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/*
* 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 times
class 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);
}
}
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