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45 lines
1.5 KiB
C
45 lines
1.5 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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uint16_t UpdateCrc14443(uint8_t b, uint16_t *crc) {
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b = (b ^ (uint8_t)((*crc) & 0x00FF));
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b = (b ^ (b << 4));
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*crc = (*crc >> 8) ^ ((uint16_t) b << 8) ^ ((uint16_t) b << 3) ^ ((uint16_t) b >> 4);
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return (*crc);
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}
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void ComputeCrc14443(uint16_t CrcType, const uint8_t *data, int length,
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uint8_t *TransmitFirst, uint8_t *TransmitSecond) {
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uint8_t b;
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uint16_t crc = CrcType;
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do {
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b = *data++;
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UpdateCrc14443(b, &crc);
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} while (--length);
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if (CrcType == CRC_14443_B)
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crc = ~crc; /* ISO/IEC 13239 (formerly ISO/IEC 3309) */
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*TransmitFirst = (uint8_t)(crc & 0xFF);
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*TransmitSecond = (uint8_t)((crc >> 8) & 0xFF);
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return;
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}
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bool CheckCrc14443(uint16_t CrcType, const uint8_t *data, int length) {
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if (length < 3) return false;
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uint8_t b1, b2;
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ComputeCrc14443(CrcType, data, length - 2, &b1, &b2);
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if ((b1 == data[length - 2]) && (b2 == data[length - 1]))
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return true;
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return false;
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}
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