/* * Aug 8, 2011 Bob Pearson with help from Joakim Tjernlund and George Spelvin * cleaned up code to current version of sparse and added the slicing-by-8 * algorithm to the closely similar existing slicing-by-4 algorithm. * * Oct 15, 2000 Matt Domsch <[email protected]> * Nicer crc32 functions/docs submitted by [email protected]. Thanks! * Code was from the public domain, copyright abandoned. Code was * subsequently included in the kernel, thus was re-licensed under the * GNU GPL v2. * * Oct 12, 2000 Matt Domsch <[email protected]> * Same crc32 function was used in 5 other places in the kernel. * I made one version, and deleted the others. * There are various incantations of crc32(). Some use a seed of 0 or ~0. * Some xor at the end with ~0. The generic crc32() function takes * seed as an argument, and doesn't xor at the end. Then individual * users can do whatever they need. * drivers/net/smc9194.c uses seed ~0, doesn't xor with ~0. * fs/jffs2 uses seed 0, doesn't xor with ~0. * fs/partitions/efi.c uses seed ~0, xor's with ~0. * * This source code is licensed under the GNU General Public License, * Version 2. See the file COPYING for more details. */ /* see: Documentation/staging/crc32.rst for a description of algorithms */ #include <linux/crc32.h> #include <linux/crc32poly.h> #include <linux/module.h> #include <linux/types.h> #include <linux/sched.h> #include "crc32defs.h" #if CRC_LE_BITS > 8 #define tole(x) … #else #define tole … #endif #if CRC_BE_BITS > 8 #define tobe(x) … #else #define tobe … #endif #include "crc32table.h" MODULE_AUTHOR(…) …; MODULE_DESCRIPTION(…) …; MODULE_LICENSE(…) …; #if CRC_LE_BITS > 8 || CRC_BE_BITS > 8 /* implements slicing-by-4 or slicing-by-8 algorithm */ static inline u32 __pure crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256]) { … } #endif /** * crc32_le_generic() - Calculate bitwise little-endian Ethernet AUTODIN II * CRC32/CRC32C * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for other * uses, or the previous crc32/crc32c value if computing incrementally. * @p: pointer to buffer over which CRC32/CRC32C is run * @len: length of buffer @p * @tab: little-endian Ethernet table * @polynomial: CRC32/CRC32c LE polynomial */ static inline u32 __pure crc32_le_generic(u32 crc, unsigned char const *p, size_t len, const u32 (*tab)[256], u32 polynomial) { … } #if CRC_LE_BITS == 1 u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len) { return crc32_le_generic(crc, p, len, NULL, CRC32_POLY_LE); } u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) { return crc32_le_generic(crc, p, len, NULL, CRC32C_POLY_LE); } #else u32 __pure __weak crc32_le(u32 crc, unsigned char const *p, size_t len) { … } u32 __pure __weak __crc32c_le(u32 crc, unsigned char const *p, size_t len) { … } #endif EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); u32 __pure crc32_le_base(u32, unsigned char const *, size_t) __alias(crc32_le); u32 __pure __crc32c_le_base(u32, unsigned char const *, size_t) __alias(__crc32c_le); u32 __pure crc32_be_base(u32, unsigned char const *, size_t) __alias(crc32_be); /* * This multiplies the polynomials x and y modulo the given modulus. * This follows the "little-endian" CRC convention that the lsbit * represents the highest power of x, and the msbit represents x^0. */ static u32 __attribute_const__ gf2_multiply(u32 x, u32 y, u32 modulus) { … } /** * crc32_generic_shift - Append @len 0 bytes to crc, in logarithmic time * @crc: The original little-endian CRC (i.e. lsbit is x^31 coefficient) * @len: The number of bytes. @crc is multiplied by x^(8*@len) * @polynomial: The modulus used to reduce the result to 32 bits. * * It's possible to parallelize CRC computations by computing a CRC * over separate ranges of a buffer, then summing them. * This shifts the given CRC by 8*len bits (i.e. produces the same effect * as appending len bytes of zero to the data), in time proportional * to log(len). */ static u32 __attribute_const__ crc32_generic_shift(u32 crc, size_t len, u32 polynomial) { … } u32 __attribute_const__ crc32_le_shift(u32 crc, size_t len) { … } u32 __attribute_const__ __crc32c_le_shift(u32 crc, size_t len) { … } EXPORT_SYMBOL(…); EXPORT_SYMBOL(…); /** * crc32_be_generic() - Calculate bitwise big-endian Ethernet AUTODIN II CRC32 * @crc: seed value for computation. ~0 for Ethernet, sometimes 0 for * other uses, or the previous crc32 value if computing incrementally. * @p: pointer to buffer over which CRC32 is run * @len: length of buffer @p * @tab: big-endian Ethernet table * @polynomial: CRC32 BE polynomial */ static inline u32 __pure crc32_be_generic(u32 crc, unsigned char const *p, size_t len, const u32 (*tab)[256], u32 polynomial) { … } #if CRC_BE_BITS == 1 u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len) { return crc32_be_generic(crc, p, len, NULL, CRC32_POLY_BE); } #else u32 __pure __weak crc32_be(u32 crc, unsigned char const *p, size_t len) { … } #endif EXPORT_SYMBOL(…);
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