/*
 * Copyright (C) 2015-2020 "IoT.bzh"
 * Author: José Bollo <jose.bollo@iot.bzh>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <stdint.h>

/*
 * Returns a tiny hash value for the 'text'.
 *
 * Tiny hash function inspired from pearson
 */
uint8_t pearson4(const char *text)
{
	static uint8_t T[16] = {
		 4,  1,  6,  0,  9, 14, 11,  5,
		 2,  3, 12, 15, 10,  7,  8, 13
	};
	uint8_t r, c;

	for (r = 0; (c = (uint8_t)*text) ; text++) {
		r = T[r ^ (15 & c)];
		r = T[r ^ (c >> 4)];
	}
	return r; // % HEADCOUNT;
}