--- /dev/null
+#ifndef _LWK_BYTEORDER_SWAB_H
+#define _LWK_BYTEORDER_SWAB_H
+
+/*
+ * lwk/byteorder/swab.h
+ * Byte-swapping, independently from CPU endianness
+ * swabXX[ps]?(foo)
+ *
+ * Francois-Rene Rideau <fare@tunes.org> 19971205
+ * separated swab functions from cpu_to_XX,
+ * to clean up support for bizarre-endian architectures.
+ *
+ * See asm-i386/byteorder.h and suches for examples of how to provide
+ * architecture-dependent optimized versions
+ *
+ */
+
+#include <lwk/compiler.h>
+
+/* casts are necessary for constants, because we never know how for sure
+ * how U/UL/ULL map to __u16, __u32, __u64. At least not in a portable way.
+ */
+#define ___swab16(x) \
+({ \
+ __u16 __x = (x); \
+ ((__u16)( \
+ (((__u16)(__x) & (__u16)0x00ffU) << 8) | \
+ (((__u16)(__x) & (__u16)0xff00U) >> 8) )); \
+})
+
+#define ___swab32(x) \
+({ \
+ __u32 __x = (x); \
+ ((__u32)( \
+ (((__u32)(__x) & (__u32)0x000000ffUL) << 24) | \
+ (((__u32)(__x) & (__u32)0x0000ff00UL) << 8) | \
+ (((__u32)(__x) & (__u32)0x00ff0000UL) >> 8) | \
+ (((__u32)(__x) & (__u32)0xff000000UL) >> 24) )); \
+})
+
+#define ___swab64(x) \
+({ \
+ __u64 __x = (x); \
+ ((__u64)( \
+ (__u64)(((__u64)(__x) & (__u64)0x00000000000000ffULL) << 56) | \
+ (__u64)(((__u64)(__x) & (__u64)0x000000000000ff00ULL) << 40) | \
+ (__u64)(((__u64)(__x) & (__u64)0x0000000000ff0000ULL) << 24) | \
+ (__u64)(((__u64)(__x) & (__u64)0x00000000ff000000ULL) << 8) | \
+ (__u64)(((__u64)(__x) & (__u64)0x000000ff00000000ULL) >> 8) | \
+ (__u64)(((__u64)(__x) & (__u64)0x0000ff0000000000ULL) >> 24) | \
+ (__u64)(((__u64)(__x) & (__u64)0x00ff000000000000ULL) >> 40) | \
+ (__u64)(((__u64)(__x) & (__u64)0xff00000000000000ULL) >> 56) )); \
+})
+
+#define ___constant_swab16(x) \
+ ((__u16)( \
+ (((__u16)(x) & (__u16)0x00ffU) << 8) | \
+ (((__u16)(x) & (__u16)0xff00U) >> 8) ))
+#define ___constant_swab32(x) \
+ ((__u32)( \
+ (((__u32)(x) & (__u32)0x000000ffUL) << 24) | \
+ (((__u32)(x) & (__u32)0x0000ff00UL) << 8) | \
+ (((__u32)(x) & (__u32)0x00ff0000UL) >> 8) | \
+ (((__u32)(x) & (__u32)0xff000000UL) >> 24) ))
+#define ___constant_swab64(x) \
+ ((__u64)( \
+ (__u64)(((__u64)(x) & (__u64)0x00000000000000ffULL) << 56) | \
+ (__u64)(((__u64)(x) & (__u64)0x000000000000ff00ULL) << 40) | \
+ (__u64)(((__u64)(x) & (__u64)0x0000000000ff0000ULL) << 24) | \
+ (__u64)(((__u64)(x) & (__u64)0x00000000ff000000ULL) << 8) | \
+ (__u64)(((__u64)(x) & (__u64)0x000000ff00000000ULL) >> 8) | \
+ (__u64)(((__u64)(x) & (__u64)0x0000ff0000000000ULL) >> 24) | \
+ (__u64)(((__u64)(x) & (__u64)0x00ff000000000000ULL) >> 40) | \
+ (__u64)(((__u64)(x) & (__u64)0xff00000000000000ULL) >> 56) ))
+
+/*
+ * provide defaults when no architecture-specific optimization is detected
+ */
+#ifndef __arch__swab16
