001 /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 4.1 */
002 /* JavaCCOptions:STATIC=true */
003 package net.sourceforge.pmd.lang.ast;
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=0c387fa4d138cb757cb48b36d8bfec55 (do not edit this line) */
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