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

1 files changed, 43 insertions, 0 deletions

diff --git a/include/osmocom/core/byteswap.h b/include/osmocom/core/byteswap.h
new file mode 100644
index 00000000..1f09c2b1
--- /dev/null
+++ b/include/osmocom/core/byteswap.h
@@ -0,0 +1,43 @@
+#pragma once
+#include <stdint.h>
+#include <osmocom/core/endian.h>
+
+/*! \brief byte-swap a 32bit word
+ *  \param[in] in to be swapped 32bit word
+ *  \returns byte-swapped 32bit word */
+static inline uint32_t osmo_swab32(uint32_t in)
+{
+	uint32_t out;
+
+	out = (in & 0xff) << 24;
+	out |= (in & 0xff00) << 8;
+	out |= (in & 0xff0000) >> 8;
+	out |= (in & 0xff000000) >> 24;
+
+	return out;
+}
+
+/*! \brief byte-swap a 16bit word
+ *  \param[in] in to be swapped 16bit word
+ *  \returns byte-swapped 16bit word */
+static inline uint16_t osmo_swab16(uint16_t in)
+{
+	uint16_t out;
+
+	out = (in & 0xff) << 8;
+	out |= (in & 0xff00) >> 8;
+
+	return out;
+}
+
+#ifdef OSMO_IS_LITTLE_ENDIAN
+#define osmo_ntohl(x)	osmo_swab32(x)
+#define osmo_ntohs(x)	osmo_swab16(x)
+#define osmo_htonl(x)	osmo_swab32(x)
+#define osmo_htons(x)	osmo_swab16(x)
+#else
+#define osmo_ntohl(x)	(x)
+#define osmo_ntohs(x)	(x)
+#define osmo_htonl(x)	(x)
+#define osmo_htons(x)	(x)
+#endif