m4/tuklib_integer.m4

#
# SYNOPSIS
#
#   TUKLIB_INTEGER
#
# DESCRIPTION
#
#   Checks for tuklib_integer.h:
#     - Endianness
#     - Does operating system provide byte swapping macros
#     - Does the hardware support fast unaligned access to 16-bit
#       and 32-bit integers
#
# COPYING
#
#   Author: Lasse Collin
#
#   This file has been put into the public domain.
#   You can do whatever you want with this file.
#

AC_DEFUN_ONCE([TUKLIB_INTEGER], [
AC_REQUIRE([TUKLIB_COMMON])
AC_REQUIRE([AC_C_BIGENDIAN])
AC_CHECK_HEADERS([byteswap.h sys/endian.h sys/byteorder.h], [break])

# Even if we have byteswap.h, we may lack the specific macros/functions.
if test x$ac_cv_header_byteswap_h = xyes ; then
	m4_foreach([FUNC], [bswap_16,bswap_32,bswap_64], [
		AC_MSG_CHECKING([if FUNC is available])
		AC_LINK_IFELSE([AC_LANG_SOURCE([
#include <byteswap.h>
int
main(void)
{
	FUNC[](42);
	return 0;
}
		])], [
			AC_DEFINE(HAVE_[]m4_toupper(FUNC), [1],
					[Define to 1 if] FUNC [is available.])
			AC_MSG_RESULT([yes])
		], [AC_MSG_RESULT([no])])

	])dnl
fi

AC_MSG_CHECKING([if unaligned memory access should be used])
AC_ARG_ENABLE([unaligned-access], AS_HELP_STRING([--enable-unaligned-access],
		[Enable if the system supports *fast* unaligned memory access
		with 16-bit and 32-bit integers. By default, this is enabled
		only on x86, x86_64, and big endian PowerPC.]),
	[], [enable_unaligned_access=auto])
if test "x$enable_unaligned_access" = xauto ; then
	# TODO: There may be other architectures, on which unaligned access
	# is OK.
	case $host_cpu in
		i?86|x86_64|powerpc|powerpc64)
			enable_unaligned_access=yes
			;;
		*)
			enable_unaligned_access=no
			;;
	esac
fi
if test "x$enable_unaligned_access" = xyes ; then
	AC_DEFINE([TUKLIB_FAST_UNALIGNED_ACCESS], [1], [Define to 1 if
		the system supports fast unaligned access to 16-bit and
		32-bit integers.])
	AC_MSG_RESULT([yes])
else
	AC_MSG_RESULT([no])
fi
])dnl