isa-l/crc/crc_ref.h

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#ifndef _CRC_REF_H
#define _CRC_REF_H

#ifdef __cplusplus
extern "C" {
#endif

#include "crc.h"

#ifdef _MSC_VER
#define inline __inline
#endif

#define MAX_ITER 8

// iSCSI CRC reference function
static inline unsigned int
crc32_iscsi_ref(unsigned char *buffer, int len, unsigned int crc_init)
{
        uint64_t rem = crc_init;
        int i, j;

        uint32_t poly = 0x82F63B78;

        for (i = 0; i < len; i++) {
                rem = rem ^ (buffer[i]);
                for (j = 0; j < MAX_ITER; j++) {
                        rem = (rem & 0x1ULL) ? (rem >> 1) ^ poly : (rem >> 1);
                }
        }
        return rem;
}

// crc16_t10dif reference function, slow crc16 from the definition.
static inline uint16_t
crc16_t10dif_ref(uint16_t seed, uint8_t *buf, uint64_t len)
{
        size_t rem = seed;
        unsigned int i, j;

        uint16_t poly = 0x8bb7; // t10dif standard

        for (i = 0; i < len; i++) {
                rem = rem ^ (buf[i] << 8);
                for (j = 0; j < MAX_ITER; j++) {
                        rem = rem << 1;
                        rem = (rem & 0x10000) ? rem ^ poly : rem;
                }
        }
        return rem;
}

// crc16_t10dif reference function, slow crc16 from the definition.
static inline uint16_t
crc16_t10dif_copy_ref(uint16_t seed, uint8_t *dst, uint8_t *src, uint64_t len)
{
        size_t rem = seed;
        unsigned int i, j;

        uint16_t poly = 0x8bb7; // t10dif standard

        for (i = 0; i < len; i++) {
                rem = rem ^ (src[i] << 8);
                dst[i] = src[i];
                for (j = 0; j < MAX_ITER; j++) {
                        rem = rem << 1;
                        rem = (rem & 0x10000) ? rem ^ poly : rem;
                }
        }
        return rem;
}

// crc32_ieee reference function, slow crc32 from the definition.
static inline uint32_t
crc32_ieee_ref(uint32_t seed, uint8_t *buf, uint64_t len)
{
        uint64_t rem = ~seed;
        unsigned int i, j;

        uint32_t poly = 0x04C11DB7; // IEEE standard

        for (i = 0; i < len; i++) {
                rem = rem ^ ((uint64_t) buf[i] << 24);
                for (j = 0; j < MAX_ITER; j++) {
                        rem = rem << 1;
                        rem = (rem & 0x100000000ULL) ? rem ^ poly : rem;
                }
        }
        return ~rem;
}

// crc32_gzip_refl reference function, slow crc32 from the definition.
// Please get difference details between crc32_gzip_ref and crc32_ieee
// from crc.h.
static inline uint32_t
crc32_gzip_refl_ref(uint32_t seed, uint8_t *buf, uint64_t len)
{
        uint64_t rem = ~seed;
        int i, j;

        uint32_t poly = 0xEDB88320; // IEEE standard

        for (i = 0; i < len; i++) {
                rem = rem ^ (buf[i]);
                for (j = 0; j < MAX_ITER; j++) {
                        rem = (rem & 0x1ULL) ? (rem >> 1) ^ poly : (rem >> 1);
                }
        }
        return ~rem;
}

#ifdef __cplusplus
}
#endif

#endif