Source: inc_sdif.h

#if defined (__GNUC__)  &&  defined (__alpha__)
/* swap multibyte char constant s with gcc on alpha (see
   src/specenv/library/estimation/estimation.h) */
#   define isolate(s, n)    ((s) & (0xff << ((n) * 8)))   /* s is char const */
#   define shiftto0(s, n)   (s >> ((n) * 8))
#   define pick(s, n)       (shiftto0 (isolate (s, n), n) << ((3 - (n)) * 8))
#   define Signature(s)     (pick(s, 0) | pick(s, 1) | pick(s, 2) | pick(s, 3))
#else            
#   define Signature(s)     s
#endif            
 
#include <sdif/sdif.h>