62 lines
1.1 KiB
C
62 lines
1.1 KiB
C
|
/* oneC_sum() - One complement's checksum Author: Kees J. Bot
|
||
|
|
* 8 May 1995
|
||
|
|
* See RFC 1071, "Computing the Internet checksum"
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <sys/types.h>
|
||
|
|
#include <net/gen/oneCsum.h>
|
||
|
|
|
||
|
|
u16_t oneC_sum(u16_t prev, void *data, size_t size)
|
||
|
|
{
|
||
|
|
u8_t *dptr;
|
||
|
|
size_t n;
|
||
|
|
u16_t word;
|
||
|
|
u32_t sum;
|
||
|
|
int swap= 0;
|
||
|
|
|
||
|
|
sum= prev;
|
||
|
|
dptr= data;
|
||
|
|
n= size;
|
||
|
|
|
||
|
|
swap= ((size_t) dptr & 1);
|
||
|
|
if (swap) {
|
||
|
|
sum= ((sum & 0xFF) << 8) | ((sum & 0xFF00) >> 8);
|
||
|
|
if (n > 0) {
|
||
|
|
((u8_t *) &word)[0]= 0;
|
||
|
|
((u8_t *) &word)[1]= dptr[0];
|
||
|
|
sum+= (u32_t) word;
|
||
|
|
dptr+= 1;
|
||
|
|
n-= 1;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
while (n >= 8) {
|
||
|
|
sum+= (u32_t) ((u16_t *) dptr)[0]
|
||
|
|
+ (u32_t) ((u16_t *) dptr)[1]
|
||
|
|
+ (u32_t) ((u16_t *) dptr)[2]
|
||
|
|
+ (u32_t) ((u16_t *) dptr)[3];
|
||
|
|
dptr+= 8;
|
||
|
|
n-= 8;
|
||
|
|
}
|
||
|
|
|
||
|
|
while (n >= 2) {
|
||
|
|
sum+= (u32_t) ((u16_t *) dptr)[0];
|
||
|
|
dptr+= 2;
|
||
|
|
n-= 2;
|
||
|
|
}
|
||
|
|
|
||
|
|
if (n > 0) {
|
||
|
|
((u8_t *) &word)[0]= dptr[0];
|
||
|
|
((u8_t *) &word)[1]= 0;
|
||
|
|
sum+= (u32_t) word;
|
||
|
|
}
|
||
|
|
|
||
|
|
sum= (sum & 0xFFFF) + (sum >> 16);
|
||
|
|
if (sum > 0xFFFF) sum++;
|
||
|
|
|
||
|
|
if (swap) {
|
||
|
|
sum= ((sum & 0xFF) << 8) | ((sum & 0xFF00) >> 8);
|
||
|
|
}
|
||
|
|
return sum;
|
||
|
|
}
|