if (!c || !c->parent) return EXIF_IFD_COUNT;
return
+ ((c)->parent->ifd[EXIF_IFD_EXIF] == (c)) ? EXIF_IFD_EXIF :
((c)->parent->ifd[EXIF_IFD_0] == (c)) ? EXIF_IFD_0 :
((c)->parent->ifd[EXIF_IFD_1] == (c)) ? EXIF_IFD_1 :
- ((c)->parent->ifd[EXIF_IFD_EXIF] == (c)) ? EXIF_IFD_EXIF :
((c)->parent->ifd[EXIF_IFD_GPS] == (c)) ? EXIF_IFD_GPS :
((c)->parent->ifd[EXIF_IFD_INTEROPERABILITY] == (c)) ? EXIF_IFD_INTEROPERABILITY :
EXIF_IFD_COUNT;