byteorder.h

linux下的gcc编译器

/*  DO NOT EDIT THIS FILE.

    It has been auto-edited by fixincludes from:

	"fixinc/tests/inc/sys/byteorder.h"

    This had to be done to correct non-standard usages in the
    original, manufacturer supplied header file.  */

#ifndef _SYS_BYTEORDER_H
#define _SYS_BYTEORDER_H

/* Functions to convert `short' and `long' quantities from host byte order
   to (internet) network byte order (i.e. big-endian).

   Written by Ron Guilmette ([e-mail]).

   This isn't actually used by GCC.  It is installed by fixinc.svr4.

   For big-endian machines these functions are essentially no-ops.

   For little-endian machines, we define the functions using specialized
   asm sequences in cases where doing so yields better code (e.g. i386).  */

#if !defined (__GNUC__) && !defined (__GNUG__)
#error You lose!  This file is only useful with GNU compilers.
#endif

#ifndef __BYTE_ORDER__
/* Byte order defines.  These are as defined on UnixWare 1.1, but with
   double underscores added at the front and back.  */
#define __LITTLE_ENDIAN__   1234
#define __BIG_ENDIAN__      4321
#define __PDP_ENDIAN__      3412
#endif

#ifdef __STDC__
static __inline__ unsigned long htonl (unsigned long);
static __inline__ unsigned short htons (unsigned int);
static __inline__ unsigned long ntohl (unsigned long);
static __inline__ unsigned short ntohs (unsigned int);
#endif /* defined (__STDC__) */

#if defined (__i386__)

#ifndef __BYTE_ORDER__
#define __BYTE_ORDER__ __LITTLE_ENDIAN__
#endif

/* Convert a host long to a network long.  */

/* We must use a new-style function definition, so that this will also
   be valid for C++.  */
static __inline__ unsigned long
htonl (unsigned long __arg)
{
  register unsigned long __result;

  __asm__ ("xchg%B0 %b0,%h0 ; ror%L0 $16,%0 ; xchg%B0 %b0,%h0"     : "=q" (__result) : "0" (__arg));
  return __result;
}

/* Convert a host short to a network short.  */

static __inline__ unsigned short
htons (unsigned int __arg)
{
  register unsigned short __result;

  __asm__ ("xchg%B0 %b0,%h0" : "=q" (__result) : "0" (__arg));
  return __result;
}

#elif ((defined (__i860__) && !defined (__i860_big_endian__))	\
       || defined (__ns32k__) || defined (__vax__)		\
       || defined (__spur__) || defined (__arm__))

#ifndef __BYTE_ORDER__
#define __BYTE_ORDER__ __LITTLE_ENDIAN__
#endif

/* For other little-endian machines, using C code is just as efficient as
   using assembly code.  */

/* Convert a host long to a network long.  */

static __inline__ unsigned long
htonl (unsigned long __arg)
{
  register unsigned long __result;

  __result = (__arg >> 24) & 0x000000ff;
  __result |= (__arg >> 8) & 0x0000ff00;
  __result |= (__arg << 8) & 0x00ff0000;
  __result |= (__arg << 24) & 0xff000000;
  return __result;
}

/* Convert a host short to a network short.  */

static __inline__ unsigned short
htons (unsigned int __arg)
{
  register unsigned short __result;

  __result = (__arg << 8) & 0xff00;
  __result |= (__arg >> 8) & 0x00ff;
  return __result;
}

#else /* must be a big-endian machine */

#ifndef __BYTE_ORDER__
#define __BYTE_ORDER__ __BIG_ENDIAN__
#endif

/* Convert a host long to a network long.  */

static __inline__ unsigned long
htonl (unsigned long __arg)
{
  return __arg;
}

/* Convert a host short to a network short.  */

static __inline__ unsigned short
htons (unsigned int __arg)
{
  return __arg;
}

#endif /* big-endian */

/* Convert a network long to a host long.  */

static __inline__ unsigned long
ntohl (unsigned long __arg)
{
  return htonl (__arg);
}

/* Convert a network short to a host short.  */

static __inline__ unsigned short
ntohs (unsigned int __arg)
{
  return htons (__arg);
}
#endif