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The source code/* * Sun Public License Notice * * The contents of this file are subject to the Sun Public License * Version 1.0 (the "License"). You may not use this file except in * compliance with the License. A copy of the License is available at * http://www.sun.com/ * * The Original Code is NetBeans. The Initial Developer of the Original * Code is Sun Microsystems, Inc. Portions Copyright 1997-2002 Sun * Microsystems, Inc. All Rights Reserved. */ package org.netbeans.modules.xml.text.syntax.javacc.lib; /** * This interface describes a character stream that maintains line and * column number positions of the characters. It also has the capability * to backup the stream to some extent. An implementation of this * interface is used in the TokenManager implementation generated by * JavaCCParser. * * All the methods except backup can be implemented in any fashion. backup * needs to be implemented correctly for the correct operation of the lexer. * Rest of the methods are all used to get information like line number, * column number and the String that constitutes a token and are not used * by the lexer. Hence their implementation won't affect the generated lexer's * operation. */ public interface CharStream { /** * Returns the next character from the selected input. The method * of selecting the input is the responsibility of the class * implementing this interface. Can throw any java.io.IOException. */ abstract public char readChar() throws java.io.IOException; /** * Returns the column position of the character last read. * @deprecated * @see #getEndColumn */ abstract public int getColumn(); /** * Returns the line number of the character last read. * @deprecated * @see #getEndLine */ abstract public int getLine(); /** * Returns the column number of the last character for current token (being * matched after the last call to BeginTOken). */ abstract public int getEndColumn(); /** * Returns the line number of the last character for current token (being * matched after the last call to BeginTOken). */ abstract public int getEndLine(); /** * Returns the column number of the first character for current token (being * matched after the last call to BeginTOken). */ abstract public int getBeginColumn(); /** * Returns the line number of the first character for current token (being * matched after the last call to BeginTOken). */ abstract public int getBeginLine(); /** * Backs up the input stream by amount steps. Lexer calls this method if it * had already read some characters, but could not use them to match a * (longer) token. So, they will be used again as the prefix of the next * token and it is the implemetation's responsibility to do this right. */ abstract public void backup(int amount); /** * Returns the next character that marks the beginning of the next token. * All characters must remain in the buffer between two successive calls * to this method to implement backup correctly. */ abstract public char BeginToken() throws java.io.IOException; /** * Returns a string made up of characters from the marked token beginning * to the current buffer position. Implementations have the choice of returning * anything that they want to. For example, for efficiency, one might decide * to just return null, which is a valid implementation. */ abstract public String GetImage(); /** * Returns an array of characters that make up the suffix of length 'len' for * the currently matched token. This is used to build up the matched string * for use in actions in the case of MORE. A simple and inefficient * implementation of this is as follows : * * { * String t = GetImage(); * return t.substring(t.length() - len, t.length()).toCharArray(); * } */ abstract public char[] GetSuffix(int len); /** * The lexer calls this function to indicate that it is done with the stream * and hence implementations can free any resources held by this class. * Again, the body of this function can be just empty and it will not * affect the lexer's operation. */ abstract public void Done(); } |
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