001    /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 4.1 */
002    /* JavaCCOptions:STATIC=false */
003    package org.w3c.flute.parser;
004    
005    /**
006     * This interface describes a character stream that maintains line and
007     * column number positions of the characters.  It also has the capability
008     * to backup the stream to some extent.  An implementation of this
009     * interface is used in the TokenManager implementation generated by
010     * JavaCCParser.
011     *
012     * All the methods except backup can be implemented in any fashion. backup
013     * needs to be implemented correctly for the correct operation of the lexer.
014     * Rest of the methods are all used to get information like line number,
015     * column number and the String that constitutes a token and are not used
016     * by the lexer. Hence their implementation won't affect the generated lexer's
017     * operation.
018     */
019    
020    public interface CharStream {
021    
022      /**
023       * Returns the next character from the selected input.  The method
024       * of selecting the input is the responsibility of the class
025       * implementing this interface.  Can throw any java.io.IOException.
026       */
027      char readChar() throws java.io.IOException;
028    
029      /**
030       * Returns the column position of the character last read.
031       * @deprecated 
032       * @see #getEndColumn
033       */
034      int getColumn();
035    
036      /**
037       * Returns the line number of the character last read.
038       * @deprecated 
039       * @see #getEndLine
040       */
041      int getLine();
042    
043      /**
044       * Returns the column number of the last character for current token (being
045       * matched after the last call to BeginTOken).
046       */
047      int getEndColumn();
048    
049      /**
050       * Returns the line number of the last character for current token (being
051       * matched after the last call to BeginTOken).
052       */
053      int getEndLine();
054    
055      /**
056       * Returns the column number of the first character for current token (being
057       * matched after the last call to BeginTOken).
058       */
059      int getBeginColumn();
060    
061      /**
062       * Returns the line number of the first character for current token (being
063       * matched after the last call to BeginTOken).
064       */
065      int getBeginLine();
066    
067      /**
068       * Backs up the input stream by amount steps. Lexer calls this method if it
069       * had already read some characters, but could not use them to match a
070       * (longer) token. So, they will be used again as the prefix of the next
071       * token and it is the implemetation's responsibility to do this right.
072       */
073      void backup(int amount);
074    
075      /**
076       * Returns the next character that marks the beginning of the next token.
077       * All characters must remain in the buffer between two successive calls
078       * to this method to implement backup correctly.
079       */
080      char BeginToken() throws java.io.IOException;
081    
082      /**
083       * Returns a string made up of characters from the marked token beginning 
084       * to the current buffer position. Implementations have the choice of returning
085       * anything that they want to. For example, for efficiency, one might decide
086       * to just return null, which is a valid implementation.
087       */
088      String GetImage();
089    
090      /**
091       * Returns an array of characters that make up the suffix of length 'len' for
092       * the currently matched token. This is used to build up the matched string
093       * for use in actions in the case of MORE. A simple and inefficient
094       * implementation of this is as follows :
095       *
096       *   {
097       *      String t = GetImage();
098       *      return t.substring(t.length() - len, t.length()).toCharArray();
099       *   }
100       */
101      char[] GetSuffix(int len);
102    
103      /**
104       * The lexer calls this function to indicate that it is done with the stream
105       * and hence implementations can free any resources held by this class.
106       * Again, the body of this function can be just empty and it will not
107       * affect the lexer's operation.
108       */
109      void Done();
110    
111    }
112    /* JavaCC - OriginalChecksum=f97a7cd81439c70fe8694e5e66723c58 (do not edit this line) */