TokenLexer (eBus Utilities 5.0.0 API)

java.lang.Object
- net.sf.eBus.text.TokenLexer

```
public final class TokenLexer
extends Object
```
Provides a generalized token lexer capability. This lexer ability is beyond java.util.StringTokenizer in that it identifies the token type along with the token and converts the token string into the type's corresponding Java instance. There are nine (9) pre-defined token types and two special types: ERROR and EOF. ERROR is returned when an recoverable error occurred. EOF is returned when the input end is reached and no more tokens will be returned.
The pre-defined token types are:
1. CHARACTER: a single character between single quotes (').
2. COMMENT: Either a // or slash star comment. Supports nested comments.
3. FLOAT: A decimal number.
4. INTEGER: An integer number.
5. NAME: An alpha-numeric identifier.
6. OPERATOR: Punctuation only identifier.
7. SOURCE: Raw, unanalyzed input.
8. STRING: Zero or more characters between double quotes ("").
There is support for user-defined keyword, operator and delimiter tokens. When a NAME token is found, the user keywords map is checked if it contains the token as a keyword. If so, then the associated token type is returned instead of NAME. When a OPERATOR token is found, both the user operators and delimiters maps are checked.
The user-defined token maps should meet the following criteria:
- The token type values must be >= to NEXT_TOKEN.
- The token type values do not need be unique either within or across maps.
- The token type values do not need to be consecutive.
The basic algorithm using TokenLexer is:
```
   
 import java.io.Reader;
 import net.sf.eBus.text.TokenLexer;
 import net.sf.eBus.text.Token;
 ...
 TokenLexer lexer = new TokenLexer(Keywords, Operators, Delimiters);
 Token token;
 Reader input = ...;

 // Set the input to be tokenized.
 lexer.input(input);

 // Continue retrieving until no more tokens.
 while ((token = lexer.nextToken()).type() != TokenLexer.EOF)
 {
     // Process the next token based on token type.
 }

 // Finish up the tokenization.
   
 
```
Raw Lexical Mode

Users may not want the lexer to analyze input between two well-defined delimiters. This data is collected and returned as a SOURCE token when the terminating delimiter is reached. Raw mode requires both an an opening and closing delimiter specified. This allows the lexer to track the appearance of nested delimiters within the input and return only when the top-level terminating delimiter is found.

Raw lexical mode is used when input contains sub-text to be handled by a different lexer.
p
Author:

Charles Rapp

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`static class`	`TokenLexer.LexMode` The lexer will either analyze the tokens identifying the type or collect raw input until a terminating delimiter is found.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`CHARACTER` A single-quoted character token (2).
`static int`	`COMMENT` Either a `//` or a slash star comment (3).
`static int`	`EOF` The end of the input is reached (1).
`static int`	`ERROR` An error occurred when seeking the next token (0).
`static int`	`FLOAT` A floating point number (4).
`static int`	`INTEGER` An integer number (5).
`static int`	`NAME` An alphanumberic identifier (6).
`static int`	`NEXT_TOKEN` User-defined tokens must be >= 11.
`static char`	`NO_OPEN_CHAR` When the raw mode open character is set to U+0000, this means there is no open character, only a close character.
`static int`	`OPERATOR` Token consists solely of punctuation characters (7).
`static int`	`SOURCE` Raw, unanalyzed input (8).
`static int`	`STRING` A double-quoted string (9).
`static int`	`TOKEN_COUNT` There are eleven (11) predefined token types.

Constructor Summary

Constructors
Constructor and Description
`TokenLexer(Map<String,Integer> keywords, Map<String,Integer> operators, Map<Character,Integer> delimiters)` Creates a message layout lexer using the specified keywords, operator and delimiters.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`cookedMode()` Switch back to cooked tokenization.
`void`	`input(Reader reader)` Extract tokens from this input stream.
`int`	`lineNumber()` Returns the current line number being tokenized.
`TokenLexer.LexMode`	`mode()` Returns the current lexer mode.
`Token`	`nextToken()` Returns the next token found in the input stream.
`int`	`offset()` Returns the current offset into the input.
`void`	`rawMode(char openChar, char closeChar)` Switch to raw tokenization.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - NO_OPEN_CHAR
```
public static final char NO_OPEN_CHAR
```
    When the raw mode open character is set to U+0000, this means there is no open character, only a close character.
    
