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#include <resolv.h>
#include <string.h>
#define BITOP(a,b,op) \
((a)[(size_t)(b)/(8*sizeof *(a))] op (size_t)1<<((size_t)(b)%(8*sizeof *(a))))
int dn_expand(unsigned char *b, unsigned char *pz, unsigned char *p, unsigned char *s, int outlen)
{
/* Remember jump destinations to detect loops and abort */
size_t seen[512/8/sizeof(size_t)] = { 0 };
unsigned char *sz = s + outlen;
if (pz-b > 512) return -1;
for (;;) {
if (p>=pz) return -1;
else if (*p&0xc0) {
int j = (p[0]&1) | p[1];
if (BITOP(seen, j, &)) return -1;
BITOP(seen, j, |=);
p = b + j;
} else if (*p) {
if (p+*p+1>=pz || s+*p>=sz) return -1;
memcpy(s, p+1, *p);
s += *p+1;
p += *p+1;
s[-1] = *p ? '.' : 0;
} else return 0;
}
}
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