mkvtoolnix/ac/endianess.m4
2017-03-27 19:27:00 +02:00

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dnl Stolen from VideoLAN Client, http://www.videolan.org/
dnl
dnl Endianness check, AC_C_BIGENDIAN doesn't work if we are cross-compiling
dnl
dnl We give the user the opportunity to specify
dnl --with-words=big or --with-words=little ; otherwise, try to guess
dnl
AC_ARG_WITH(words,
AC_HELP_STRING([--with-words=endianness],[set endianness (big or little)]))
case "${with_words}" in
big)
ac_cv_c_bigendian=yes
;;
little)
ac_cv_c_bigendian=no
;;
*)
dnl Try to guess endianness by matching patterns on a compiled
dnl binary, by looking for an ASCII or EBCDIC string
AC_CACHE_CHECK([whether the byte order is big-endian],
[ac_cv_c_bigendian],
[ac_cv_c_bigendian="unknown"
[cat >conftest.c <<EOF
short am[] = { 0x4249, 0x4765, 0x6e44, 0x6961, 0x6e53, 0x7953, 0 };
short ai[] = { 0x694c, 0x5454, 0x656c, 0x6e45, 0x6944, 0x6e61, 0 };
void _a(void) { char*s = (char*)am; s = (char *)ai; }
short ei[] = { 0x89D3, 0xe3e3, 0x8593, 0x95c5, 0x89c4, 0x9581, 0 };
short em[] = { 0xc2c9, 0xc785, 0x95c4, 0x8981, 0x95e2, 0xa8e2, 0 };
void _e(void) { char*s = (char*)em; s = (char*)ei; }
int main(void) { _a(); _e(); return 0; }
EOF
]
if test -f conftest.c
then
if ${CC-cc} -c conftest.c -o conftest.o >>config.log 2>&1 \
&& test -f conftest.o
then
if test "`"$STRINGS" conftest.o | grep BIGenDianSyS`"
then
ac_cv_c_bigendian="yes"
fi
if test "`"$STRINGS" conftest.o | grep LiTTleEnDian`"
then
ac_cv_c_bigendian="no"
fi
fi
fi
])
if test "${ac_cv_c_bigendian}" = "unknown"
then
AC_MSG_ERROR([Could not guess endianness, please use --with-words])
fi
;;
esac
dnl Now we know what to use for endianness, just put it in the header
if test "${ac_cv_c_bigendian}" = "yes"
then
AC_DEFINE(WORDS_BIGENDIAN, 1, big endian system)
fi