--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/byteordering.h	Tue Jun 25 13:55:11 2013 +0800
@@ -0,0 +1,188 @@
+
+/*
+ * Copyright (c) 2006-2012 by Roland Riegel <[email protected]>
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either the GNU General Public License version 2
+ * or the GNU Lesser General Public License version 2.1, both as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef BYTEORDERING_H
+#define BYTEORDERING_H
+
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/**
+ * \addtogroup byteordering
+ *
+ * @{
+ */
+/**
+ * \file
+ * Byte-order handling header (license: GPLv2 or LGPLv2.1)
+ *
+ * \author Roland Riegel
+ */
+
+#define SWAP16(val) ((((uint16_t) (val)) << 8) | \
+                     (((uint16_t) (val)) >> 8)   \
+                    )
+#define SWAP32(val) (((((uint32_t) (val)) & 0x000000ff) << 24) | \
+                     ((((uint32_t) (val)) & 0x0000ff00) <<  8) | \
+                     ((((uint32_t) (val)) & 0x00ff0000) >>  8) | \
+                     ((((uint32_t) (val)) & 0xff000000) >> 24)   \
+                    )
+
+#if LITTLE_ENDIAN || __AVR__
+#define SWAP_NEEDED 0
+#elif BIG_ENDIAN
+#define SWAP_NEEDED 1
+#else
+#error "Endianess undefined! Please define LITTLE_ENDIAN=1 or BIG_ENDIAN=1."
+#endif
+
+/**
+ * \def HTOL16(val)
+ *
+ * Converts a 16-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function htol16() instead. This saves code size.
+ *
+ * \param[in] val A 16-bit integer in host byte order.
+ * \returns The given 16-bit integer converted to little-endian byte order.
+ */
+/**
+ * \def HTOL32(val)
+ *
+ * Converts a 32-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function htol32() instead. This saves code size.
+ *
+ * \param[in] val A 32-bit integer in host byte order.
+ * \returns The given 32-bit integer converted to little-endian byte order.
+ */
+/**
+ * \def LTOH16(val)
+ *
+ * Converts a 16-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function ltoh16() instead. This saves code size.
+ *
+ * \param[in] val A 16-bit integer in little-endian byte order.
+ * \returns The given 16-bit integer converted to host byte order.
+ */
+/**
+ * \def LTOH32(val)
+ *
+ * Converts a 32-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this macro for compile time constants only. For variable values
+ * use the function ltoh32() instead. This saves code size.
+ *
+ * \param[in] val A 32-bit integer in little-endian byte order.
+ * \returns The given 32-bit integer converted to host byte order.
+ */
+
+#if SWAP_NEEDED
+#define HTOL16(val) SWAP16(val)
+#define HTOL32(val) SWAP32(val)
+#define LTOH16(val) SWAP16(val)
+#define LTOH32(val) SWAP32(val)
+#else
+#define HTOL16(val) (val)
+#define HTOL32(val) (val)
+#define LTOH16(val) (val)
+#define LTOH32(val) (val)
+#endif
+
+#if DOXYGEN
+
+/**
+ * Converts a 16-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro HTOL16(). This saves code size.
+ *
+ * \param[in] h A 16-bit integer in host byte order.
+ * \returns The given 16-bit integer converted to little-endian byte order.
+ */
+uint16_t htol16(uint16_t h);
+
+/**
+ * Converts a 32-bit integer from host byte order to little-endian byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro HTOL32(). This saves code size.
+ *
+ * \param[in] h A 32-bit integer in host byte order.
+ * \returns The given 32-bit integer converted to little-endian byte order.
+ */
+uint32_t htol32(uint32_t h);
+
+/**
+ * Converts a 16-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro LTOH16(). This saves code size.
+ *
+ * \param[in] l A 16-bit integer in little-endian byte order.
+ * \returns The given 16-bit integer converted to host byte order.
+ */
+uint16_t ltoh16(uint16_t l);
+
+/**
+ * Converts a 32-bit integer from little-endian byte order to host byte order.
+ *
+ * Use this function on variable values instead of the
+ * macro LTOH32(). This saves code size.
+ *
+ * \param[in] l A 32-bit integer in little-endian byte order.
+ * \returns The given 32-bit integer converted to host byte order.
+ */
+uint32_t ltoh32(uint32_t l);
+
+#elif SWAP_NEEDED
+
+#define htol16(h) swap16(h)
+#define htol32(h) swap32(h)
+#define ltoh16(l) swap16(l)
+#define ltoh32(l) swap32(l)
+
+#else
+
+#define htol16(h) (h)
+#define htol32(h) (h)
+#define ltoh16(l) (l)
+#define ltoh32(l) (l)
+
+#endif
+
+uint16_t read16(const uint8_t* p);
+uint32_t read32(const uint8_t* p);
+void write16(uint8_t* p, uint16_t i);
+void write32(uint8_t* p, uint32_t i);
+
+/**
+ * @}
+ */
+
+#if SWAP_NEEDED
+uint16_t swap16(uint16_t i);
+uint32_t swap32(uint32_t i);
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+