fusl/src/network/dn_expand.c

#include <resolv.h>
#include "libc.h"

int __dn_expand(const unsigned char* base,
                const unsigned char* end,
                const unsigned char* src,
                char* dest,
                int space) {
  const unsigned char* p = src;
  char *dend, *dbegin = dest;
  int len = -1, i, j;
  if (p == end || space <= 0)
    return -1;
  dend = dest + (space > 254 ? 254 : space);
  /* detect reference loop using an iteration counter */
  for (i = 0; i < end - base; i += 2) {
    /* loop invariants: p<end, dest<dend */
    if (*p & 0xc0) {
      if (p + 1 == end)
        return -1;
      j = ((p[0] & 0x3f) << 8) | p[1];
      if (len < 0)
        len = p + 2 - src;
      if (j >= end - base)
        return -1;
      p = base + j;
    } else if (*p) {
      if (dest != dbegin)
        *dest++ = '.';
      j = *p++;
      if (j >= end - p || j >= dend - dest)
        return -1;
      while (j--)
        *dest++ = *p++;
    } else {
      *dest = 0;
      if (len < 0)
        len = p + 1 - src;
      return len;
    }
  }
  return -1;
}

weak_alias(__dn_expand, dn_expand);