linux系统平台文件/usr/include/asm/byteorder.h

#ifndef _I386_BYTEORDER_H
#define _I386_BYTEORDER_H

#include <asm/types.h>
//#include <linux/compiler.h>

#ifdef __GNUC__

/* For avoiding bswap on i386 */
#ifdef __KERNEL__
#include <linux/config.h>
#endif

static __inline__ __u32 ___arch__swab32(__u32 x)
{
#ifdef CONFIG_X86_BSWAP
        __asm__("bswap %0" : "=r" (x) : "0" (x));
#else
        __asm__("xchgb %b0,%h0\n\t" /* swap lower bytes */
                "rorl $16,%0\n\t" /* swap words */
                "xchgb %b0,%h0" /* swap higher bytes */
                :"=q" (x)
                : "0" (x));
#endif
        return x;
}

static __inline__ __u64 ___arch__swab64(__u64 val)
{
        union {
                struct { __u32 a,b; } s;
                __u64 u;
        } v;
        v.u = val;
#ifdef CONFIG_X86_BSWAP
        asm("bswapl %0 ; bswapl %1 ; xchgl %0,%1"
            : "=r" (v.s.a), "=r" (v.s.b)
            : "0" (v.s.a), "1" (v.s.b));
#else
   v.s.a = ___arch__swab32(v.s.a);
        v.s.b = ___arch__swab32(v.s.b);
        asm("xchgl %0,%1" : "=r" (v.s.a), "=r" (v.s.b) : "0" (v.s.a), "1" (v.s.b));
#endif
        return v.u;
}

/* Do not define swab16. Gcc is smart enough to recognize "C" version and
   convert it into rotation or exhange. */

#define __arch__swab64(x) ___arch__swab64(x)
#define __arch__swab32(x) ___arch__swab32(x)

#define __BYTEORDER_HAS_U64__

#endif /* __GNUC__ */

#include <linux/byteorder/little_endian.h>

#endif /* _I386_BYTEORDER_H */