/*
* $Id$
*
* Copyright (C) 2003-2014 JNode.org
*
* 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 library; If not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
package org.jnode.fs.ext2;
import org.jnode.fs.FileSystemException;
/**
* This class provides static methods that operate on the data as a bitmap
*
* @author Andras Nagy
*/
public class FSBitmap {
private static final boolean DEBUG = true;
/**
* Check if the block/inode is free according to the bitmap.
*
* @param index the index of the block/inode relative to the block group
* (not relative to the whole fs)
* @return true if the block/inode is free, false otherwise
*/
protected static boolean isFree(byte[] data, int index) {
int byteIndex = index / 8;
byte bitIndex = (byte) (index % 8);
byte mask = (byte) (1 << bitIndex);
return ((data[byteIndex] & mask) == 0) ? true : false;
}
protected static boolean isFree(byte data, int index) {
// byte bitIndex = (byte) (index % 8);
byte mask = (byte) (1 << index);
return ((data & mask) == 0) ? true : false;
}
protected static void setBit(byte[] data, int index) {
int byteIndex = index / 8;
byte bitIndex = (byte) (index % 8);
byte mask = (byte) (1 << bitIndex);
data[byteIndex] = (byte) (data[byteIndex] | mask);
}
protected static void setBit(byte[] data, int byteIndex, int bitIndex) {
byte mask = (byte) (1 << bitIndex);
data[byteIndex] = (byte) (data[byteIndex] | mask);
}
protected static void freeBit(byte[] data, int index) throws FileSystemException {
int byteIndex = index / 8;
byte bitIndex = (byte) (index % 8);
byte mask = (byte) ~(1 << bitIndex);
// filesystem consistency check
if (DEBUG) {
if (isFree(data[byteIndex], bitIndex))
throw new FileSystemException("FS consistency error: you are trying "
+ "to free an unallocated block/inode");
}
data[byteIndex] = (byte) (data[byteIndex] & mask);
}
}