linux-master/lib/crc32.c

58 crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
61 #  define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8)
67 #  define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
106 		q = crc ^ *++b; /* use pre increment for speed */
108 		crc = DO_CRC4;
110 		crc = DO_CRC8;
112 		crc ^= DO_CRC4;
128 	return crc;
139  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for other
146 static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p,
153 		crc ^= *p++;
155 			crc = (crc >> 1) ^ ((crc & 1) ? polynomial : 0);
159 		crc ^= *p++;
160 		crc = (crc >> 2) ^ tab[0][crc & 3];
161 		crc = (crc >> 2) ^ tab[0][crc & 3];
162 		crc = (crc >> 2) ^ tab[0][crc & 3];
163 		crc = (crc >> 2) ^ tab[0][crc & 3];
167 		crc ^= *p++;
168 		crc = (crc >> 4) ^ tab[0][crc & 15];
169 		crc = (crc >> 4) ^ tab[0][crc & 15];
174 		crc ^= *p++;
175 		crc = (crc >> 8) ^ tab[0][crc & 255];
178 	crc = (__force u32) __cpu_to_le32(crc);
179 	crc = crc32_body(crc, p, len, tab);
180 	crc = __le32_to_cpu((__force __le32)crc);
182 	return crc;
186 u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len)
188 	return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE);
190 u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len)
192 	return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE);
195 u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len)
197 	return crc32_le_generic(crc, p, len, crc32table_le, CRC32_POLY_LE);
199 u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len)
201 	return crc32_le_generic(crc, p, len, crc32ctable_le, CRC32C_POLY_LE);
231  * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time
232  * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient)
233  * @len: The number of bytes. @crc is multiplied by x^(8*@len)
242 static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len,
250 		crc = (crc >> 1) ^ (crc & 1 ? polynomial : 0);
254 		return crc;
259 			crc = gf2_multiply(crc, power, polynomial);
269 	return crc;
272 u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len)
274 	return crc32_generic_shift(crc, len, CRC32_POLY_LE);
277 u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len)
279 	return crc32_generic_shift(crc, len, CRC32C_POLY_LE);
286  * @crc: seed value for computation.  ~0 for Ethernet, sometimes 0 for
293 static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p,
300 		crc ^= *p++ << 24;
302 			crc =
303 			    (crc << 1) ^ ((crc & 0x80000000) ? polynomial :
308 		crc ^= *p++ << 24;
309 		crc = (crc << 2) ^ tab[0][crc >> 30];
310 		crc = (crc << 2) ^ tab[0][crc >> 30];
311 		crc = (crc << 2) ^ tab[0][crc >> 30];
312 		crc = (crc << 2) ^ tab[0][crc >> 30];
316 		crc ^= *p++ << 24;
317 		crc = (crc << 4) ^ tab[0][crc >> 28];
318 		crc = (crc << 4) ^ tab[0][crc >> 28];
322 		crc ^= *p++ << 24;
323 		crc = (crc << 8) ^ tab[0][crc >> 24];
326 	crc = (__force u32) __cpu_to_be32(crc);
327 	crc = crc32_body(crc, p, len, tab);
328 	crc = __be32_to_cpu((__force __be32)crc);
330 	return crc;
334 u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len)
336 	return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE);
339 u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len)
341 	return crc32_be_generic(crc, p, len, crc32table_be, CRC32_POLY_BE);