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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;
    }
}