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;
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;
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 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 }