simple riddle about macro

Bellow is a macro from Perl source code (perl.h).

# define _swab_32_(x) ((U32)( \
         (((U32)(x) & U32_CONST(0x000000ff)) << 24) | \
         (((U32)(x) & U32_CONST(0x0000ff00)) <<  8) | \
         (((U32)(x) & U32_CONST(0x00ff0000)) >>  8) | \
         (((U32)(x) & U32_CONST(0xff000000)) >> 24) ))

Provide at least 3 ideas, how this may be reused in other projects.

>>35
You only notice the things that my mind filters out. Enjoy having to manually indent when my editor can do it for me.