common/lib/libc/gen/bswap64.c

   1 /*  $NetBSD: bswap64.c,v 1.3 2009/03/16 05:59:21 cegger Exp $    */
   2
   3 /*
   4  * Written by Manuel Bouyer <bouyer@NetBSD.org>.
   5  * Public domain.
   6  */
   7
   8 #include <sys/cdefs.h>
   9 #if defined(LIBC_SCCS) && !defined(lint)
  10 __RCSID("$NetBSD: bswap64.c,v 1.3 2009/03/16 05:59:21 cegger Exp $");
  11 #endif /* LIBC_SCCS and not lint */
  12
  13 #include <sys/types.h>
  14 #include <machine/bswap.h>
  15
  16 #undef bswap64
  17
  18 uint64_t
  19 bswap64(uint64_t x)
  20 {
  21 #ifdef _LP64
  22         /*
  23          * Assume we have wide enough registers to do it without touching
  24          * memory.
  25          */
  26         return  ( (x << 56) & 0xff00000000000000UL ) |
  27                 ( (x << 40) & 0x00ff000000000000UL ) |
  28                 ( (x << 24) & 0x0000ff0000000000UL ) |
  29                 ( (x <<  8) & 0x000000ff00000000UL ) |
  30                 ( (x >>  8) & 0x00000000ff000000UL ) |
  31                 ( (x >> 24) & 0x0000000000ff0000UL ) |
  32                 ( (x >> 40) & 0x000000000000ff00UL ) |
  33                 ( (x >> 56) & 0x00000000000000ffUL );
  34 #else
  35         /*
  36          * Split the operation in two 32bit steps.
  37          */
  38         uint32_t tl, th;
  39
  40         th = bswap32((uint32_t)(x & 0x00000000ffffffffULL));
  41         tl = bswap32((uint32_t)((x >> 32) & 0x00000000ffffffffULL));
  42         return ((uint64_t)th << 32) | tl;
  43 #endif
  44 }