hash.c

// Hashing function
// (C) 2016-2017 Ronsor.
#include <inttypes.h>
uint32_t rc_crc32(uint32_t crc, unsigned char *buf, size_t len)
{
	static uint32_t table[256];
	static int have_table = 0;
	uint32_t rem;
	uint8_t octet;
	int i, j;
	const char *p, *q;
 
	/* This check is not thread safe; there is no mutex. */
	if (have_table == 0) {
		/* Calculate CRC table. */
		for (i = 0; i < 256; i++) {
			rem = i;  /* remainder from polynomial division */
			for (j = 0; j < 8; j++) {
				if (rem & 1) {
					rem >>= 1;
					rem ^= 0xedb88320;
				} else
					rem >>= 1;
			}
			table[i] = rem;
		}
		have_table = 1;
	}
 
	crc = ~crc;
	q = buf + len;
	for (p = buf; p < q; p++) {
		octet = *p;  /* Cast to unsigned octet. */
		crc = (crc >> 8) ^ table[(crc & 0xff) ^ octet];
	}
	return ~crc;
}
 
char* str_crc32(unsigned char* data, int length){
	uint32_t ret = rc_crc32(0, data, length);
	char *res = malloc(32);
	//printf("%" PRIX32, ret);
	sprintf(res, "%" PRIX32, ret);
	return res;
}