The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/lib/crc32defs.h

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    1 /*
    2  * There are multiple 16-bit CRC polynomials in common use, but this is
    3  * *the* standard CRC-32 polynomial, first popularized by Ethernet.
    4  * x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0
    5  */
    6 #define CRCPOLY_LE 0xedb88320
    7 #define CRCPOLY_BE 0x04c11db7
    8 
    9 /*
   10  * This is the CRC32c polynomial, as outlined by Castagnoli.
   11  * x^32+x^28+x^27+x^26+x^25+x^23+x^22+x^20+x^19+x^18+x^14+x^13+x^11+x^10+x^9+
   12  * x^8+x^6+x^0
   13  */
   14 #define CRC32C_POLY_LE 0x82F63B78
   15 
   16 /* Try to choose an implementation variant via Kconfig */
   17 #ifdef CONFIG_CRC32_SLICEBY8
   18 # define CRC_LE_BITS 64
   19 # define CRC_BE_BITS 64
   20 #endif
   21 #ifdef CONFIG_CRC32_SLICEBY4
   22 # define CRC_LE_BITS 32
   23 # define CRC_BE_BITS 32
   24 #endif
   25 #ifdef CONFIG_CRC32_SARWATE
   26 # define CRC_LE_BITS 8
   27 # define CRC_BE_BITS 8
   28 #endif
   29 #ifdef CONFIG_CRC32_BIT
   30 # define CRC_LE_BITS 1
   31 # define CRC_BE_BITS 1
   32 #endif
   33 
   34 /*
   35  * How many bits at a time to use.  Valid values are 1, 2, 4, 8, 32 and 64.
   36  * For less performance-sensitive, use 4 or 8 to save table size.
   37  * For larger systems choose same as CPU architecture as default.
   38  * This works well on X86_64, SPARC64 systems. This may require some
   39  * elaboration after experiments with other architectures.
   40  */
   41 #ifndef CRC_LE_BITS
   42 #  ifdef CONFIG_64BIT
   43 #  define CRC_LE_BITS 64
   44 #  else
   45 #  define CRC_LE_BITS 32
   46 #  endif
   47 #endif
   48 #ifndef CRC_BE_BITS
   49 #  ifdef CONFIG_64BIT
   50 #  define CRC_BE_BITS 64
   51 #  else
   52 #  define CRC_BE_BITS 32
   53 #  endif
   54 #endif
   55 
   56 /*
   57  * Little-endian CRC computation.  Used with serial bit streams sent
   58  * lsbit-first.  Be sure to use cpu_to_le32() to append the computed CRC.
   59  */
   60 #if CRC_LE_BITS > 64 || CRC_LE_BITS < 1 || CRC_LE_BITS == 16 || \
   61         CRC_LE_BITS & CRC_LE_BITS-1
   62 # error "CRC_LE_BITS must be one of {1, 2, 4, 8, 32, 64}"
   63 #endif
   64 
   65 /*
   66  * Big-endian CRC computation.  Used with serial bit streams sent
   67  * msbit-first.  Be sure to use cpu_to_be32() to append the computed CRC.
   68  */
   69 #if CRC_BE_BITS > 64 || CRC_BE_BITS < 1 || CRC_BE_BITS == 16 || \
   70         CRC_BE_BITS & CRC_BE_BITS-1
   71 # error "CRC_BE_BITS must be one of {1, 2, 4, 8, 32, 64}"
   72 #endif

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