org.nfctools.mf.NxpCrc Maven / Gradle / Ivy
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/**
* Copyright 2011-2012 Adrian Stabiszewski, [email protected]
*
* 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.nfctools.mf;
public class NxpCrc {
public static final int CRC_PRESET = 0xc7; // docs example 0xc7; nokia: 0xe3
private int crc = CRC_PRESET;
public void add(int value) {
/* x^8 + x^4 + x^3 + x^2 + 1 => 0x11d */
int poly = 0x1d;
crc ^= value;
for (int currentBit = 7; currentBit >= 0; currentBit--) {
long bitOut = crc & 0x80;
crc <<= 1;
if (bitOut > 0)
crc ^= poly;
}
}
public void reset() {
crc = CRC_PRESET;
}
public byte getCrc() {
return (byte)crc;
}
}