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Commit ddcaccbc authored by Joakim Tjernlund's avatar Joakim Tjernlund Committed by Linus Torvalds
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crc32: minor optimizations and cleanup 



Move common crc body to new function crc32_body() cleaup and micro
optimize crc32_body for speed and less size.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarJoakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 14f1b75b

lib/crc32.c

+44 −77
Original line number Diff line number Diff line
@@ -42,6 +42,48 @@ MODULE_AUTHOR("Matt Domsch <Matt_Domsch@dell.com>"); 
MODULE_DESCRIPTION("Ethernet CRC32 calculations");

MODULE_LICENSE("GPL");



#if CRC_LE_BITS == 8 || CRC_BE_BITS == 8



static inline u32

crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 *tab)

{

# ifdef __LITTLE_ENDIAN

#  define DO_CRC(x) crc = tab[(crc ^ (x)) & 255 ] ^ (crc >> 8)

# else

#  define DO_CRC(x) crc = tab[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)

# endif

	const u32 *b = (const u32 *)buf;

	size_t    rem_len;



	/* Align it */

	if (unlikely((long)b & 3 && len)) {

		u8 *p = (u8 *)b;

		do {

			DO_CRC(*p++);

		} while ((--len) && ((long)p)&3);

		b = (u32 *)p;

	}

	rem_len = len & 3;

	/* load data 32 bits wide, xor data 32 bits wide. */

	len = len >> 2;

	for (--b; len; --len) {

		crc ^= *++b; /* use pre increment for speed */

		DO_CRC(0);

		DO_CRC(0);

		DO_CRC(0);

		DO_CRC(0);

	}

	len = rem_len;

	/* And the last few bytes */

	if (len) {

		u8 *p = (u8 *)(b + 1) - 1;

		do {

			DO_CRC(*++p); /* use pre increment for speed */

		} while (--len);

	}

	return crc;

}

#endif

/**

 * crc32_le() - Calculate bitwise little-endian Ethernet AUTODIN II CRC32

 * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
@@ -72,48 +114,10 @@ u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len) 
u32 __pure crc32_le(u32 crc, unsigned char const *p, size_t len)

{

# if CRC_LE_BITS == 8

	const u32      *b =(u32 *)p;

	const u32      *tab = crc32table_le;



# ifdef __LITTLE_ENDIAN

#  define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)

# else

#  define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)

# endif



	crc = __cpu_to_le32(crc);

	/* Align it */

	if(unlikely(((long)b)&3 && len)){

		do {

			u8 *p = (u8 *)b;

			DO_CRC(*p++);

			b = (void *)p;

		} while ((--len) && ((long)b)&3 );

	}

	if(likely(len >= 4)){

		/* load data 32 bits wide, xor data 32 bits wide. */

		size_t save_len = len & 3;

	        len = len >> 2;

		--b; /* use pre increment below(*++b) for speed */

		do {

			crc ^= *++b;

			DO_CRC(0);

			DO_CRC(0);

			DO_CRC(0);

			DO_CRC(0);

		} while (--len);

		b++; /* point to next byte(s) */

		len = save_len;

	}

	/* And the last few bytes */

	if(len){

		do {

			u8 *p = (u8 *)b;

			DO_CRC(*p++);

			b = (void *)p;

		} while (--len);

	}



	crc = crc32_body(crc, p, len, tab);

	return __le32_to_cpu(crc);

#undef ENDIAN_SHIFT

#undef DO_CRC
@@ -170,47 +174,10 @@ u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len) 
u32 __pure crc32_be(u32 crc, unsigned char const *p, size_t len)

{

# if CRC_BE_BITS == 8

	const u32      *b =(u32 *)p;

	const u32      *tab = crc32table_be;



# ifdef __LITTLE_ENDIAN

#  define DO_CRC(x) crc = tab[ (crc ^ (x)) & 255 ] ^ (crc>>8)

# else

#  define DO_CRC(x) crc = tab[ ((crc >> 24) ^ (x)) & 255] ^ (crc<<8)

# endif



	crc = __cpu_to_be32(crc);

	/* Align it */

	if(unlikely(((long)b)&3 && len)){

		do {

			u8 *p = (u8 *)b;

			DO_CRC(*p++);

			b = (u32 *)p;

		} while ((--len) && ((long)b)&3 );

	}

	if(likely(len >= 4)){

		/* load data 32 bits wide, xor data 32 bits wide. */

		size_t save_len = len & 3;

	        len = len >> 2;

		--b; /* use pre increment below(*++b) for speed */

		do {

			crc ^= *++b;

			DO_CRC(0);

			DO_CRC(0);

			DO_CRC(0);

			DO_CRC(0);

		} while (--len);

		b++; /* point to next byte(s) */

		len = save_len;

	}

	/* And the last few bytes */

	if(len){

		do {

			u8 *p = (u8 *)b;

			DO_CRC(*p++);

			b = (void *)p;

		} while (--len);

	}

	crc = crc32_body(crc, p, len, tab);

	return __be32_to_cpu(crc);

#undef ENDIAN_SHIFT

#undef DO_CRC