This provides the endian conversion functions form endian.h on Windows, Linux, *BSD, Mac OS X, and QNX. You still need to use -std=gnu99 instead of -std=c99 for gcc. The functions might actually be macros. Functions: htobe16, htole16, be16toh, le16toh, htobe32, htole32, be32toh, le32toh, htobe64, htole64, be64toh, le64toh. License: I hereby put …

portable_endian.h

// "License": Public Domain
// I, Mathias Panzenböck, place this file hereby into the public domain. Use it at your own risk for whatever you like.
// In case there are jurisdictions that don't support putting things in the public domain you can also consider it to
// be "dual licensed" under the BSD, MIT and Apache licenses, if you want to. This code is trivial anyway. Consider it
// an example on how to get the endian conversion functions on different platforms.

#ifndef PORTABLE_ENDIAN_H__
#define PORTABLE_ENDIAN_H__

#if (defined(_WIN16) || defined(_WIN32) || defined(_WIN64)) && !defined(__WINDOWS__)

#	define __WINDOWS__

#endif

#if defined(__linux__) || defined(__CYGWIN__)

#	include <endian.h>

#elif defined(__APPLE__)

#	include <libkern/OSByteOrder.h>

#	define htobe16(x) OSSwapHostToBigInt16(x)
#	define htole16(x) OSSwapHostToLittleInt16(x)
#	define be16toh(x) OSSwapBigToHostInt16(x)
#	define le16toh(x) OSSwapLittleToHostInt16(x)
 
#	define htobe32(x) OSSwapHostToBigInt32(x)
#	define htole32(x) OSSwapHostToLittleInt32(x)
#	define be32toh(x) OSSwapBigToHostInt32(x)
#	define le32toh(x) OSSwapLittleToHostInt32(x)
 
#	define htobe64(x) OSSwapHostToBigInt64(x)
#	define htole64(x) OSSwapHostToLittleInt64(x)
#	define be64toh(x) OSSwapBigToHostInt64(x)
#	define le64toh(x) OSSwapLittleToHostInt64(x)

#	define __BYTE_ORDER    BYTE_ORDER
#	define __BIG_ENDIAN    BIG_ENDIAN
#	define __LITTLE_ENDIAN LITTLE_ENDIAN
#	define __PDP_ENDIAN    PDP_ENDIAN

#elif defined(__OpenBSD__)

#	include <endian.h>

#	define __BYTE_ORDER    BYTE_ORDER
#	define __BIG_ENDIAN    BIG_ENDIAN
#	define __LITTLE_ENDIAN LITTLE_ENDIAN
#	define __PDP_ENDIAN    PDP_ENDIAN

#elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)

#	include <sys/endian.h>

#	define be16toh(x) betoh16(x)
#	define le16toh(x) letoh16(x)

#	define be32toh(x) betoh32(x)
#	define le32toh(x) letoh32(x)

#	define be64toh(x) betoh64(x)
#	define le64toh(x) letoh64(x)

#elif defined(__WINDOWS__)

#	include <winsock2.h>
#	ifdef __GNUC__
#		include <sys/param.h>
#	endif

#	if BYTE_ORDER == LITTLE_ENDIAN

#		define htobe16(x) htons(x)
#		define htole16(x) (x)
#		define be16toh(x) ntohs(x)
#		define le16toh(x) (x)
 
#		define htobe32(x) htonl(x)
#		define htole32(x) (x)
#		define be32toh(x) ntohl(x)
#		define le32toh(x) (x)
 
#		define htobe64(x) htonll(x)
#		define htole64(x) (x)
#		define be64toh(x) ntohll(x)
#		define le64toh(x) (x)

#	elif BYTE_ORDER == BIG_ENDIAN

		/* that would be xbox 360 */
#		define htobe16(x) (x)
#		define htole16(x) __builtin_bswap16(x)
#		define be16toh(x) (x)
#		define le16toh(x) __builtin_bswap16(x)
 
#		define htobe32(x) (x)
#		define htole32(x) __builtin_bswap32(x)
#		define be32toh(x) (x)
#		define le32toh(x) __builtin_bswap32(x)
 
#		define htobe64(x) (x)
#		define htole64(x) __builtin_bswap64(x)
#		define be64toh(x) (x)
#		define le64toh(x) __builtin_bswap64(x)

#	else

#		error byte order not supported

#	endif

#	define __BYTE_ORDER    BYTE_ORDER
#	define __BIG_ENDIAN    BIG_ENDIAN
#	define __LITTLE_ENDIAN LITTLE_ENDIAN
#	define __PDP_ENDIAN    PDP_ENDIAN

#elif defined(__QNXNTO__)

