1 /* 2 * Copyright (C) 2009,2010 Matthias Treydte <mt@waldheinz.de> 3 * 4 * This library is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU Lesser General Public License as published 6 * by the Free Software Foundation; either version 2.1 of the License, or 7 * (at your option) any later version. 8 * 9 * This library is distributed in the hope that it will be useful, but 10 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 11 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 12 * License for more details. 13 * 14 * You should have received a copy of the GNU Lesser General Public License 15 * along with this library; If not, write to the Free Software Foundation, Inc., 16 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 17 */ 18 19 package de.waldheinz.fs.fat; 20 21 import de.waldheinz.fs.BlockDevice; 22 import java.io.IOException; 23 import java.nio.ByteBuffer; 24 import java.nio.ByteOrder; 25 26 /** 27 * 28 * @author Matthias Treydte <waldheinz at gmail.com> 29 */ 30 class Sector { 31 private final BlockDevice device; 32 private final long offset; 33 34 /** 35 * The buffer holding the contents of this {@code Sector}. 36 */ 37 protected final ByteBuffer buffer; 38 39 private boolean dirty; 40 Sector(BlockDevice device, long offset, int size)41 protected Sector(BlockDevice device, long offset, int size) { 42 this.offset = offset; 43 this.device = device; 44 this.buffer = ByteBuffer.allocate(size); 45 this.buffer.order(ByteOrder.LITTLE_ENDIAN); 46 this.dirty = true; 47 } 48 49 /** 50 * Reads the contents of this {@code Sector} from the device into the 51 * internal buffer and resets the "dirty" state. 52 * 53 * @throws IOException on read error 54 * @see #isDirty() 55 */ read()56 protected void read() throws IOException { 57 buffer.rewind(); 58 buffer.limit(buffer.capacity()); 59 device.read(offset, buffer); 60 this.dirty = false; 61 } 62 isDirty()63 public final boolean isDirty() { 64 return this.dirty; 65 } 66 markDirty()67 protected final void markDirty() { 68 this.dirty = true; 69 } 70 71 /** 72 * Returns the {@code BlockDevice} where this {@code Sector} is stored. 73 * 74 * @return this {@code Sector}'s device 75 */ getDevice()76 public BlockDevice getDevice() { 77 return this.device; 78 } 79 write()80 public final void write() throws IOException { 81 if (!isDirty()) return; 82 83 buffer.position(0); 84 buffer.limit(buffer.capacity()); 85 device.write(offset, buffer); 86 this.dirty = false; 87 } 88 get16(int offset)89 protected int get16(int offset) { 90 return buffer.getShort(offset) & 0xffff; 91 } 92 get32(int offset)93 protected long get32(int offset) { 94 return buffer.getInt(offset) & 0xffffffff; 95 } 96 get8(int offset)97 protected int get8(int offset) { 98 return buffer.get(offset) & 0xff; 99 } 100 set16(int offset, int value)101 protected void set16(int offset, int value) { 102 buffer.putShort(offset, (short) (value & 0xffff)); 103 dirty = true; 104 } 105 set32(int offset, long value)106 protected void set32(int offset, long value) { 107 buffer.putInt(offset, (int) (value & 0xffffffff)); 108 dirty = true; 109 } 110 set8(int offset, int value)111 protected void set8(int offset, int value) { 112 if ((value & 0xff) != value) { 113 throw new IllegalArgumentException( 114 value + " too big to be stored in a single octet"); 115 } 116 117 buffer.put(offset, (byte) (value & 0xff)); 118 dirty = true; 119 } 120 121 /** 122 * Returns the device offset to this {@code Sector}. 123 * 124 * @return the {@code Sector}'s device offset 125 */ getOffset()126 protected long getOffset() { 127 return this.offset; 128 } 129 } 130