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git.zerfleddert.de Git - proxmark3-svn/blob - common/crc.c
1 //-----------------------------------------------------------------------------
2 // This code is licensed to you under the terms of the GNU GPL, version 2 or,
3 // at your option, any later version. See the LICENSE.txt file for the text of
5 //-----------------------------------------------------------------------------
6 // Generic CRC calculation code.
7 //-----------------------------------------------------------------------------
12 void crc_init(crc_t
*crc
, int order
, uint32_t polynom
, uint32_t initial_value
, uint32_t final_xor
)
15 crc
->polynom
= polynom
;
16 crc
->initial_value
= initial_value
;
17 crc
->final_xor
= final_xor
;
18 crc
->mask
= (1L<<order
)-1;
22 void crc_update(crc_t
*crc
, uint32_t data
, int data_width
)
25 for(i
=0; i
<data_width
; i
++) {
26 int oldstate
= crc
->state
;
27 crc
->state
= crc
->state
>> 1;
28 if( (oldstate
^data
) & 1 ) {
29 crc
->state
^= crc
->polynom
;
35 void crc_clear(crc_t
*crc
)
37 crc
->state
= crc
->initial_value
& crc
->mask
;
40 uint32_t crc_finish(crc_t
*crc
)
42 return ( crc
->state
^ crc
->final_xor
) & crc
->mask
;
46 uint32_t CRC8Maxim(uint8_t *buff
, size_t size
)
49 crc_init(&crc
, 9, 0x8c, 0x00, 0x00);
52 for (size_t i
=0; i
< size
; ++i
){
53 crc_update(&crc
, buff
[i
], 8);
55 return crc_finish(&crc
);