8f4202db28
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@29936 a1c6a512-1295-4272-9138-f99709370657
35 lines
938 B
C
35 lines
938 B
C
#include <stdint.h>
|
|
#include "checksum.h"
|
|
|
|
uint16_t checksum(void *buff, uint32_t size)
|
|
{
|
|
uint32_t r2 = 0xffff;
|
|
uint32_t r3 = 0;
|
|
uint32_t i, j;
|
|
|
|
for (i=0; i<size; i++) {
|
|
r3 = 0x80;
|
|
for (j=0; j<8; j++) {
|
|
if ((r2 & 0x8000) != 0) {
|
|
r2 <<= 17;
|
|
r2 >>= 16;
|
|
r2 ^= 0x1000;
|
|
r2 ^= 0x21;
|
|
}
|
|
else {
|
|
r2 <<= 17;
|
|
r2 >>= 16;
|
|
}
|
|
|
|
if ((((uint8_t *)buff)[i] & r3) != 0) {
|
|
r2 ^= 0x1000;
|
|
r2 ^= 0x21;
|
|
}
|
|
|
|
r3 >>= 1;
|
|
}
|
|
}
|
|
|
|
return r2 & 0xffff;
|
|
}
|
|
|