#	include <gulliver.h>

#	define __LITTLE_ENDIAN 1234
#	define __BIG_ENDIAN    4321
#	define __PDP_ENDIAN    3412

#	if defined(__BIGENDIAN__)

#		define __BYTE_ORDER __BIG_ENDIAN

#		define htobe16(x) (x)
#		define htobe32(x) (x)
#		define htobe64(x) (x)

#		define htole16(x) ENDIAN_SWAP16(x)
#		define htole32(x) ENDIAN_SWAP32(x)
#		define htole64(x) ENDIAN_SWAP64(x)

#	elif defined(__LITTLEENDIAN__)

#		define __BYTE_ORDER __LITTLE_ENDIAN

#		define htole16(x) (x)
#		define htole32(x) (x)
#		define htole64(x) (x)

#		define htobe16(x) ENDIAN_SWAP16(x)
#		define htobe32(x) ENDIAN_SWAP32(x)
#		define htobe64(x) ENDIAN_SWAP64(x)

#	else

#		error byte order not supported

#	endif

#	define be16toh(x) ENDIAN_BE16(x)
#	define be32toh(x) ENDIAN_BE32(x)
#	define be64toh(x) ENDIAN_BE64(x)
#	define le16toh(x) ENDIAN_LE16(x)
#	define le32toh(x) ENDIAN_LE32(x)
#	define le64toh(x) ENDIAN_LE64(x)

#else

#	error platform not supported

#endif

#endif

According to this SO post and comments here, ntohl doesn't inline on Windows. It's a DLL call instead of a single asm instruction...

Since there's already an #ifdef branch explicitly for LITTLE_ENDIAN Windows, I'd suggest changing avoiding ntohl there.

Pkmx's fork of this gist has that change, using _byteswap_ulong(x) instead of ntohl for MSVC, and __builtin_bswap32(x) for GNU C (gcc, clang, icc).

@blizzard4591 ,How to solve the problem of lacking of "sys/param.h" which does not exis on Windows you? I would appreciate it if you can give me some guides

@zhengqianman did you resolve sys/param.h issue for windows visual studio? If you did, could you give me some tips on resolve it?

Newlib toolchain users (other than Cygwin), you might want to have a look here:

https://gist.github.com/sjlongland/10642bf86d60bf3d9af04cf504f569da/revisions#diff-a5346b4ffac3d9b1da20a7d99957566f

Hi,

the following change adds support for GNU Hurd, and may fix build failures in case portable_endian.h is used in software packaged for Debian, as Hurd is one of the official Debian build targets.

diff --git a/portable_endian.h b/portable_endian.h
index 99845d0..1f9f490 100644
--- a/portable_endian.h
+++ b/portable_endian.h
@@ -13,7 +13,7 @@

 #endif

-#if defined(__linux__) || defined(__CYGWIN__)
+#if defined(__linux__) || defined(__CYGWIN__) || defined(__GNU__)

 #      include <endian.h>

Ciao,
Antonio

The OpenBSD code should look like this:

#elif defined(__OpenBSD__)

#        include <endian.h>

#        define __BYTE_ORDER    BYTE_ORDER
#        define __BIG_ENDIAN    BIG_ENDIAN
#        define __LITTLE_ENDIAN LITTLE_ENDIAN
#        define __POP_ENDIAN    POP_ENDIAN

Instead of this:

#elif defined(__OpenBSD__)

#	include <sys/endian.h>

#elif defined(__WINDOWS__)

#	include <winsock2.h>
#	include <sys/param.h>

"sys/param.h is a unix/linux header-file, and you shouldn't expect to find that in your Windows system." (unless you are using a GNU compiler.)
https://stackoverflow.com/questions/18333651/vs2010-can-not-open-include-file-sys-param-h

to me it looks like this patch from 2014 adressed it already on the source tree of someone else:
PDAL/PDAL@c432437

(no idea who invented this first and who branched that "idea" from whom - at least the upstream connection seemingly is broken nowadays)

thinking again - your code might work perfectly for GNU C on the windows platform.
guess what - people are trying out to compile it with MSVC - and its just not documented that you were not targeting that compiler.

Defining __WINDOWS__ is not good. #ifdef __WINDOWS__ can work differently in files that include and don't include endian.h, which would be surprising. It's better to define symbols that communicate their limited scope, e.g. __ENDIAN_WINDOWS.
The use of __builtin_bswapNN whould be limited to the compiles that define it (GCC and Clang, both define __GNUC__).

This header is useful. I want to create a conan package. Counld you please create a repo for this gist to support a better version control?

I haven't updated this in 6 years, I think it's save to say there won't be any new version of this. I'm not maintaining it. 😄
Just copy the file/code wherever you need it. I really don't see the benefit of a full repo for that. All that would do is people writing issues that I don't feel like fixing. A gist makes clear its just an example on how one can do something like this.

There is currently no support for QNX Neutrino. You can add it easily as shown below:

#elif defined(__QNXNTO__)

#	include <gulliver.h>