CRC8 implementation in C

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>

/*
 * 1 + x + x^3
 */
#define POLYNOMIAL 0b101
#define MAX_u8 0xFF

void test_crc();
bool contains_in_array(uint8_t* arr, uint8_t size, uint8_t number);

uint8_t calc_crc(uint8_t* data, uint8_t size, uint8_t polynomial);

int main() {
	test_crc();

	char str[512];
	printf("Enter text for calculate CRC8: ");
	gets(str);
	size_t str_len = strlen(str);

	printf("Entered text: %s\n", str);
	printf("CRC8 of entered text: 0x%X\n", calc_crc((uint8_t*)str, str_len, POLYNOMIAL));
}

void test_crc() {
	printf("Testing CRC for numbers in range [0; %u]\n", MAX_u8);
	uint8_t* crc = malloc(MAX_u8 + 1);
	uint8_t array_size = 0;

	uint8_t collysion = 0;
	for (int i = 0; i <= MAX_u8; i++) {
		uint8_t current_crc = calc_crc(&(uint8_t)i, 1, POLYNOMIAL);
		if (contains_in_array(crc, array_size, current_crc)) {
			collysion++;
		}
		else {
			crc[array_size++] = current_crc;
		}
	}

	free(crc);

	printf("Amount collysions: %d\n", collysion);
	printf("Collysion rate: %d%%\n", (uint8_t)((100 * collysion) / MAX_u8));
}

bool contains_in_array(uint8_t* arr, uint8_t size, uint8_t number) {
	for (uint8_t i = 0; i < size; i++)
		if (arr[i] == number)
			return true;
	return false;
}

uint8_t calc_crc(uint8_t* data, uint8_t size, uint8_t polynomial) {
	uint8_t crc = 0x00;
	for (uint8_t i = 0; i < size; i++) {
		crc ^= data[i];
		for (uint8_t j = 0; j < 8; j++) {
			crc = (crc & 0x80) != 0 ? (crc << 1) ^ polynomial : crc << 1;
		}
	}

	return crc;
}