#include “util.h”
uint32_t crc32_for_byte(uint32_t r) {
for(int j = 0; j < 8; ++j)
r = (r & 1? 0: (uint32_t)0xEDB88320L) ^ r >> 1;
return r ^ (uint32_t)0xFF000000L;
}
void crc32(const void *data, size_t n_bytes, uint32_t* crc) {
static uint32_t table[0x100];
if(!*table)
for(size_t i = 0; i < 0x100; ++i)
table[i] = crc32_for_byte(i);
for(size_t i = 0; i < n_bytes; ++i)
*crc = table[(uint8_t)*crc ^ ((uint8_t*)data)[i]] ^ *crc >> 8;
}
uint32_t compute_checksum(const void* pkt, size_t n_bytes) {
uint32_t crc = 0;
crc32(pkt, n_bytes, &crc);
return crc;
}