RfidResearchGroup/proxmark3
1
1
Fork 0
mirror of https://github.com/RfidResearchGroup/proxmark3.git synced 2025-01-28 02:50:21 +08:00
Code Issues Projects Releases Packages Wiki Activity

Add generic CRC calculation code

Browse source
This commit is contained in:
henryk@ploetzli.ch 2009-11-25 20:41:41 +00:00
parent c86cc30801
commit 68d9d60a4d
3 changed files with 90 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
armsrc/Makefile
View file

@ -25,7 +25,8 @@ THUMBSRC = start.c \
ARMSRC = fpgaloader.c \
legicrf.c \
$(SRC_ISO14443a) \
$(SRC_ISO14443b)
$(SRC_ISO14443b) \
crc.c
# Do not move this inclusion before the definition of {THUMB,ASM,ARM}SRC
include ../common/Makefile.common

41
common/crc.c Normal file
View file

@ -0,0 +1,41 @@
/*
* crc.c
*
* Generic CRC calculation code.
*
*/
#include "crc.h"
void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor)
{
crc->order = order;
crc->polynom = polynom;
crc->initial_value = initial_value;
crc->final_xor = final_xor;
crc->mask = (1L<<order)-1;
crc_clear(crc);
}
void crc_update(crc_t *crc, uint32_t data, int data_width)
{
int i;
for(i=0; i<data_width; i++) {
int oldstate = crc->state;
crc->state = crc->state >> 1;
if( (oldstate^data) & 1 ) {
crc->state ^= crc->polynom;
}
data >>= 1;
}
}
void crc_clear(crc_t *crc)
{
crc->state = crc->initial_value & crc->mask;
}
uint32_t crc_finish(crc_t *crc)
{
return ( crc->state ^ crc->final_xor ) & crc->mask;
}

47
include/crc.h Normal file
View file

@ -0,0 +1,47 @@
/*
* crc.h
*
* Generic CRC calculation code.
*
*/
#ifndef CRC_H_
#define CRC_H_
#include <stdint.h>
typedef struct crc {
uint32_t state;
int order;
uint32_t polynom;
uint32_t initial_value;
uint32_t final_xor;
uint32_t mask;
} crc_t;
/* Initialize a crc structure. order is the order of the polynom, e.g. 32 for a CRC-32
* polynom is the CRC polynom. initial_value is the initial value of a clean state.
* final_xor is XORed onto the state before returning it from crc_result(). */
extern void crc_init(crc_t *crc, int order, uint32_t polynom, uint32_t initial_value, uint32_t final_xor);
/* Update the crc state. data is the data of length data_width bits (only the the
* data_width lower-most bits are used).
*/
extern void crc_update(crc_t *crc, uint32_t data, int data_width);
/* Clean the crc state, e.g. reset it to initial_value */
extern void crc_clear(crc_t *crc);
/* Get the result of the crc calculation */
extern uint32_t crc_finish(crc_t *crc);
/* Static initialization of a crc structure */
#define CRC_INITIALIZER(_order, _polynom, _initial_value, _final_xor) { \
.state = ((_initial_value) & ((1L<<(_order))-1)), \
.order = (_order), \
.polynom = (_polynom), \
.initial_value = (_initial_value), \
.final_xor = (_final_xor), \
.mask = ((1L<<(_order))-1) }
#endif /* CRC_H_ */