utils: use constant byte-order conversion

Simplifies portability and ensures that cpu_to_* can be used in const
declarations. If the architecture has special instructions, the compiler
should be able to detect the pattern and use them.

Signed-off-by: Felix Fietkau <nbd@nbd.name>

1 files changed, 33 insertions, 26 deletions

diff --git a/utils.h b/utils.h
index e72d947..aa480e2 100644
--- a/utils.h
+++ b/utils.h
@@ -81,16 +81,10 @@ int clock_gettime(int type, struct timespec *tv);
 #elif defined(__APPLE__)
 #include <machine/endian.h>
 #include <machine/byte_order.h>
-#define bswap_32(x) OSSwapInt32(x)
-#define bswap_64(x) OSSwapInt64(x)
 #elif defined(__FreeBSD__)
 #include <sys/endian.h>
-#define bswap_32(x) bswap32(x)
-#define bswap_64(x) bswap64(x)
 #else
 #include <machine/endian.h>
-#define bswap_32(x) swap32(x)
-#define bswap_64(x) swap64(x)
 #endif
 
 #ifndef __BYTE_ORDER
@@ -103,28 +97,41 @@ int clock_gettime(int type, struct timespec *tv);
 #define __LITTLE_ENDIAN LITTLE_ENDIAN
 #endif
 
+#define __constant_swap16(x) ((uint16_t)(				\
+	(((uint16_t)(x) & (uint16_t)0x00ffU) << 8) |			\
+	(((uint16_t)(x) & (uint16_t)0xff00U) >> 8)))
+
+#define __constant_swap32(x) ((uint32_t)(				\
+	(((uint32_t)(x) & (uint32_t)0x000000ffUL) << 24) |		\
+	(((uint32_t)(x) & (uint32_t)0x0000ff00UL) <<  8) |		\
+	(((uint32_t)(x) & (uint32_t)0x00ff0000UL) >>  8) |		\
+	(((uint32_t)(x) & (uint32_t)0xff000000UL) >> 24)))
+
+#define __constant_swap64(x) ((uint64_t)(				\
+	(((uint64_t)(x) & (uint64_t)0x00000000000000ffULL) << 56) |	\
+	(((uint64_t)(x) & (uint64_t)0x000000000000ff00ULL) << 40) |	\
+	(((uint64_t)(x) & (uint64_t)0x0000000000ff0000ULL) << 24) |	\
+	(((uint64_t)(x) & (uint64_t)0x00000000ff000000ULL) <<  8) |	\
+	(((uint64_t)(x) & (uint64_t)0x000000ff00000000ULL) >>  8) |	\
+	(((uint64_t)(x) & (uint64_t)0x0000ff0000000000ULL) >> 24) |	\
+	(((uint64_t)(x) & (uint64_t)0x00ff000000000000ULL) >> 40) |	\
+	(((uint64_t)(x) & (uint64_t)0xff00000000000000ULL) >> 56)))
+
+
 static inline uint16_t __u_bswap16(uint16_t val)
 {
 	return ((val >> 8) & 0xffu) | ((val & 0xffu) << 8);
 }
 
-#if _GNUC_MIN_VER(4, 2)
-#define __u_bswap32(x) __builtin_bswap32(x)
-#define __u_bswap64(x) __builtin_bswap64(x)
-#else
-#define __u_bswap32(x) bswap_32(x)
-#define __u_bswap64(x) bswap_64(x)
-#endif
-
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 
-#define cpu_to_be64(x) __u_bswap64(x)
-#define cpu_to_be32(x) __u_bswap32(x)
-#define cpu_to_be16(x) __u_bswap16((uint16_t) (x))
+#define cpu_to_be64(x) __constant_swap64(x)
+#define cpu_to_be32(x) __constant_swap32(x)
+#define cpu_to_be16(x) __constant_swap16(x)
 
-#define be64_to_cpu(x) __u_bswap64(x)
-#define be32_to_cpu(x) __u_bswap32(x)
-#define be16_to_cpu(x) __u_bswap16((uint16_t) (x))
+#define be64_to_cpu(x) __constant_swap64(x)
+#define be32_to_cpu(x) __constant_swap32(x)
+#define be16_to_cpu(x) __constant_swap16(x)
 
 #define cpu_to_le64(x) (x)
 #define cpu_to_le32(x) (x)
@@ -136,13 +143,13 @@ static inline uint16_t __u_bswap16(uint16_t val)
 
 #else /* __BYTE_ORDER == __LITTLE_ENDIAN */
 
-#define cpu_to_le64(x) __u_bswap64(x)
-#define cpu_to_le32(x) __u_bswap32(x)
-#define cpu_to_le16(x) __u_bswap16((uint16_t) (x))
+#define cpu_to_le64(x) __constant_swap64(x)
+#define cpu_to_le32(x) __constant_swap32(x)
+#define cpu_to_le16(x) __constant_swap16(x)
 
-#define le64_to_cpu(x) __u_bswap64(x)
-#define le32_to_cpu(x) __u_bswap32(x)
-#define le16_to_cpu(x) __u_bswap16((uint16_t) (x))
+#define le64_to_cpu(x) __constant_swap64(x)
+#define le32_to_cpu(x) __constant_swap32(x)
+#define le16_to_cpu(x) __constant_swap16(x)
 
 #define cpu_to_be64(x) (x)
 #define cpu_to_be32(x) (x)