--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _LINUX_SWAB_H
+#define _LINUX_SWAB_H
+
+#include <linux/types.h>
+
+#include <asm/bitsperlong.h>
+#include <asm/swab.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 ___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)(x) & (__u64)0x00000000000000ffULL) << 56) | \
+ (((__u64)(x) & (__u64)0x000000000000ff00ULL) << 40) | \
+ (((__u64)(x) & (__u64)0x0000000000ff0000ULL) << 24) | \
+ (((__u64)(x) & (__u64)0x00000000ff000000ULL) << 8) | \
+ (((__u64)(x) & (__u64)0x000000ff00000000ULL) >> 8) | \
+ (((__u64)(x) & (__u64)0x0000ff0000000000ULL) >> 24) | \
+ (((__u64)(x) & (__u64)0x00ff000000000000ULL) >> 40) | \
+ (((__u64)(x) & (__u64)0xff00000000000000ULL) >> 56)))
+
+#define ___constant_swahw32(x) ((__u32)( \
+ (((__u32)(x) & (__u32)0x0000ffffUL) << 16) | \
+ (((__u32)(x) & (__u32)0xffff0000UL) >> 16)))
+
+#define ___constant_swahb32(x) ((__u32)( \
+ (((__u32)(x) & (__u32)0x00ff00ffUL) << 8) | \
+ (((__u32)(x) & (__u32)0xff00ff00UL) >> 8)))
+
+/*
+ * Implement the following as inlines, but define the interface using
+ * macros to allow constant folding when possible:
+ * ___swab16, ___swab32, ___swab64, ___swahw32, ___swahb32
+ */
+
+static __inline__ __u16 __fswab16(__u16 val)
+{
+#if defined (__arch_swab16)
+ return __arch_swab16(val);
+#else
+ return ___constant_swab16(val);
+#endif
+}
+
+static __inline__ __u32 __fswab32(__u32 val)
+{
+#if defined(__arch_swab32)
+ return __arch_swab32(val);
+#else
+ return ___constant_swab32(val);
+#endif
+}
+
+static __inline__ __u64 __fswab64(__u64 val)
+{
+#if defined (__arch_swab64)
+ return __arch_swab64(val);
+#elif defined(__SWAB_64_THRU_32__)
+ __u32 h = val >> 32;
+ __u32 l = val & ((1ULL << 32) - 1);
+ return (((__u64)__fswab32(l)) << 32) | ((__u64)(__fswab32(h)));
+#else
+ return ___constant_swab64(val);
+#endif
+}
+
+static __inline__ __u32 __fswahw32(__u32 val)
+{
+#ifdef __arch_swahw32
+ return __arch_swahw32(val);
+#else
+ return ___constant_swahw32(val);
+#endif
+}
+
+static __inline__ __u32 __fswahb32(__u32 val)
+{
+#ifdef __arch_swahb32
+ return __arch_swahb32(val);
+#else
+ return ___constant_swahb32(val);
+#endif
+}
+
+/**
+ * __swab16 - return a byteswapped 16-bit value
+ * @x: value to byteswap
+ */
+#ifdef __HAVE_BUILTIN_BSWAP16__
+#define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
+#else
+#define __swab16(x) \
+ (__builtin_constant_p((__u16)(x)) ? \
+ ___constant_swab16(x) : \
+ __fswab16(x))
+#endif
+
+/**
+ * __swab32 - return a byteswapped 32-bit value
+ * @x: value to byteswap
+ */
+#ifdef __HAVE_BUILTIN_BSWAP32__
+#define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
+#else
+#define __swab32(x) \
+ (__builtin_constant_p((__u32)(x)) ? \
+ ___constant_swab32(x) : \
+ __fswab32(x))
+#endif
+
+/**
+ * __swab64 - return a byteswapped 64-bit value
+ * @x: value to byteswap
+ */
+#ifdef __HAVE_BUILTIN_BSWAP64__
+#define __swab64(x) (__u64)__builtin_bswap64((__u64)(x))
+#else
+#define __swab64(x) \
+ (__builtin_constant_p((__u64)(x)) ? \
+ ___constant_swab64(x) : \
+ __fswab64(x))
+#endif
+
+static __always_inline unsigned long __swab(const unsigned long y)
+{
+#if __BITS_PER_LONG == 64
+ return __swab64(y);
+#else /* __BITS_PER_LONG == 32 */
+ return __swab32(y);
+#endif
+}
+
+/**
+ * __swahw32 - return a word-swapped 32-bit value
+ * @x: value to wordswap
+ *
