[PATCH v2 07/11] lib: add bitrev8x4()

From	Alan Tull <atull@kernel.org>
Newsgroups	linux.kernel
Subject	[PATCH v2 07/11] lib: add bitrev8x4()
Date	2017-06-14 17:40 +0200
Message-ID	<tSiyK-6WY-27@gated-at.bofh.it> (permalink)
References	<tSiyJ-6WY-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

From: Joshua Clayton <stillcompiling@gmail.com>

Add a function to reverse bytes within a 32 bit word.
Operate on a u32 rather than individual bytes.

Signed-off-by: Joshua Clayton <stillcompiling@gmail.com>
Signed-off-by: Alan Tull <atull@kernel.org>
---
 include/linux/bitrev.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/linux/bitrev.h b/include/linux/bitrev.h
index fb790b8..b97be27 100644
--- a/include/linux/bitrev.h
+++ b/include/linux/bitrev.h
@@ -29,6 +29,8 @@ static inline u32 __bitrev32(u32 x)
 
 #endif /* CONFIG_HAVE_ARCH_BITREVERSE */
 
+#define __bitrev8x4(x)	(__bitrev32(swab32(x)))
+
 #define __constant_bitrev32(x)	\
 ({					\
 	u32 __x = x;			\
@@ -50,6 +52,15 @@ static inline u32 __bitrev32(u32 x)
 	__x;								\
 })
 
+#define __constant_bitrev8x4(x) \
+({			\
+	u32 __x = x;	\
+	__x = ((__x & (u32)0xF0F0F0F0UL) >> 4) | ((__x & (u32)0x0F0F0F0FUL) << 4);	\
+	__x = ((__x & (u32)0xCCCCCCCCUL) >> 2) | ((__x & (u32)0x33333333UL) << 2);	\
+	__x = ((__x & (u32)0xAAAAAAAAUL) >> 1) | ((__x & (u32)0x55555555UL) << 1);	\
+	__x;								\
+})
+
 #define __constant_bitrev8(x)	\
 ({					\
 	u8 __x = x;			\
@@ -75,6 +86,14 @@ static inline u32 __bitrev32(u32 x)
 	__bitrev16(__x);				\
  })
 
+#define bitrev8x4(x) \
+({			\
+	u32 __x = x;	\
+	__builtin_constant_p(__x) ?	\
+	__constant_bitrev8x4(__x) :			\
+	__bitrev8x4(__x);				\
+ })
+
 #define bitrev8(x) \
 ({			\
 	u8 __x = x;	\
-- 
2.7.4

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH v2 07/11] lib: add bitrev8x4() Alan Tull <atull@kernel.org> - 2017-06-14 17:40 +0200

csiph-web