m4/endian.m4

dnl Copyright (C) 2012  Xiph.org Foundation
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dnl @synopsis XIPH_C_FIND_ENDIAN
dnl
dnl Determine endian-ness of target processor.
dnl @version 1.1	Mar 03 2002
dnl @author Erik de Castro Lopo <erikd@mega-nerd.com>
dnl
dnl Majority written from scratch to replace the standard autoconf macro
dnl AC_C_BIGENDIAN. Only part remaining from the original is the invocation
dnl of the AC_TRY_RUN macro.
dnl
dnl Find endian-ness in the following way:
dnl    1) Look in <endian.h>.
dnl    2) If 1) fails, look in <sys/types.h> and <sys/param.h>.
dnl    3) If 1) and 2) fails and not cross compiling run a test program.
dnl    4) If 1) and 2) fails and cross compiling then guess based on target.

AC_DEFUN([XIPH_C_FIND_ENDIAN],
[AC_CACHE_CHECK(processor byte ordering,
	ac_cv_c_byte_order,

# Initialize to unknown
ac_cv_c_byte_order=unknown

if test x$ac_cv_header_endian_h = xyes ; then

	# First try <endian.h> which should set BYTE_ORDER.

	[AC_TRY_LINK([
		#include <endian.h>
		#if BYTE_ORDER != LITTLE_ENDIAN
			not big endian
		#endif
		], return 0 ;,
			ac_cv_c_byte_order=little
		)]

	[AC_TRY_LINK([
		#include <endian.h>
		#if BYTE_ORDER != BIG_ENDIAN
			not big endian
		#endif
		], return 0 ;,
			ac_cv_c_byte_order=big
		)]

	fi

if test $ac_cv_c_byte_order = unknown ; then

	[AC_TRY_LINK([
		#include <sys/types.h>
		#include <sys/param.h>
		#if !BYTE_ORDER || !BIG_ENDIAN || !LITTLE_ENDIAN
			bogus endian macros
		#endif
		], return 0 ;,

		[AC_TRY_LINK([
			#include <sys/types.h>
			#include <sys/param.h>
			#if BYTE_ORDER != LITTLE_ENDIAN
				not big endian
			#endif
			], return 0 ;,
				ac_cv_c_byte_order=little
			)]

		[AC_TRY_LINK([
			#include <sys/types.h>
			#include <sys/param.h>
			#if BYTE_ORDER != LITTLE_ENDIAN
				not big endian
			#endif
			], return 0 ;,
				ac_cv_c_byte_order=little
			)]

		)]

 	fi

if test $ac_cv_c_byte_order = unknown ; then
	if test $cross_compiling = yes ; then
		# This is the last resort. Try to guess the target processor endian-ness
		# by looking at the target CPU type.
		[
		case "$target_cpu" in
			alpha* | i?86* | mipsel* | ia64*)
				ac_cv_c_byte_order=little
				;;

			m68* | mips* | powerpc* | hppa* | sparc*)
				ac_cv_c_byte_order=big
				;;

			esac
		]
	else
		AC_TRY_RUN(
		[[
		int main (void)
		{	/* Are we little or big endian?  From Harbison&Steele.  */
			union
			{	long l ;
				char c [sizeof (long)] ;
			} u ;
			u.l = 1 ;
			return (u.c [sizeof (long) - 1] == 1);
			}
			]], , ac_cv_c_byte_order=big,
			)

		AC_TRY_RUN(
		[[int main (void)
		{	/* Are we little or big endian?  From Harbison&Steele.  */
			union
			{	long l ;
				char c [sizeof (long)] ;
			} u ;
			u.l = 1 ;
			return (u.c [0] == 1);
			}]], , ac_cv_c_byte_order=little,
			)
		fi
	fi

)

if test $ac_cv_c_byte_order = big ; then
	ac_cv_c_big_endian=1
	ac_cv_c_little_endian=0
elif test $ac_cv_c_byte_order = little ; then
	ac_cv_c_big_endian=0
	ac_cv_c_little_endian=1
else
	ac_cv_c_big_endian=0
	ac_cv_c_little_endian=0

	AC_MSG_WARN([[*****************************************************************]])
	AC_MSG_WARN([[*** Not able to determine endian-ness of target processor.       ]])
	AC_MSG_WARN([[*** The constants CPU_IS_BIG_ENDIAN and CPU_IS_LITTLE_ENDIAN in  ]])
	AC_MSG_WARN([[*** config.h may need to be hand editied.                        ]])
	AC_MSG_WARN([[*****************************************************************]])
	fi

]
)# XIPH_C_FIND_ENDIAN