001 /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 4.1 */ 002 /* JavaCCOptions:STATIC=false */ 003 package org.w3c.flute.parser; 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=f97a7cd81439c70fe8694e5e66723c58 (do not edit this line) */