crc64.c

/*
 * CDDL HEADER START
 *
 * This file and its contents are supplied under the terms of the
 * Common Development and Distribution License ("CDDL"), version 1.0.
 * You may only use this file in accordance with the terms of version
 * 1.0 of the CDDL.
 *
 * A full copy of the text of the CDDL should have accompanied this
 * source.  A copy of the CDDL is also available via the Internet at
 * http://www.illumos.org/license/CDDL.
 *
 * CDDL HEADER END
*/
/*
 * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
 */
/*
 * Copyright 2023 Saso Kiselkov. All rights reserved.
 */
 
#include <math.h>
 
#include <acfutils/crc64.h>
 
#define CRC64_POLY  0xC96C5795D7870F42ULL
 
static uint64_t crc64_table[256];
static uint64_t rand_seed = 0;
 
void
crc64_init(void)
{
    for (int i = 0; i < 256; i++) {
        uint64_t *ct;
        int j;
        for (ct = crc64_table + i, *ct = i, j = 8; j > 0; j--)
            *ct = (*ct >> 1) ^ (-(*ct & 1) & CRC64_POLY);
    }
}
 
void
crc64_state_init_impl(uint64_t *crc)
{
    ASSERT(crc != NULL);
    crc64_state_init(crc);
}
 
uint64_t
crc64(const void *input, size_t sz)
{
    uint64_t crc;
 
    crc64_state_init(&crc);
    return (crc64_append(crc, input, sz));
}
 
uint64_t
crc64_append(uint64_t crc, const void *input, size_t sz)
{
    const uint8_t *in_bytes = input;
 
    ASSERT3U(crc64_table[128], ==, CRC64_POLY);
    for (size_t i = 0; i < sz; i++)
        crc = (crc >> 8) ^ crc64_table[(crc ^ in_bytes[i]) & 0xFF];
 
    return (crc);
}
 
void
crc64_srand(uint64_t seed)
{
    rand_seed = seed;
}
 
uint64_t
crc64_rand(void)
{
    rand_seed = crc64(&rand_seed, sizeof (rand_seed));
    return (rand_seed);
}
 
double
crc64_rand_fract(void)
{
    return (crc64_rand() / (double)UINT64_MAX);
}
 
double
crc64_rand_normal(double sigma)
{
    double x = crc64_rand_fract();
    double y = crc64_rand_fract();
    double z = sqrt(-2 * log(x)) * cos(2 * M_PI * y);
    return (sigma * z);
}