/jEdit/tags/jedit-4-0-pre5/gnu/regexp/CharIndexedReader.java

  1/*
  2 *  gnu/regexp/CharIndexedReader.java
  3 *  Copyright (C) 2001 Lee Sau Dan
  4 *  Based on gnu.regexp.CharIndexedInputStream by Wes Biggs
  5 *
  6 *  This library is free software; you can redistribute it and/or modify
  7 *  it under the terms of the GNU Lesser General Public License as published
  8 *  by the Free Software Foundation; either version 2.1 of the License, or
  9 *  (at your option) any later version.
 10 *
 11 *  This library is distributed in the hope that it will be useful,
 12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 14 *  GNU Lesser General Public License for more details.
 15 *
 16 *  You should have received a copy of the GNU Lesser General Public License
 17 *  along with this program; if not, write to the Free Software
 18 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 19 */
 20
 21package gnu.regexp;
 22import java.io.Reader;
 23import java.io.BufferedReader;
 24import java.io.IOException;
 25
 26// TODO: move(x) shouldn't rely on calling next() x times
 27
 28class CharIndexedReader implements CharIndexed {
 29    private static final int BUFFER_INCREMENT = 1024;
 30    private static final int UNKNOWN = Integer.MAX_VALUE; // value for end
 31    
 32    private final BufferedReader br;
 33    // so that we don't try to reset() right away
 34    private int index = -1;
 35
 36    private int bufsize = BUFFER_INCREMENT;
 37
 38    private int end = UNKNOWN;
 39
 40    private char cached = OUT_OF_BOUNDS;
 41
 42    // Big enough for a \r\n pair
 43    // lookBehind[0] = most recent
 44    // lookBehind[1] = second most recent
 45    private char[] lookBehind = new char[] { OUT_OF_BOUNDS, OUT_OF_BOUNDS }; 
 46  
 47    CharIndexedReader(Reader reader, int index) {
 48	if (reader instanceof BufferedReader) {
 49	    br = (BufferedReader) reader; 
 50	} else {
 51	    br = new BufferedReader(reader,BUFFER_INCREMENT);
 52	}
 53	next();
 54	if (index > 0) move(index);
 55    }
 56    
 57    private boolean next() {
 58	lookBehind[1] = lookBehind[0];
 59	lookBehind[0] = cached;
 60
 61	if (end == 1) {
 62	    cached = OUT_OF_BOUNDS;
 63	    return false;
 64	}
 65	end--; // closer to end
 66	
 67	try {
 68	    if (index != -1) {
 69		br.reset();
 70	    }
 71	    int i = br.read();
 72	    br.mark(bufsize);
 73	    if (i == -1) {
 74		end = 1;
 75		cached = OUT_OF_BOUNDS;
 76		return false;
 77	    }
 78
 79	    // convert the byte read into a char
 80	    cached = (char) i;
 81	    index = 1;
 82	} catch (IOException e) { 
 83	    e.printStackTrace();
 84	    cached = OUT_OF_BOUNDS;
 85	    return false; 
 86	}
 87	return true;
 88    }
 89    
 90    public char charAt(int index) {
 91	if (index == 0) {
 92	    return cached;
 93	} else if (index >= end) {
 94	    return OUT_OF_BOUNDS;
 95	} else if (index >= bufsize) {
 96	    // Allocate more space in the buffer.
 97	    try {
 98		while (bufsize <= index) bufsize += BUFFER_INCREMENT;
 99		br.reset();
100		br.mark(bufsize);
101		br.skip(index-1);
102	    } catch (IOException e) { }
103	} else if (this.index != index) {
104	    try {
105		br.reset();
106		br.skip(index-1);
107	    } catch (IOException e) { }
108	} else if (index == -1) {
109	    return lookBehind[0];
110	} else if (index == -2) {
111	    return lookBehind[1];
112	} else if (index < -2) {
113	    return OUT_OF_BOUNDS;
114	}
115
116	char ch = OUT_OF_BOUNDS;
117	
118	try {
119	    int i = br.read();
120	    this.index = index+1; // this.index is index of next pos relative to charAt(0)
121	    if (i == -1) {
122		// set flag that next should fail next time?
123		end = index;
124		return ch;
125	    }
126	    ch = (char) i;
127	} catch (IOException ie) { }
128	
129	return ch;
130    }
131    
132    public boolean move(int index) {
133	// move read position [index] clicks from 'charAt(0)'
134	boolean retval = true;
135	while (retval && (index-- > 0)) retval = next();
136	return retval;
137    }
138    
139    public boolean isValid() {
140	return (cached != OUT_OF_BOUNDS);
141    }
142}