1 /* 2 * Copyright (C) 2003-2009 JNode.org 3 * 2009,2010 Matthias Treydte <mt@waldheinz.de> 4 * 5 * This library is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU Lesser General Public License as published 7 * by the Free Software Foundation; either version 2.1 of the License, or 8 * (at your option) any later version. 9 * 10 * This library is distributed in the hope that it will be useful, but 11 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 12 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 13 * License for more details. 14 * 15 * You should have received a copy of the GNU Lesser General Public License 16 * along with this library; If not, write to the Free Software Foundation, Inc., 17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 18 */ 19 20 package de.waldheinz.fs.fat; 21 22 23 /** 24 * Little endian (LSB first) conversion methods. 25 * 26 * @author Ewout Prangsma <epr at users.sourceforge.net> 27 */ 28 final class LittleEndian { 29 LittleEndian()30 private LittleEndian() { /* no instances */ } 31 32 /** 33 * Gets an 8-bit unsigned integer from the given byte array at 34 * the given offset. 35 * 36 * @param src the byte offset where to read the value from 37 * @param offset the byte array to extract the value from 38 * @return the integer that was read 39 */ getUInt8(byte[] src, int offset)40 public static int getUInt8(byte[] src, int offset) { 41 return src[offset] & 0xFF; 42 } 43 44 /** 45 * Gets a 16-bit unsigned integer from the given byte array at the given offset. 46 * 47 * @param src 48 * @param offset 49 */ getUInt16(byte[] src, int offset)50 public static int getUInt16(byte[] src, int offset) { 51 final int v0 = src[offset + 0] & 0xFF; 52 final int v1 = src[offset + 1] & 0xFF; 53 return ((v1 << 8) | v0); 54 } 55 56 /** 57 * Gets a 32-bit unsigned integer from the given byte array at the given offset. 58 * 59 * @param src 60 * @param offset 61 */ getUInt32(byte[] src, int offset)62 public static long getUInt32(byte[] src, int offset) { 63 final long v0 = src[offset + 0] & 0xFF; 64 final long v1 = src[offset + 1] & 0xFF; 65 final long v2 = src[offset + 2] & 0xFF; 66 final long v3 = src[offset + 3] & 0xFF; 67 return ((v3 << 24) | (v2 << 16) | (v1 << 8) | v0); 68 } 69 70 /** 71 * Sets an 8-bit integer in the given byte array at the given offset. 72 */ setInt8(byte[] dst, int offset, int value)73 public static void setInt8(byte[] dst, int offset, int value) { 74 dst[offset] = (byte) value; 75 } 76 77 /** 78 * Sets a 16-bit integer in the given byte array at the given offset. 79 */ setInt16(byte[] dst, int offset, int value)80 public static void setInt16(byte[] dst, int offset, int value) { 81 dst[offset + 0] = (byte) (value & 0xFF); 82 dst[offset + 1] = (byte) ((value >>> 8) & 0xFF); 83 } 84 85 /** 86 * Sets a 32-bit integer in the given byte array at the given offset. 87 */ setInt32(byte[] dst, int offset, long value)88 public static void setInt32(byte[] dst, int offset, long value) 89 throws IllegalArgumentException { 90 91 if (value > Integer.MAX_VALUE) { 92 throw new IllegalArgumentException( 93 value + " can not be represented in a 32bit dword"); 94 } 95 96 dst[offset + 0] = (byte) (value & 0xFF); 97 dst[offset + 1] = (byte) ((value >>> 8) & 0xFF); 98 dst[offset + 2] = (byte) ((value >>> 16) & 0xFF); 99 dst[offset + 3] = (byte) ((value >>> 24) & 0xFF); 100 } 101 102 } 103