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1   /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 4.0 */
2   package net.sourceforge.pmd.ast;
3   
4   /***
5    * This interface describes a character stream that maintains line and
6    * column number positions of the characters.  It also has the capability
7    * to backup the stream to some extent.  An implementation of this
8    * interface is used in the TokenManager implementation generated by
9    * JavaCCParser.
10   * <p/>
11   * All the methods except backup can be implemented in any fashion. backup
12   * needs to be implemented correctly for the correct operation of the lexer.
13   * Rest of the methods are all used to get information like line number,
14   * column number and the String that constitutes a token and are not used
15   * by the lexer. Hence their implementation won't affect the generated lexer's
16   * operation.
17   */
18  
19  public interface CharStream {
20  
21      /***
22       * Returns the next character from the selected input.  The method
23       * of selecting the input is the responsibility of the class
24       * implementing this interface.  Can throw any java.io.IOException.
25       */
26      char readChar() throws java.io.IOException;
27  
28      /***
29       * Returns the column position of the character last read.
30       *
31       * @see #getEndColumn
32       * @deprecated
33       */
34      int getColumn();
35  
36      /***
37       * Returns the line number of the character last read.
38       *
39       * @see #getEndLine
40       * @deprecated
41       */
42      int getLine();
43  
44      /***
45       * Returns the column number of the last character for current token (being
46       * matched after the last call to BeginTOken).
47       */
48      int getEndColumn();
49  
50      /***
51       * Returns the line number of the last character for current token (being
52       * matched after the last call to BeginTOken).
53       */
54      int getEndLine();
55  
56      /***
57       * Returns the column number of the first character for current token (being
58       * matched after the last call to BeginTOken).
59       */
60      int getBeginColumn();
61  
62      /***
63       * Returns the line number of the first character for current token (being
64       * matched after the last call to BeginTOken).
65       */
66      int getBeginLine();
67  
68      /***
69       * Backs up the input stream by amount steps. Lexer calls this method if it
70       * had already read some characters, but could not use them to match a
71       * (longer) token. So, they will be used again as the prefix of the next
72       * token and it is the implemetation's responsibility to do this right.
73       */
74      void backup(int amount);
75  
76      /***
77       * Returns the next character that marks the beginning of the next token.
78       * All characters must remain in the buffer between two successive calls
79       * to this method to implement backup correctly.
80       */
81      char BeginToken() throws java.io.IOException;
82  
83      /***
84       * Returns a string made up of characters from the marked token beginning
85       * to the current buffer position. Implementations have the choice of returning
86       * anything that they want to. For example, for efficiency, one might decide
87       * to just return null, which is a valid implementation.
88       */
89      String GetImage();
90  
91      /***
92       * Returns an array of characters that make up the suffix of length 'len' for
93       * the currently matched token. This is used to build up the matched string
94       * for use in actions in the case of MORE. A simple and inefficient
95       * implementation of this is as follows :
96       * <p/>
97       * {
98       * String t = GetImage();
99       * return t.substring(t.length() - len, t.length()).toCharArray();
100      * }
101      */
102     char[] GetSuffix(int len);
103 
104     /***
105      * The lexer calls this function to indicate that it is done with the stream
106      * and hence implementations can free any resources held by this class.
107      * Again, the body of this function can be just empty and it will not
108      * affect the lexer's operation.
109      */
110     void Done();
111 
112 }