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Commit a5cfc1ec authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
Browse files

[PATCH] bit reverse library 



This patch provides two bit reverse functions and bit reverse table.

- reverse the order of bits in a u32 value

	u8 bitrev8(u8 x);

- reverse the order of bits in a u32 value

	u32 bitrev32(u32 x);

- byte reverse table

	const u8 byte_rev_table[256];

Signed-off-by: default avatarAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 30e25b71

include/linux/bitrev.h

0 → 100644
+15 −0
Original line number Diff line number Diff line 
#ifndef _LINUX_BITREV_H

#define _LINUX_BITREV_H



#include <linux/types.h>



extern u8 const byte_rev_table[256];



static inline u8 bitrev8(u8 byte)

{

	return byte_rev_table[byte];

}



extern u32 bitrev32(u32 in);



#endif /* _LINUX_BITREV_H */

lib/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -4,6 +4,9 @@ 


menu "Library routines"



config BITREVERSE

	tristate



config CRC_CCITT

	tristate "CRC-CCITT functions"

	help

lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ ifneq ($(CONFIG_HAVE_DEC_LOCK),y) 
  lib-y += dec_and_lock.o

endif



obj-$(CONFIG_BITREVERSE) += bitrev.o

obj-$(CONFIG_CRC_CCITT)	+= crc-ccitt.o

obj-$(CONFIG_CRC16)	+= crc16.o

obj-$(CONFIG_CRC32)	+= crc32.o

lib/bitrev.c

0 → 100644
+54 −0
Original line number Diff line number Diff line 
#include <linux/types.h>

#include <linux/module.h>

#include <linux/bitrev.h>



const u8 byte_rev_table[256] = {

	0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,

	0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,

	0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,

	0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,

	0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,

	0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,

	0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,

	0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,

	0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,

	0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,

	0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,

	0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,

	0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,

	0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,

	0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,

	0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,

	0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,

	0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,

	0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,

	0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,

	0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,

	0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,

	0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,

	0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,

	0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,

	0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,

	0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,

	0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,

	0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,

	0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,

	0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,

	0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff,

};

EXPORT_SYMBOL_GPL(byte_rev_table);



static __always_inline u16 bitrev16(u16 x)

{

	return (bitrev8(x & 0xff) << 8) | bitrev8(x >> 8);

}



/**

 * bitrev32 - reverse the order of bits in a u32 value

 * @x: value to be bit-reversed

 */

u32 bitrev32(u32 x)

{

	return (bitrev16(x & 0xffff) << 16) | bitrev16(x >> 16);

}

EXPORT_SYMBOL(bitrev32);