Modified kermit crc to use existing crc calc code

diff --git a/client/cmddata.c b/client/cmddata.c
index e85b3a6cc2f979551e9da3e5b47de2ff968f899c..cf105f88b993b216741720d675d8cfcbfda3c78d 100644 (file)
--- a/client/cmddata.c
+++ b/client/cmddata.c
@@ -1515,14 +1515,13 @@ int CmdFDXBdemodBI(const char *Cmd){
        uint32_t crc16 = bytebits_to_byteLSBF(BitStream+64,16);
        uint32_t extended = bytebits_to_byteLSBF(BitStream+80,24);
 
-       uint64_t rawid = ((uint64_t)bytebits_to_byteLSBF(BitStream,32)<<32) | bytebits_to_byteLSBF(BitStream+32,32);
+       uint64_t rawid = ((uint64_t)bytebits_to_byte(BitStream,32)<<32) | bytebits_to_byte(BitStream+32,32);
        uint8_t raw[8];
        num_to_bytes(rawid, 8, raw);
-       uint8_t *raw_ptr = SwapEndian64(raw, 8, 4);
 
-       if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(raw_ptr,8));
+       if (g_debugMode) PrintAndLog("Raw ID Hex: %s", sprint_hex(raw,8));
 
-       uint16_t calcCrc = crc16_ccitt_kermit(raw_ptr, 8);
+       uint16_t calcCrc = crc16_ccitt_kermit(raw, 8);
        PrintAndLog("Animal ID:     %04u-%012llu", countryCode, NationalCode);
        PrintAndLog("National Code: %012llu", NationalCode);
        PrintAndLog("CountryCode:   %04u", countryCode);

diff --git a/common/crc16.c b/common/crc16.c
index d48df3b2c9f650720c1a4c39810010ce4f8ded44..a37f1d7e35f69e63e6fba2259f0a011b8f1bf4ec 100644 (file)
--- a/common/crc16.c
+++ b/common/crc16.c
@@ -8,7 +8,6 @@
 
 #include "crc16.h"
 
-
 unsigned short update_crc16( unsigned short crc, unsigned char c )
 {
        unsigned short i, v, tcrc = 0;
@@ -44,16 +43,19 @@ uint16_t crc16_ccitt(uint8_t const *message, int length) {
 }
 
 uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) {
-       if (length == 0) return 0;
-       uint32_t crc = 0, q = 0;
-       uint8_t c;
-
-       for (int i = 0; i < length; i++){
-               c = message[i];
-               q = (crc ^ c ) & 0xF;
-               crc = (crc >> 4) ^ (q * 0x1081);
-               q = (crc ^ (c >> 4)) & 0xF;
-               crc = (crc >> 4) ^ (q * 0x1081);
-       }
-       return crc;
+       return bit_reverse_uint16(crc16(message, length, 0x0000, 0x1021));
+}
+
+uint16_t bit_reverse_uint16 (uint16_t value) {
+       const uint16_t mask0 = 0x5555;
+       const uint16_t mask1 = 0x3333;
+       const uint16_t mask2 = 0x0F0F;
+       const uint16_t mask3 = 0x00FF;
+
+       value = (((~mask0) & value) >> 1) | ((mask0 & value) << 1);
+       value = (((~mask1) & value) >> 2) | ((mask1 & value) << 2);
+       value = (((~mask2) & value) >> 4) | ((mask2 & value) << 4);
+       value = (((~mask3) & value) >> 8) | ((mask3 & value) << 8);
+
+       return value;
 }

diff --git a/common/crc16.h b/common/crc16.h
index 3656ce278c7b97ab4a8da3c6c0fdb20157196f93..8eb4befbcf1d7566cf0d7f8f73c370f29080e0ba 100644 (file)
--- a/common/crc16.h
+++ b/common/crc16.h
@@ -13,4 +13,5 @@ unsigned short update_crc16(unsigned short crc, unsigned char c);
 uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t polynomial);
 uint16_t crc16_ccitt(uint8_t const *message, int length);
 uint16_t crc16_ccitt_kermit(uint8_t const *message, int length);
+uint16_t bit_reverse_uint16 (uint16_t value);
 #endif