libnfc 1.4.2
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00001 /*- 00002 * Public platform independent Near Field Communication (NFC) library 00003 * 00004 * Copyright (C) 2009, Roel Verdult 00005 * 00006 * This program is free software: you can redistribute it and/or modify it 00007 * under the terms of the GNU Lesser General Public License as published by the 00008 * Free Software Foundation, either version 3 of the License, or (at your 00009 * option) any later version. 00010 * 00011 * This program is distributed in the hope that it will be useful, but WITHOUT 00012 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 00013 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for 00014 * more details. 00015 * 00016 * You should have received a copy of the GNU Lesser General Public License 00017 * along with this program. If not, see <http://www.gnu.org/licenses/> 00018 */ 00019 00025 #ifdef HAVE_CONFIG_H 00026 # include "config.h" 00027 #endif // HAVE_CONFIG_H 00028 00029 #include <stdio.h> 00030 00031 #include <nfc/nfc.h> 00032 00033 void 00034 iso14443a_crc (byte_t * pbtData, size_t szLen, byte_t * pbtCrc) 00035 { 00036 byte_t bt; 00037 uint32_t wCrc = 0x6363; 00038 00039 do { 00040 bt = *pbtData++; 00041 bt = (bt ^ (byte_t) (wCrc & 0x00FF)); 00042 bt = (bt ^ (bt << 4)); 00043 wCrc = (wCrc >> 8) ^ ((uint32_t) bt << 8) ^ ((uint32_t) bt << 3) ^ ((uint32_t) bt >> 4); 00044 } while (--szLen); 00045 00046 *pbtCrc++ = (byte_t) (wCrc & 0xFF); 00047 *pbtCrc = (byte_t) ((wCrc >> 8) & 0xFF); 00048 } 00049 00050 void 00051 iso14443a_crc_append (byte_t * pbtData, size_t szLen) 00052 { 00053 iso14443a_crc (pbtData, szLen, pbtData + szLen); 00054 } 00055 00056 byte_t * 00057 iso14443a_locate_historical_bytes(byte_t * pbtAts, size_t szAts, size_t * pszTk) 00058 { 00059 if (szAts) { 00060 size_t offset = 1; 00061 if (pbtAts[0] & 0x10) { // TA 00062 offset++; 00063 } 00064 if (pbtAts[0] & 0x20) { // TB 00065 offset++; 00066 } 00067 if (pbtAts[0] & 0x40) { // TC 00068 offset++; 00069 } 00070 if (szAts > offset) { 00071 *pszTk = (szAts-offset); 00072 return (pbtAts+offset); 00073 } 00074 } 00075 *pszTk = 0; 00076 return NULL; 00077 }