libc/unistd/swab.c

   1 #include <unistd.h>
   2 #include <sys/types.h>
   3 #include <byteswap.h>
   4
   5 /* Updated implementation based on byteswap.h from Miles Bader
   6  * <miles@gnu.org>.  This should be much faster on arches with machine
   7  * specific, optimized definitions in include/bits/byteswap.h (i.e. on
   8  * x86, use the bswap instruction on i486 and better boxes).  For
   9  * platforms that lack such support, this should be no slower than it
  10  * was before... */
  11 void swab (const void *source, void *dest, ssize_t count)
  12 {
  13     const unsigned short *from = source, *from_end = from + (count >> 1);
  14     unsigned short junk;
  15     unsigned short *to = dest;
  16
  17     while (from < from_end) {
  18         /* Don't put '*from++'into the bswap_16() macros
  19          * or mad things will happen on macro expansion */
  20         junk=*from++;
  21         *to++ = bswap_16 (junk);
  22     }
  23 }