+ * __swahw32(0x12340000) is 0x00001234
+ */
+#define __swahw32(x) \
+ (__builtin_constant_p((__u32)(x)) ? \
+ ___constant_swahw32(x) : \
+ __fswahw32(x))
+
+/**
+ * __swahb32 - return a high and low byte-swapped 32-bit value
+ * @x: value to byteswap
+ *
+ * __swahb32(0x12345678) is 0x34127856
+ */
+#define __swahb32(x) \
+ (__builtin_constant_p((__u32)(x)) ? \
+ ___constant_swahb32(x) : \
+ __fswahb32(x))
+
+/**
+ * __swab16p - return a byteswapped 16-bit value from a pointer
+ * @p: pointer to a naturally-aligned 16-bit value
+ */
+static __always_inline __u16 __swab16p(const __u16 *p)
+{
+#ifdef __arch_swab16p
+ return __arch_swab16p(p);
+#else
+ return __swab16(*p);
+#endif
+}
+
+/**
+ * __swab32p - return a byteswapped 32-bit value from a pointer
+ * @p: pointer to a naturally-aligned 32-bit value
+ */
+static __always_inline __u32 __swab32p(const __u32 *p)
+{
+#ifdef __arch_swab32p
+ return __arch_swab32p(p);
+#else
+ return __swab32(*p);
+#endif
+}
+
+/**
+ * __swab64p - return a byteswapped 64-bit value from a pointer
+ * @p: pointer to a naturally-aligned 64-bit value
+ */
+static __always_inline __u64 __swab64p(const __u64 *p)
+{
+#ifdef __arch_swab64p
+ return __arch_swab64p(p);
+#else
+ return __swab64(*p);
+#endif
+}
+
+/**
+ * __swahw32p - return a wordswapped 32-bit value from a pointer
+ * @p: pointer to a naturally-aligned 32-bit value
+ *
+ * See __swahw32() for details of wordswapping.
+ */
+static __inline__ __u32 __swahw32p(const __u32 *p)
+{
+#ifdef __arch_swahw32p
+ return __arch_swahw32p(p);
+#else
+ return __swahw32(*p);
+#endif
+}
+
+/**
+ * __swahb32p - return a high and low byteswapped 32-bit value from a pointer
+ * @p: pointer to a naturally-aligned 32-bit value
+ *
+ * See __swahb32() for details of high/low byteswapping.
+ */
+static __inline__ __u32 __swahb32p(const __u32 *p)
+{
+#ifdef __arch_swahb32p
+ return __arch_swahb32p(p);
+#else
+ return __swahb32(*p);
+#endif
+}
+
+/**
+ * __swab16s - byteswap a 16-bit value in-place
+ * @p: pointer to a naturally-aligned 16-bit value
+ */
+static __inline__ void __swab16s(__u16 *p)
+{
+#ifdef __arch_swab16s
+ __arch_swab16s(p);
+#else
+ *p = __swab16p(p);
+#endif
+}
+/**
+ * __swab32s - byteswap a 32-bit value in-place
+ * @p: pointer to a naturally-aligned 32-bit value
+ */
+static __always_inline void __swab32s(__u32 *p)
+{
+#ifdef __arch_swab32s
+ __arch_swab32s(p);
+#else
+ *p = __swab32p(p);
+#endif
+}
+
+/**
+ * __swab64s - byteswap a 64-bit value in-place
+ * @p: pointer to a naturally-aligned 64-bit value
+ */
+static __always_inline void __swab64s(__u64 *p)
+{
+#ifdef __arch_swab64s
+ __arch_swab64s(p);
+#else
+ *p = __swab64p(p);
+#endif
+}
+
+/**
+ * __swahw32s - wordswap a 32-bit value in-place
+ * @p: pointer to a naturally-aligned 32-bit value
+ *
+ * See __swahw32() for details of wordswapping
+ */
+static __inline__ void __swahw32s(__u32 *p)
+{
+#ifdef __arch_swahw32s
+ __arch_swahw32s(p);
+#else
+ *p = __swahw32p(p);
+#endif
+}
+
+/**
+ * __swahb32s - high and low byteswap a 32-bit value in-place
+ * @p: pointer to a naturally-aligned 32-bit value
+ *
+ * See __swahb32() for details of high and low byte swapping
+ */
+static __inline__ void __swahb32s(__u32 *p)
+{
+#ifdef __arch_swahb32s
+ __arch_swahb32s(p);
+#else
+ *p = __swahb32p(p);
+#endif
+}
+
+
+#endif /* _LINUX_SWAB_H */
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