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Java > Open Source Codes > org > apache > velocity > runtime > parser > CharStream


1 /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 2.1 */
2 package org.apache.velocity.runtime.parser;
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  *
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    * @deprecated
31    * @see #getEndColumn
32    */
33   int getColumn();
34
35   /**
36    * Returns the line number of the character last read.
37    * @deprecated
38    * @see #getEndLine
39    */
40   int getLine();
41
42   /**
43    * Returns the column number of the last character for current token (being
44    * matched after the last call to BeginTOken).
45    */
46   int getEndColumn();
47
48   /**
49    * Returns the line number of the last character for current token (being
50    * matched after the last call to BeginTOken).
51    */
52   int getEndLine();
53
54   /**
55    * Returns the column number of the first character for current token (being
56    * matched after the last call to BeginTOken).
57    */
58   int getBeginColumn();
59
60   /**
61    * Returns the line number of the first character for current token (being
62    * matched after the last call to BeginTOken).
63    */
64   int getBeginLine();
65
66   /**
67    * Backs up the input stream by amount steps. Lexer calls this method if it
68    * had already read some characters, but could not use them to match a
69    * (longer) token. So, they will be used again as the prefix of the next
70    * token and it is the implemetation's responsibility to do this right.
71    */
72   void backup(int amount);
73
74   /**
75    * Returns the next character that marks the beginning of the next token.
76    * All characters must remain in the buffer between two successive calls
77    * to this method to implement backup correctly.
78    */
79   char BeginToken() throws java.io.IOException JavaDoc;
80
81   /**
82    * Returns a string made up of characters from the marked token beginning
83    * to the current buffer position. Implementations have the choice of returning
84    * anything that they want to. For example, for efficiency, one might decide
85    * to just return null, which is a valid implementation.
86    */
87   String JavaDoc GetImage();
88
89   /**
90    * Returns an array of characters that make up the suffix of length 'len' for
91    * the currently matched token. This is used to build up the matched string
92    * for use in actions in the case of MORE. A simple and inefficient
93    * implementation of this is as follows :
94    *
95    * {
96    * String t = GetImage();
97    * return t.substring(t.length() - len, t.length()).toCharArray();
98    * }
99    */
100   char[] GetSuffix(int len);
101
102   /**
103    * The lexer calls this function to indicate that it is done with the stream
104    * and hence implementations can free any resources held by this class.
105    * Again, the body of this function can be just empty and it will not
106    * affect the lexer's operation.
107    */
108   void Done();
109
110 }
111
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