/* *  gnu/regexp/CharIndexedReader.java *  Copyright (C) 2001 Lee Sau Dan *  Based on gnu.regexp.CharIndexedInputStream by Wes Biggs * *  This library is free software; you can redistribute it and/or modify *  it under the terms of the GNU Lesser General Public License as published *  by the Free Software Foundation; either version 2.1 of the License, or *  (at your option) any later version. * *  This library is distributed in the hope that it will be useful, *  but WITHOUT ANY WARRANTY; without even the implied warranty of *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the *  GNU Lesser General Public License for more details. * *  You should have received a copy of the GNU Lesser General Public License *  along with this program; if not, write to the Free Software *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */package gnu.regexp;import java.io.Reader;import java.io.BufferedReader;import java.io.IOException;// TODO: move(x) shouldn't rely on calling next() x timesclass CharIndexedReader implements CharIndexed {    private static final int BUFFER_INCREMENT = 1024;    private static final int UNKNOWN = Integer.MAX_VALUE; // value for end        private final BufferedReader br;    // so that we don't try to reset() right away    private int index = -1;    private int bufsize = BUFFER_INCREMENT;    private int end = UNKNOWN;    private char cached = OUT_OF_BOUNDS;    // Big enough for a \r\n pair    // lookBehind[0] = most recent    // lookBehind[1] = second most recent    private char[] lookBehind = new char[] { OUT_OF_BOUNDS, OUT_OF_BOUNDS };       CharIndexedReader(Reader reader, int index) {	if (reader instanceof BufferedReader) {	    br = (BufferedReader) reader; 	} else {	    br = new BufferedReader(reader,BUFFER_INCREMENT);	}	next();	if (index > 0) move(index);    }        private boolean next() {	lookBehind[1] = lookBehind[0];	lookBehind[0] = cached;	if (end == 1) {	    cached = OUT_OF_BOUNDS;	    return false;	}	end--; // closer to end		try {	    if (index != -1) {		br.reset();	    }	    int i = br.read();	    br.mark(bufsize);	    if (i == -1) {		end = 1;		cached = OUT_OF_BOUNDS;		return false;	    }	    // convert the byte read into a char	    cached = (char) i;	    index = 1;	} catch (IOException e) { 	    e.printStackTrace();	    cached = OUT_OF_BOUNDS;	    return false; 	}	return true;    }        public char charAt(int index) {	if (index == 0) {	    return cached;	} else if (index >= end) {	    return OUT_OF_BOUNDS;	} else if (index >= bufsize) {	    // Allocate more space in the buffer.	    try {		while (bufsize <= index) bufsize += BUFFER_INCREMENT;		br.reset();		br.mark(bufsize);		br.skip(index-1);	    } catch (IOException e) { }	} else if (this.index != index) {	    try {		br.reset();		br.skip(index-1);	    } catch (IOException e) { }	} else if (index == -1) {	    return lookBehind[0];	} else if (index == -2) {	    return lookBehind[1];	} else if (index < -2) {	    return OUT_OF_BOUNDS;	}	char ch = OUT_OF_BOUNDS;		try {	    int i = br.read();	    this.index = index+1; // this.index is index of next pos relative to charAt(0)	    if (i == -1) {		// set flag that next should fail next time?		end = index;		return ch;	    }	    ch = (char) i;	} catch (IOException ie) { }		return ch;    }        public boolean move(int index) {	// move read position [index] clicks from 'charAt(0)'	boolean retval = true;	while (retval && (index-- > 0)) retval = next();	return retval;    }        public boolean isValid() {	return (cached != OUT_OF_BOUNDS);    }}