bswap64.c revision 1.2 
1/*  $NetBSD: bswap64.c,v 1.2 2008/02/16 17:37:13 apb 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 1.2 2008/02/16 17:37:13 apb Exp $");
11#endif /* LIBC_SCCS and not lint */
12
13#include <sys/types.h>
14#include <machine/bswap.h>
15
16#undef bswap64
17
18uint64_t
19bswap64(x)
20	uint64_t x;
21{
22#ifdef _LP64
23	/*
24	 * Assume we have wide enough registers to do it without touching
25	 * memory.
26	 */
27	return  ( (x << 56) & 0xff00000000000000UL ) |
28		( (x << 40) & 0x00ff000000000000UL ) |
29		( (x << 24) & 0x0000ff0000000000UL ) |
30		( (x <<  8) & 0x000000ff00000000UL ) |
31		( (x >>  8) & 0x00000000ff000000UL ) |
32		( (x >> 24) & 0x0000000000ff0000UL ) |
33		( (x >> 40) & 0x000000000000ff00UL ) |
34		( (x >> 56) & 0x00000000000000ffUL );
35#else
36	/*
37	 * Split the operation in two 32bit steps.
38	 */
39	uint32_t tl, th;
40
41	th = bswap32((uint32_t)(x & 0x00000000ffffffffULL));
42	tl = bswap32((uint32_t)((x >> 32) & 0x00000000ffffffffULL));
43	return ((uint64_t)th << 32) | tl;
44#endif
45}
46