X-Git-Url: https://git.zerfleddert.de/cgi-bin/gitweb.cgi/proxmark3-svn/blobdiff_plain/ae6ead3dc84acd074be24c0da5efd94ea7a0b225..5636ee8ce6c74cd49ea204c838b77115c5a144e1:/common/crc16.c?ds=sidebyside diff --git a/common/crc16.c b/common/crc16.c index 973cd103..07090fc6 100644 --- a/common/crc16.c +++ b/common/crc16.c @@ -7,7 +7,7 @@ //----------------------------------------------------------------------------- #include "crc16.h" - +#define CRC16_MASK_CCITT 0x1021 unsigned short update_crc16( unsigned short crc, unsigned char c ) { @@ -41,5 +41,22 @@ uint16_t crc16(uint8_t const *message, int length, uint16_t remainder, uint16_t } uint16_t crc16_ccitt(uint8_t const *message, int length) { - return crc16(message, length, 0xffff, 0x1021); + return crc16(message, length, 0xffff, CRC16_MASK_CCITT); +} + +uint16_t crc16_ccitt_kermit(uint8_t const *message, int length) { + return bit_reverse_uint16(crc16(message, length, 0x0000, CRC16_MASK_CCITT)); +} +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; }