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/*
* Copyright 2012 - 2018 Anton Tananaev (anton@traccar.org)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.traccar.helper;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.zip.CRC32;
public final class Checksum {
private Checksum() {
}
public static class Algorithm {
private final int poly;
private final int init;
private final boolean refIn;
private final boolean refOut;
private final int xorOut;
private final int[] table;
public Algorithm(int bits, int poly, int init, boolean refIn, boolean refOut, int xorOut) {
this.poly = poly;
this.init = init;
this.refIn = refIn;
this.refOut = refOut;
this.xorOut = xorOut;
this.table = bits == 8 ? initTable8() : initTable16();
}
private int[] initTable8() {
int[] table = new int[256];
int crc;
for (int i = 0; i < 256; i++) {
crc = i;
for (int j = 0; j < 8; j++) {
boolean bit = (crc & 0x80) != 0;
crc <<= 1;
if (bit) {
crc ^= poly;
}
}
table[i] = crc & 0xFF;
}
return table;
}
private int[] initTable16() {
int[] table = new int[256];
int crc;
for (int i = 0; i < 256; i++) {
crc = i << 8;
for (int j = 0; j < 8; j++) {
boolean bit = (crc & 0x8000) != 0;
crc <<= 1;
if (bit) {
crc ^= poly;
}
}
table[i] = crc & 0xFFFF;
}
return table;
}
}
private static int reverse(int value, int bits) {
int result = 0;
for (int i = 0; i < bits; i++) {
result = (result << 1) | (value & 1);
value >>= 1;
}
return result;
}
public static int crc8(Algorithm algorithm, ByteBuffer buf) {
int crc = algorithm.init;
while (buf.hasRemaining()) {
int b = buf.get() & 0xFF;
if (algorithm.refIn) {
b = reverse(b, 8);
}
crc = algorithm.table[(crc & 0xFF) ^ b];
}
if (algorithm.refOut) {
crc = reverse(crc, 8);
}
return (crc ^ algorithm.xorOut) & 0xFF;
}
public static int crc16(Algorithm algorithm, ByteBuffer buf) {
int crc = algorithm.init;
while (buf.hasRemaining()) {
int b = buf.get() & 0xFF;
if (algorithm.refIn) {
b = reverse(b, 8);
}
crc = (crc << 8) ^ algorithm.table[((crc >> 8) & 0xFF) ^ b];
}
if (algorithm.refOut) {
crc = reverse(crc, 16);
}
return (crc ^ algorithm.xorOut) & 0xFFFF;
}
public static final Algorithm CRC8_EGTS = new Algorithm(8, 0x31, 0xFF, false, false, 0x00);
public static final Algorithm CRC8_ROHC = new Algorithm(8, 0x07, 0xFF, true, true, 0x00);
public static final Algorithm CRC16_IBM = new Algorithm(16, 0x8005, 0x0000, true, true, 0x0000);
public static final Algorithm CRC16_X25 = new Algorithm(16, 0x1021, 0xFFFF, true, true, 0xFFFF);
public static final Algorithm CRC16_MODBUS = new Algorithm(16, 0x8005, 0xFFFF, true, true, 0x0000);
public static final Algorithm CRC16_CCITT_FALSE = new Algorithm(16, 0x1021, 0xFFFF, false, false, 0x0000);
public static final Algorithm CRC16_KERMIT = new Algorithm(16, 0x1021, 0x0000, true, true, 0x0000);
public static final Algorithm CRC16_XMODEM = new Algorithm(16, 0x1021, 0x0000, false, false, 0x0000);
public static int crc32(ByteBuffer buf) {
CRC32 checksum = new CRC32();
while (buf.hasRemaining()) {
checksum.update(buf.get());
}
return (int) checksum.getValue();
}
public static int xor(ByteBuffer buf) {
int checksum = 0;
while (buf.hasRemaining()) {
checksum ^= buf.get();
}
return checksum;
}
public static int xor(String string) {
byte checksum = 0;
for (byte b : string.getBytes(StandardCharsets.US_ASCII)) {
checksum ^= b;
}
return checksum;
}
public static String nmea(String string) {
return String.format("*%02X", xor(string));
}
public static int sum(ByteBuffer buf) {
byte checksum = 0;
while (buf.hasRemaining()) {
checksum += buf.get();
}
return checksum;
}
public static int modulo256(ByteBuffer buf) {
int checksum = 0;
while (buf.hasRemaining()) {
checksum = (checksum + buf.get()) & 0xFF;
}
return checksum;
}
public static String sum(String msg) {
byte checksum = 0;
for (byte b : msg.getBytes(StandardCharsets.US_ASCII)) {
checksum += b;
}
return String.format("%02X", checksum).toUpperCase();
}
public static long luhn(long imei) {
long checksum = 0;
long remain = imei;
for (int i = 0; remain != 0; i++) {
long digit = remain % 10;
if (i % 2 == 0) {
digit *= 2;
if (digit >= 10) {
digit = 1 + (digit % 10);
}
}
checksum += digit;
remain /= 10;
}
return (10 - (checksum % 10)) % 10;
}
}
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