StdLib/LibC/Main/bswap64.c

   1 /*  $NetBSD: bswap64.c,v 1.1 2005/12/20 19:28:51 christos 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 1.1 2005/12/20 19:28:51 christos 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
  19 bswap64(UINT64 x)
  20 {
  21 #ifndef _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   u_int32_t tl, th;
  39
  40   th = bswap32((u_int32_t)(x & 0x00000000ffffffffULL));
  41   tl = bswap32((u_int32_t)((x >> 32) & 0x00000000ffffffffULL));
  42   return ((u_int64_t)th << 32) | tl;
  43 #endif
  44 }