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/*
* Copyright (C) 2009,2010 Matthias Treydte <mt@waldheinz.de>
*
* 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 de.waldheinz.fs.fat;
import de.waldheinz.fs.BlockDevice;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
/**
*
* @author Matthias Treydte <waldheinz at gmail.com>
*/
class Sector {
private final BlockDevice device;
private final long offset;
/**
* The buffer holding the contents of this {@code Sector}.
*/
protected final ByteBuffer buffer;
private boolean dirty;
protected Sector(BlockDevice device, long offset, int size) {
this.offset = offset;
this.device = device;
this.buffer = ByteBuffer.allocate(size);
this.buffer.order(ByteOrder.LITTLE_ENDIAN);
this.dirty = true;
}
/**
* Reads the contents of this {@code Sector} from the device into the
* internal buffer and resets the "dirty" state.
*
* @throws IOException on read error
* @see #isDirty()
*/
protected void read() throws IOException {
buffer.rewind();
buffer.limit(buffer.capacity());
device.read(offset, buffer);
this.dirty = false;
}
public final boolean isDirty() {
return this.dirty;
}
protected final void markDirty() {
this.dirty = true;
}
/**
* Returns the {@code BlockDevice} where this {@code Sector} is stored.
*
* @return this {@code Sector}'s device
*/
public BlockDevice getDevice() {
return this.device;
}
public final void write() throws IOException {
if (!isDirty()) return;
buffer.position(0);
buffer.limit(buffer.capacity());
device.write(offset, buffer);
this.dirty = false;
}
protected int get16(int offset) {
return buffer.getShort(offset) & 0xffff;
}
protected long get32(int offset) {
return buffer.getInt(offset) & 0xffffffff;
}
protected int get8(int offset) {
return buffer.get(offset) & 0xff;
}
protected void set16(int offset, int value) {
buffer.putShort(offset, (short) (value & 0xffff));
dirty = true;
}
protected void set32(int offset, long value) {
buffer.putInt(offset, (int) (value & 0xffffffff));
dirty = true;
}
protected void set8(int offset, int value) {
if ((value & 0xff) != value) {
throw new IllegalArgumentException(
value + " too big to be stored in a single octet");
}
buffer.put(offset, (byte) (value & 0xff));
dirty = true;
}
/**
* Returns the device offset to this {@code Sector}.
*
* @return the {@code Sector}'s device offset
*/
protected long getOffset() {
return this.offset;
}
}
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