read.
int	ttype After a call to the nextToken method, this field contains the type of the token just read.

Constructor Summary

StreamTokenizerWithAtom(java.io.InputStream is)
Deprecated. As of JDK version 1.1, the preferred way to tokenize an input stream is to convert it into a character stream, for example:

	Reader r = new BufferedReader(new InputStreamReader(is));
	StreamTokenizerWithAtom st = new StreamTokenizerWithAtom(r);
 

StreamTokenizerWithAtom(java.io.Reader r)
Create a tokenizer that parses the given character stream.

Method Summary

void	atom(java.lang.String atom) Specifies that the string atom is a token.
void	commentChar(int ch) Specified that the character argument starts a single-line comment.
void	eolIsSignificant(boolean flag) Determines whether or not ends of line are treated as tokens.
int	lineno() Return the current line number.
void	lowerCaseMode(boolean fl) Determines whether or not word token are automatically lowercased.
int	nextToken() Parses the next token from the input stream of this tokenizer.
void	ordinaryChar(int ch) Specifies that the character argument is "ordinary" in this tokenizer.
void	ordinaryChars(int low, int hi) Specifies that all characters c in the range low <= c <= high are "ordinary" in this tokenizer.
void	parseNumbers() Specifies that numbers should be parsed by this tokenizer.
void	pushBack() Causes the next call to the nextToken method of this tokenizer to return the current value in the ttype field, and not to modify the value in the nval or sval field.
void	quoteChar(int ch) Specifies that matching pairs of this character delimit string constants in this tokenizer.
void	resetSyntax() Resets this tokenizer's syntax table so that all characters are "ordinary."
void	slashSlashComments(boolean flag) Determines whether or not the tokenizer recognizes C++-style comments.
void	slashStarComments(boolean flag) Determines whether or not the tokenizer recognizes C-style comments.
java.lang.String	toString() Returns the string representation of the current stream token.
void	whitespaceChars(int low, int hi) Specifies that all characters c in the range low <= c <= high are white space characters.
void	wordChars(int low, int hi) Specifies that all characters c in the range low <= c <= high are word constituents.

Methods inherited from class java.lang.Object

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

Field Detail

ttype

public int ttype

After a call to the nextToken method, this field contains the type of the token just read. For a single character token, its value is the single character, converted to an integer. For a quoted string token (see quoteChare(int)), its value is the quote character. Otherwise, its value is one of the following:

• TT_WORD indicates that the token is a word.
• TT_ATOM indicates that the token is an atom.
• TT_NUMBER indicates that the token is a number.
• TT_EOL indicates that the end of line has been read. The field can only have this value if the eolIsSignificant method has been called with the argument true.
• TT_EOF indicates that the end of the input stream has been reached.

See Also:

eolIsSignificant(boolean), nextToken(), quoteChar(int), TT_EOF, TT_EOL, TT_NUMBER, TT_WORD

TT_EOF

public static final int TT_EOF

A constant indicating that the end of the stream has been read.

TT_EOL

public static final int TT_EOL

A constant indicating that the end of the line has been read.

TT_NUMBER

public static final int TT_NUMBER

A constant indicating that a number token has been read.

TT_WORD

public static final int TT_WORD

A constant indicating that a word token has been read.

TT_ATOM

public static final int TT_ATOM

A constant indicating that an atom token has been read.

sval

public java.lang.String sval

If the current token is a word token or an atom token, this field contains a string giving the characters of the word token or the atom token. When the current token is a quoted string token, this field contains the body of the string.

The current token is a word when the value of the ttype field is TT_WORD. The current token is a quoted string token when the value of the ttype field is a quote character.

See Also:

quoteChar(int), TT_WORD, ttype

nval

public double nval

If the current token is a number, this field contains the value of that number. The current token is a number when the value of the ttype field is TT_NUMBER.

See Also:

TT_NUMBER, ttype

nospaces

public boolean nospaces

This field is false if the current token follows a white space, else this field is true.

