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#include <stdarg.h>
#include <stdint.h>
#include <stdlib.h>
// based on code from RFCs 1071 and 1624
/*
static inline uint16_t csum_update(const void *ptr, uint16_t new_value, uint16_t wsum) {
uint32_t sum = *(uint16_t *)ptr + (~ntohs(*(uint16_t *)&new_value) & 0xffff) + ntohs(wsum);
sum = (sum & 0xffff) + (sum >> 16);
return htons(sum + (sum >> 16));
}
static inline uint16_t fold_sum(uint32_t sum) {
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return sum;
}
static inline uint16_t do_csum(const void *ptr, size_t len) {
uint32_t sum = 0;
while (len > 1) {
sum += *(uint16_t *)ptr++;
len -= 2;
}
if (len > 0)
sum += *(uint8_t *)ptr;
return ~fold_sum(sum);
}
static inline uint16_t csum_partial(uint16_t sum, const void *ptr, size_t len, ...) {
va_list ap;
va_start(ap, len);
do {
sum = ~fold_sum(~sum + ~do_csum(ptr, len));
} while ((ptr = va_arg(ap, const void *)) && (len = va_arg(ap, size_t)));
va_end(ap);
return sum;
}
*/
uint16_t csum_partial(const void *buff, int len, uint16_t wsum);
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