001/* 002 * gnu/regexp/CharIndexed.java 003 * Copyright (C) 1998-2001 Wes Biggs 004 * 005 * This library is free software; you can redistribute it and/or modify 006 * it under the terms of the GNU Lesser General Public License as published 007 * by the Free Software Foundation; either version 2.1 of the License, or 008 * (at your option) any later version. 009 * 010 * This library is distributed in the hope that it will be useful, 011 * but WITHOUT ANY WARRANTY; without even the implied warranty of 012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 013 * GNU Lesser General Public License for more details. 014 * 015 * You should have received a copy of the GNU Lesser General Public License 016 * along with this program; if not, write to the Free Software 017 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 018 */ 019package gnu.regexp; 020 021/** 022 * Defines the interface used internally so that different types of source 023 * text can be accessed in the same way. Built-in concrete classes provide 024 * support for String, StringBuffer, InputStream and char[] types. 025 * A class that is CharIndexed supports the notion of a cursor within a 026 * block of text. The cursor must be able to be advanced via the move() 027 * method. The charAt() method returns the character at the cursor position 028 * plus a given offset. 029 * 030 * @author <A HREF="mailto:wes@cacas.org">Wes Biggs</A> 031 */ 032public interface CharIndexed { 033 /** 034 * Defines a constant (0xFFFF was somewhat arbitrarily chosen) 035 * that can be returned by the charAt() function indicating that 036 * the specified index is out of range. 037 */ 038 char OUT_OF_BOUNDS = '\uFFFF'; 039 040 /** 041 * Returns the character at the given offset past the current cursor 042 * position in the input. The index of the current position is zero. 043 * It is possible for this method to be called with a negative index. 044 * This happens when using the '^' operator in multiline matching mode 045 * or the '\b' or '\<' word boundary operators. In any case, the lower 046 * bound is currently fixed at -2 (for '^' with a two-character newline). 047 * 048 * @param index the offset position in the character field to examine 049 * @return the character at the specified index, or the OUT_OF_BOUNDS 050 * character defined by this interface. 051 */ 052 char charAt(int index); 053 054 /** 055 * Shifts the input buffer by a given number of positions. Returns 056 * true if the new cursor position is valid. 057 */ 058 boolean move(int index); 059 060 /** 061 * Returns true if the most recent move() operation placed the cursor 062 * position at a valid position in the input. 063 */ 064 boolean isValid(); 065}