+# define __arch__swab16(x) ({ __u16 __tmp = (x) ; ___swab16(__tmp); })
+#endif
+#ifndef __arch__swab32
+# define __arch__swab32(x) ({ __u32 __tmp = (x) ; ___swab32(__tmp); })
+#endif
+#ifndef __arch__swab64
+# define __arch__swab64(x) ({ __u64 __tmp = (x) ; ___swab64(__tmp); })
+#endif
+
+#ifndef __arch__swab16p
+# define __arch__swab16p(x) __arch__swab16(*(x))
+#endif
+#ifndef __arch__swab32p
+# define __arch__swab32p(x) __arch__swab32(*(x))
+#endif
+#ifndef __arch__swab64p
+# define __arch__swab64p(x) __arch__swab64(*(x))
+#endif
+
+#ifndef __arch__swab16s
+# define __arch__swab16s(x) do { *(x) = __arch__swab16p((x)); } while (0)
+#endif
+#ifndef __arch__swab32s
+# define __arch__swab32s(x) do { *(x) = __arch__swab32p((x)); } while (0)
+#endif
+#ifndef __arch__swab64s
+# define __arch__swab64s(x) do { *(x) = __arch__swab64p((x)); } while (0)
+#endif
+
+
+/*
+ * Allow constant folding
+ */
+#if defined(__GNUC__) && defined(__OPTIMIZE__)
+# define __swab16(x) \
+(__builtin_constant_p((__u16)(x)) ? \
+ ___swab16((x)) : \
+ __fswab16((x)))
+# define __swab32(x) \
+(__builtin_constant_p((__u32)(x)) ? \
+ ___swab32((x)) : \
+ __fswab32((x)))
+# define __swab64(x) \
+(__builtin_constant_p((__u64)(x)) ? \
+ ___swab64((x)) : \
+ __fswab64((x)))
+#else
+# define __swab16(x) __fswab16(x)
+# define __swab32(x) __fswab32(x)
+# define __swab64(x) __fswab64(x)
+#endif /* OPTIMIZE */
+
+
+static __inline__ __attribute_const__ __u16 __fswab16(__u16 x)
+{
+ return __arch__swab16(x);
+}
+static __inline__ __u16 __swab16p(const __u16 *x)
+{
+ return __arch__swab16p(x);
+}
+static __inline__ void __swab16s(__u16 *addr)
+{
+ __arch__swab16s(addr);
+}
+
+static __inline__ __attribute_const__ __u32 __fswab32(__u32 x)
+{
+ return __arch__swab32(x);
+}
+static __inline__ __u32 __swab32p(const __u32 *x)
+{
+ return __arch__swab32p(x);
+}
+static __inline__ void __swab32s(__u32 *addr)
+{
+ __arch__swab32s(addr);
+}
+
+#ifdef __BYTEORDER_HAS_U64__
+static __inline__ __attribute_const__ __u64 __fswab64(__u64 x)
+{
+# ifdef __SWAB_64_THRU_32__
+ __u32 h = x >> 32;
+ __u32 l = x & ((1ULL<<32)-1);
+ return (((__u64)__swab32(l)) << 32) | ((__u64)(__swab32(h)));
+# else
+ return __arch__swab64(x);
+# endif
+}
+static __inline__ __u64 __swab64p(const __u64 *x)
+{
+ return __arch__swab64p(x);
+}
+static __inline__ void __swab64s(__u64 *addr)
+{
+ __arch__swab64s(addr);
+}
+#endif /* __BYTEORDER_HAS_U64__ */
+
+#if defined(__KERNEL__)
+#define swab16 __swab16
+#define swab32 __swab32
+#define swab64 __swab64
+#define swab16p __swab16p
+#define swab32p __swab32p
+#define swab64p __swab64p
+#define swab16s __swab16s
+#define swab32s __swab32s
+#define swab64s __swab64s
+#endif
+
+#endif /* _LWK_BYTEORDER_SWAB_H */
