usr/src/boot/lib/libstand/bswap.c

   1 /*
   2  * Written by Manuel Bouyer <bouyer@netbsd.org>.
   3  * Public domain.
   4  */
   5
   6 #include <sys/cdefs.h>
   7 __FBSDID("$FreeBSD$");
   8
   9 #if defined(LIBC_SCCS) && !defined(lint)
  10 static char *rcsid = "$NetBSD: bswap32.c,v 1.1 1997/10/09 15:42:33 bouyer Exp $";
  11 static char *rcsid = "$NetBSD: bswap64.c,v 1.3 2009/03/16 05:59:21 cegger Exp $";
  12 #endif
  13
  14 #include <sys/types.h>
  15
  16 #undef bswap32
  17 #undef bswap64
  18
  19 u_int32_t bswap32(u_int32_t x);
  20 u_int64_t bswap64(u_int64_t x);
  21
  22 u_int32_t
  23 bswap32(u_int32_t x)
  24 {
  25         return  ((x << 24) & 0xff000000 ) |
  26                         ((x <<  8) & 0x00ff0000 ) |
  27                         ((x >>  8) & 0x0000ff00 ) |
  28                         ((x >> 24) & 0x000000ff );
  29 }
  30
  31 u_int64_t
  32 bswap64(u_int64_t x)
  33 {
  34 #ifdef __LP64__
  35         /*
  36          * Assume we have wide enough registers to do it without touching
  37          * memory.
  38          */
  39         return  ( (x << 56) & 0xff00000000000000UL ) |
  40                 ( (x << 40) & 0x00ff000000000000UL ) |
  41                 ( (x << 24) & 0x0000ff0000000000UL ) |
  42                 ( (x <<  8) & 0x000000ff00000000UL ) |
  43                 ( (x >>  8) & 0x00000000ff000000UL ) |
  44                 ( (x >> 24) & 0x0000000000ff0000UL ) |
  45                 ( (x >> 40) & 0x000000000000ff00UL ) |
  46                 ( (x >> 56) & 0x00000000000000ffUL );
  47 #else
  48         /*
  49          * Split the operation in two 32bit steps.
  50          */
  51         u_int32_t tl, th;
  52
  53         th = bswap32((u_int32_t)(x & 0x00000000ffffffffULL));
  54         tl = bswap32((u_int32_t)((x >> 32) & 0x00000000ffffffffULL));
  55         return ((u_int64_t)th << 32) | tl;
  56 #endif
  57 }