unsigned CLASS pana_bits (int nbits)
{
  static uchar buf[0x4000];
  static int vbits;
  int byte;

  if (!nbits) return vbits=0;
  if (!vbits) {
    fread (buf+load_flags, 1, 0x4000-load_flags, ifp);
    fread (buf, 1, load_flags, ifp);
  }
  vbits = (vbits - nbits) & 0x1ffff;
  byte = vbits >> 3 ^ 0x3ff0;
  return (buf[byte] | buf[byte+1] << 8) >> (vbits & 7) & ~(-1 << nbits);
}

This weakness involves numeric computation errors, such as integer overflows, underflows, or precision losses, which can lead to miscalculations and exploitable behaviors in software.