See Also:

whitespaceChars(int,int), atom(String)

Constructor Detail

StreamTokenizerWithAtom

public StreamTokenizerWithAtom(java.io.InputStream is)

Deprecated. As of JDK version 1.1, the preferred way to tokenize an input stream is to convert it into a character stream, for example:

	Reader r = new BufferedReader(new InputStreamReader(is));
	StreamTokenizerWithAtom st = new StreamTokenizerWithAtom(r);
 

Creates a stream tokenizer that parses the specified input stream. The stream tokenizer is initialized to the following default state:

• All byte values 'A' through 'Z', 'a' through 'z', and '\u00A0' through '\u00FF' are considered to be alphabetic.
• All byte values '\u0000' through '\u0020' are considered to be white space.
• '/' is a comment character.
• Single quote '\'' and double quote '"' are string quote characters.
• Numbers are parsed.
• Ends of lines are treated as white space, not as separate tokens.
• C-style and C++-style comments are not recognized.

Parameters:

is - an input stream.

See Also:

StreamTokenizerWithAtom(Reader)

StreamTokenizerWithAtom

public StreamTokenizerWithAtom(java.io.Reader r)

Create a tokenizer that parses the given character stream.

Since:

JDK1.1

Method Detail

resetSyntax

public void resetSyntax()

Resets this tokenizer's syntax table so that all characters are "ordinary." See the ordinaryChar method for more information on a character being ordinary.

See Also:

ordinaryChar(int)

wordChars

public void wordChars(int low,
                      int hi)

Specifies that all characters c in the range low <= c <= high are word constituents. A word token consists of a word constituent followed by zero or more word constituents or number constituents.

Parameters:

low - the low end of the range.

hi - the high end of the range.

atom

public void atom(java.lang.String atom)

Specifies that the string atom is a token. This is useful if you have an operator that consists of 2 or more characters such as "==", ">=", ":=", etc.
They cannot be considered part of a word, neither they can be considered as the sequence of 2 or more ordinaryChars since you could not know if they are separated by whiteSpaces (well, it is possible to know if they are separated by whiteSpaces using the field nospaces, but then it's necessary to put the single characters together to create a single token).
The first character of an atom should be an ordinaryChar, otherwise the atom would be found only if:

• It is at the beginning of a word if the first character is a costituent of a word (see wordChars(int,int)).
• It is at the beginning of a whiteSpace if the first character is a whiteSpaceChar.

If the firs character is not in the range ASCII 1-256 then nothing would be performed by the atom method.
More atoms can begin with the same character.

If ordinaryChar, quoteChar or commentChar is performed on the first character after the atom method, then the atom would not be recognized any more.

Parameters:

atom - the atom string.

See Also:

wordChars(int,int), ordinaryChar(int), nospaces

whitespaceChars

public void whitespaceChars(int low,
                            int hi)

Specifies that all characters c in the range low <= c <= high are white space characters. White space characters serve only to separate tokens in the input stream.

Parameters:

low - the low end of the range.

hi - the high end of the range.

ordinaryChars

public void ordinaryChars(int low,
                          int hi)

Specifies that all characters c in the range low <= c <= high are "ordinary" in this tokenizer. See the ordinaryChar method for more information on a character being ordinary.

Parameters:

low - the low end of the range.

hi - the high end of the range.

See Also:

ordinaryChar(int)

ordinaryChar

public void ordinaryChar(int ch)

Specifies that the character argument is "ordinary" in this tokenizer. It removes any special significance the character has as a comment character, word component, string delimiter, white space, or number character. When such a character is encountered by the parser, the parser treates it as a single-character token and sets ttype field to the character value.

Parameters:

ch - the character.

See Also:

ttype

commentChar

public void commentChar(int ch)

Specified that the character argument starts a single-line comment. All characters from the comment character to the end of the line are ignored by this stream tokenizer.

