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/*

 * CRC32 functions

 * Based on public domain implementation by Finn Yannick Jacobs.

 */

/* Written and copyright 1999 by Finn Yannick Jacobs

 * No rights were reserved to this, so feel free to

 * manipulate or do with it, what you want or desire :)

 */

#include "crc32.h"

/* crc32table[] built by crc32_init() */

static unsigned long crc32table[256];

/* Calculate crc32. Little endian.

 * Standard seed is 0xffffffff or 0.

 * Some implementations xor result with 0xffffffff after calculation.

 */

uint32_t crc32(void *data, unsigned int len, uint32_t seed)

{

    uint8_t *d = data;

    while (len--)

    {

        seed = ((seed >> 8) & 0x00FFFFFF) ^ crc32table [(seed ^ *d++) & 0xFF];

    }

    return seed;

}

/* Calculate crc32table */

void crc32_init()

{

    uint32_t poly = 0xEDB88320L;

    uint32_t crc;

    int i, j;

    for (i = 0; i < 256; ++i)

    {

        crc = i;

        for (j = 8; j > 0; --j)

        {

            crc = (crc >> 1) ^ ((crc & 1) ? poly : 0);

        }

        crc32table[i] = crc;

    }

}