    See Also:
    
    Constant Field Values
  - ERROR
```
public static final int ERROR
```
    An error occurred when seeking the next token (0).
    
    See Also:
    
    Constant Field Values
  - EOF
```
public static final int EOF
```
    The end of the input is reached (1).
    
    See Also:
    
    Constant Field Values
  - CHARACTER
```
public static final int CHARACTER
```
    A single-quoted character token (2). Token value is a java.lang.Character instance.
    
    See Also:
    
    Constant Field Values
  - COMMENT
```
public static final int COMMENT
```
    Either a // or a slash star comment (3). Nested comments are supported.
    
    See Also:
    
    Constant Field Values
  - FLOAT
```
public static final int FLOAT
```
    A floating point number (4). Token value is a java.lang.Double instance.
    
    See Also:
    
    Constant Field Values
  - INTEGER
```
public static final int INTEGER
```
    An integer number (5). Token value is a java.lang.Long instance.
    
    See Also:
    
    Constant Field Values
  - NAME
```
public static final int NAME
```
    An alphanumberic identifier (6). If the token appears in the user-defined keywords map, then the user's token type is returned instead.
    
    See Also:
    
    Constant Field Values
  - OPERATOR
```
public static final int OPERATOR
```
    Token consists solely of punctuation characters (7). If the token is in the user-defined operator or delimiter map, then the user's token type is returned instead.
    Punctuation characters are:
```
   
 !  "  #  $  %  &  '  ( )  *
 +  ,  -  .  /  :  ;  <  =  >
 ?  @  [  \  ]  ^  _  `  {  }
 |  ~
   
 
```
    See Also:
    
    Constant Field Values
  - SOURCE
```
public static final int SOURCE
```
    Raw, unanalyzed input (8).
    
    See Also:
    
    TokenLexer.LexMode.RAW, Constant Field Values
  - STRING
```
public static final int STRING
```
    A double-quoted string (9).
    
    See Also:
    
    Constant Field Values
  - TOKEN_COUNT
```
public static final int TOKEN_COUNT
```
    There are eleven (11) predefined token types.
    
    See Also:
    
    Constant Field Values
  - NEXT_TOKEN
```
public static final int NEXT_TOKEN
```
    User-defined tokens must be >= 11.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - TokenLexer
```
public TokenLexer(Map<String,Integer> keywords,
                  Map<String,Integer> operators,
                  Map<Character,Integer> delimiters)
           throws IllegalArgumentException
```
    Creates a message layout lexer using the specified keywords, operator and delimiters. These maps may be empty but not null.
    
    Parameters:
    
    keywords - Keyword to integer identifier mapping.
    
    operators - Operator to integer identifier mapping.
    
    delimiters - Delimiter to integer identifier mapping.
    
    Throws:
    
    IllegalArgumentException - if any of the user maps contains a value < NEXT_TOKEN.
- Method Detail
  - lineNumber
```
public int lineNumber()
```
    Returns the current line number being tokenized.
    
    Returns:
    
    the current line number being tokenized.
  - offset
```
public int offset()
```
    Returns the current offset into the input.
    
    Returns:
    
    the current offset into the input.
  - mode
```
public TokenLexer.LexMode mode()
```
    Returns the current lexer mode.
    
    Returns:
    
    the current lexer mode.
  - input
```
public void input(Reader reader)
```
    Extract tokens from this input stream.
    
    Parameters:
    
    reader - Tokenize this input.
  - rawMode
```
public void rawMode(char openChar,
                    char closeChar)
```
    Switch to raw tokenization.
    
    Parameters:
    
    openChar - The open clause delimiter.
    
    closeChar - The close clause delimiter.
    
    See Also:
    
    cookedMode()
  - cookedMode
```
public void cookedMode()
```
    Switch back to cooked tokenization.
    
    See Also:
    
    rawMode(char, char)
  - nextToken
```
public Token nextToken()
```
    Returns the next token found in the input stream. If there are no more tokens in the input stream, then EOF is returned.
    
    Returns:
    
    the next token found in the input stream.

Class TokenLexer

Raw Lexical Mode

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

NO_OPEN_CHAR

ERROR

EOF

CHARACTER

COMMENT

FLOAT

INTEGER

NAME

OPERATOR

SOURCE

STRING

TOKEN_COUNT

NEXT_TOKEN

Constructor Detail

TokenLexer

Method Detail

lineNumber

offset

mode

input

rawMode

cookedMode

nextToken