Parameters:

ch - the character.

quoteChar

public void quoteChar(int ch)

Specifies that matching pairs of this character delimit string constants in this tokenizer.

When the nextToken method encounters a string constant, the ttype field is set to the string delimiter and the sval field is set to the body of the string.

If a string quote character is encountered, then a string is recognized, consisting of all characters after (but not including) the string quote character, up to (but not including) the next occurrence of that same string quote character, or a line terminator, or end of file. The usual escape sequences such as "\n" and "\t" are recognized and converted to single characters as the string is parsed.

Parameters:

ch - the character.

See Also:

nextToken(), sval, ttype

parseNumbers

public void parseNumbers()

Specifies that numbers should be parsed by this tokenizer. The syntax table of this tokenizer is modified so that each of the twelve characters:

		0 1 2 3 4 5 6 7 8 9 . -
 

has the "numeric" attribute.

When the parser encounters a word token that has the format of a double precision floating-point number, it treats the token as a number rather than a word, by setting the the ttype field to the value TT_NUMBER and putting the numeric value of the token into the nval field.

See Also:

nval, TT_NUMBER, ttype

eolIsSignificant

public void eolIsSignificant(boolean flag)

Determines whether or not ends of line are treated as tokens. If the flag argument is true, this tokenizer treats end of lines as tokens; the nextToken method returns TT_EOL and also sets the ttype field to this value when an end of line is read.

A line is a sequence of characters ending with either a carriage-return character ('\r') or a newline character ('\n'). In addition, a carriage-return character followed immediately by a newline character is treated as a single end-of-line token.

If the flag is false, end-of-line characters are treated as white space and serve only to separate tokens.

Parameters:

flag - true indicates that end-of-line characters are separate tokens; false indicates that end-of-line characters are white space.

See Also:

nextToken(), ttype, TT_EOL

slashStarComments

public void slashStarComments(boolean flag)

Determines whether or not the tokenizer recognizes C-style comments. If the flag argument is true, this stream tokenizer recognizes C-style comments. All text between successive occurrences of /* and */ are discarded.

If the flag argument is false, then C-style comments are not treated specially.

slashSlashComments

public void slashSlashComments(boolean flag)

Determines whether or not the tokenizer recognizes C++-style comments. If the flag argument is true, this stream tokenizer recognizes C++-style comments. Any occurrence of two consecutive slash characters ('/') is treated as the beginning of a comment that extends to the end of the line.

If the flag argument is false, then C++-style comments are not treated specially.

Parameters:

flag - true indicates to recognize and ignore C++-style comments.

lowerCaseMode

public void lowerCaseMode(boolean fl)

Determines whether or not word token are automatically lowercased. If the flag argument is true, then the value in the sval field is lowercased whenever a word token is returned (the ttype field has the value TT_WORD by the nextToken method of this tokenizer.

If the flag argument is false, then the sval field is not modified.

Parameters:

fl - true indicates that all word tokens should be lowercased.

See Also:

nextToken(), ttype, TT_WORD

nextToken

public int nextToken()
              throws java.io.IOException

Parses the next token from the input stream of this tokenizer. The type of the next token is returned in the ttype field. Additional information about the token may be in the nval field or the sval field of this tokenizer.

Typical clients of this class first set up the syntax tables and then sit in a loop calling nextToken to parse successive tokens until TT_EOF is returned.

Returns:

the value of the ttype field.

See Also:

nval, sval, ttype

pushBack

public void pushBack()

Causes the next call to the nextToken method of this tokenizer to return the current value in the ttype field, and not to modify the value in the nval or sval field.

See Also:

nextToken(), nval, sval, ttype

lineno

public int lineno()

Return the current line number.

Returns:

the current line number of this stream tokenizer.

toString

public java.lang.String toString()

Returns the string representation of the current stream token.

Returns:

a string representation of the token specified by the ttype, nval, and sval fields.

Overrides:

toString in class java.lang.Object

See Also:

nval, sval, ttype