introduce byteswap.h with osmo_{htonl,ntohl,htons,ntohs}

We need to have an architecture-independend way of endian conversion /
byte swapping functions which will also work on embedded (bare iron)
builds.   Let's introduce osmocom/core/bytesawp.h for this purpose.

Change-Id: Ibc0cc1e36d4ed63a35cf8ceff3af0f26e5ac7a3d
diff --git a/tests/Makefile.am b/tests/Makefile.am
index d9816ef..d95083b 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -16,7 +16,7 @@
 		 tlv/tlv_test gsup/gsup_test oap/oap_test fsm/fsm_test	\
 		 write_queue/wqueue_test socket/socket_test		\
 		 coding/coding_test conv/conv_gsm0503_test		\
-		 abis/abis_test
+		 abis/abis_test endian/endian_test
 
 if ENABLE_MSGFILE
 check_PROGRAMS += msgfile/msgfile_test
@@ -162,6 +162,9 @@
   $(top_builddir)/src/codec/libosmocodec.la \
   $(top_builddir)/src/coding/libosmocoding.la
 
+endian_endian_test_SOURCES = endian/endian_test.c
+endian_endian_test_LDADD = $(top_builddir)/src/libosmocore.la
+
 # The `:;' works around a Bash 3.2 bug when the output is not writeable.
 $(srcdir)/package.m4: $(top_srcdir)/configure.ac
 	:;{ \
@@ -204,7 +207,7 @@
 	     osmo-auc-gen/osmo-auc-gen_test.sh				\
 	     osmo-auc-gen/osmo-auc-gen_test.ok				\
 	     osmo-auc-gen/osmo-auc-gen_test.err				\
-	     conv/conv_gsm0503_test.ok
+	     conv/conv_gsm0503_test.ok endian/endian_test.ok
 
 DISTCLEANFILES = atconfig atlocal conv/gsm0503_test_vectors.c
 BUILT_SOURCES = conv/gsm0503_test_vectors.c
diff --git a/tests/endian/endian_test.c b/tests/endian/endian_test.c
new file mode 100644
index 0000000..8737e7a
--- /dev/null
+++ b/tests/endian/endian_test.c
@@ -0,0 +1,31 @@
+#include <osmocom/core/byteswap.h>
+#include <osmocom/core/utils.h>
+
+int main(int argc, char **argv)
+{
+	printf("Testing 16bit swappinng\n");
+	OSMO_ASSERT(osmo_swab16(0x1234) == 0x3412);
+	printf("Testing 32bit swappinng\n");
+	OSMO_ASSERT(osmo_swab32(0x12345678) == 0x78563412);
+
+	printf("Testing ntohX() and htonX()\n");
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#if OSMO_IS_LITTLE_ENDIAN == 0
+#error "Something wrong with endianness detection!"
+#endif /* IS_LITTLE_ENDIAN */
+	OSMO_ASSERT(osmo_ntohs(0x1234) == 0x3412);
+	OSMO_ASSERT(osmo_htons(0x1234) == 0x3412);
+	OSMO_ASSERT(osmo_htonl(0x12345678) == 0x78563412);
+	OSMO_ASSERT(osmo_ntohl(0x12345678) == 0x78563412);
+#else
+#if OSMO_IS_LITTLE_ENDIAN == 1
+#error "Something wrong with endianness detection!"
+#endif /* IS_LITTLE_ENDIAN */
+	OSMO_ASSERT(osmo_ntohs(0x1234) == 0x1234);
+	OSMO_ASSERT(osmo_htons(0x1234) == 0x1234);
+	OSMO_ASSERT(osmo_htonl(0x12345678) == 0x12345678);
+	OSMO_ASSERT(osmo_ntohl(0x12345678) == 0x12345678);
+#endif /* __BYTE_ORDER__ */
+
+	exit(0);
+}
diff --git a/tests/endian/endian_test.ok b/tests/endian/endian_test.ok
new file mode 100644
index 0000000..a42f457
--- /dev/null
+++ b/tests/endian/endian_test.ok
@@ -0,0 +1,3 @@
+Testing 16bit swappinng
+Testing 32bit swappinng
+Testing ntohX() and htonX()
diff --git a/tests/testsuite.at b/tests/testsuite.at
index 2f9cfe7..4c8950c 100644
--- a/tests/testsuite.at
+++ b/tests/testsuite.at
@@ -268,3 +268,9 @@
 cat $abs_srcdir/osmo-auc-gen/osmo-auc-gen_test.err > experr
 AT_CHECK([$abs_top_srcdir/tests/osmo-auc-gen/osmo-auc-gen_test.sh $abs_top_builddir/utils/osmo-auc-gen], [0], [expout], [experr])
 AT_CLEANUP
+
+AT_SETUP([endian])
+AT_KEYWORDS([endian])
+cat $abs_srcdir/endian/endian_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/endian/endian_test], [0], [expout], [ignore])
+AT_CLEANUP