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Java > Open Source Codes > net > sourceforge > pmd > ast > CharStream


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 JavaDoc;
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 JavaDoc;
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 JavaDoc 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 }
113
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