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48 lines
1.6 KiB
C
48 lines
1.6 KiB
C
//-----------------------------------------------------------------------------
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// This code is licensed to you under the terms of the GNU GPL, version 2 or,
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// at your option, any later version. See the LICENSE.txt file for the text of
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// the license.
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//-----------------------------------------------------------------------------
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// ISO14443 CRC calculation code.
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//-----------------------------------------------------------------------------
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#include "iso14443crc.h"
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static unsigned short UpdateCrc14443(unsigned char ch, unsigned short *lpwCrc)
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{
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ch = (ch ^ (unsigned char) ((*lpwCrc) & 0x00FF));
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ch = (ch ^ (ch << 4));
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*lpwCrc = (*lpwCrc >> 8) ^ ((unsigned short) ch << 8) ^
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((unsigned short) ch << 3) ^ ((unsigned short) ch >> 4);
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return (*lpwCrc);
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}
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void ComputeCrc14443(int CrcType,
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const unsigned char *Data, int Length,
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unsigned char *TransmitFirst,
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unsigned char *TransmitSecond)
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{
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unsigned char chBlock;
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unsigned short wCrc=CrcType;
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do {
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chBlock = *Data++;
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UpdateCrc14443(chBlock, &wCrc);
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} while (--Length);
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if (CrcType == CRC_14443_B)
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wCrc = ~wCrc; /* ISO/IEC 13239 (formerly ISO/IEC 3309) */
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*TransmitFirst = (unsigned char) (wCrc & 0xFF);
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*TransmitSecond = (unsigned char) ((wCrc >> 8) & 0xFF);
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return;
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}
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int CheckCrc14443(int CrcType, const unsigned char *Data, int Length) {
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unsigned char b1;
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unsigned char b2;
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if (Length < 3) return 0;
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ComputeCrc14443(CrcType, Data, Length - 2, &b1, &b2);
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if ((b1 == Data[Length - 2]) && (b2 == Data[Length - 1])) return 1;
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return 0;
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}
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