|
Last change
on this file since 212 was 2, checked in by Rick van der Zwet, 15 years ago |
|
Initial import of data of old repository ('data') worth keeping (e.g. tracking
means of URL access statistics)
|
-
Property svn:executable
set to
*
|
|
File size:
2.2 KB
|
| Line | |
|---|
| 1 | #include "lib_crc.h"
|
|---|
| 2 | #define P_32 0xEDB88320L
|
|---|
| 3 |
|
|---|
| 4 | static int crc_tab32_init = FALSE;
|
|---|
| 5 |
|
|---|
| 6 | static unsigned long crc_tab32[256];
|
|---|
| 7 |
|
|---|
| 8 |
|
|---|
| 9 | static void init_crc32_tab( void );
|
|---|
| 10 |
|
|---|
| 11 |
|
|---|
| 12 | /*******************************************************************\
|
|---|
| 13 | * *
|
|---|
| 14 | * unsigned long update_crc_32( unsigned long crc, char c ); *
|
|---|
| 15 | * *
|
|---|
| 16 | * The function update_crc_32 calculates a new CRC-32 value *
|
|---|
| 17 | * based on the previous value of the CRC and the next byte *
|
|---|
| 18 | * of the data to be checked. *
|
|---|
| 19 | * *
|
|---|
| 20 | \*******************************************************************/
|
|---|
| 21 |
|
|---|
| 22 | unsigned long update_crc_32( unsigned long crc, char c ) {
|
|---|
| 23 |
|
|---|
| 24 | unsigned long tmp, long_c;
|
|---|
| 25 |
|
|---|
| 26 | long_c = 0x000000ffL & (unsigned long) c;
|
|---|
| 27 |
|
|---|
| 28 | if ( ! crc_tab32_init ) init_crc32_tab();
|
|---|
| 29 |
|
|---|
| 30 | tmp = crc ^ long_c;
|
|---|
| 31 | crc = (crc >> 8) ^ crc_tab32[ tmp & 0xff ];
|
|---|
| 32 |
|
|---|
| 33 | return crc;
|
|---|
| 34 |
|
|---|
| 35 | } /* update_crc_32 */
|
|---|
| 36 |
|
|---|
| 37 |
|
|---|
| 38 | /*******************************************************************\
|
|---|
| 39 | * *
|
|---|
| 40 | * static void init_crc32_tab( void ); *
|
|---|
| 41 | * *
|
|---|
| 42 | * The function init_crc32_tab() is used to fill the array *
|
|---|
| 43 | * for calculation of the CRC-32 with values. *
|
|---|
| 44 | * *
|
|---|
| 45 | \*******************************************************************/
|
|---|
| 46 |
|
|---|
| 47 | static void init_crc32_tab( void ) {
|
|---|
| 48 |
|
|---|
| 49 | int i, j;
|
|---|
| 50 | unsigned long crc;
|
|---|
| 51 |
|
|---|
| 52 | for (i=0; i<256; i++) {
|
|---|
| 53 |
|
|---|
| 54 | crc = (unsigned long) i;
|
|---|
| 55 |
|
|---|
| 56 | for (j=0; j<8; j++) {
|
|---|
| 57 |
|
|---|
| 58 | if ( crc & 0x00000001L ) crc = ( crc >> 1 ) ^ P_32;
|
|---|
| 59 | else crc = crc >> 1;
|
|---|
| 60 | }
|
|---|
| 61 |
|
|---|
| 62 | crc_tab32[i] = crc;
|
|---|
| 63 | }
|
|---|
| 64 |
|
|---|
| 65 | crc_tab32_init = TRUE;
|
|---|
| 66 |
|
|---|
| 67 | } /* init_crc32_tab */
|
|---|
Note:
See
TracBrowser
for help on using the repository browser.
