mirror of
https://github.com/RIOT-OS/RIOT.git
synced 2024-12-29 04:50:03 +01:00
72 lines
1.3 KiB
C
72 lines
1.3 KiB
C
/**
|
|
* Copyright (C) 2017 Kaspar Schleiser <kaspar@schleiser.de>
|
|
*
|
|
* This file is subject to the terms and conditions of the GNU Lesser
|
|
* General Public License v2.1. See the file LICENSE in the top level
|
|
* directory for more details.
|
|
*
|
|
* Code taken from Wikipedia (https://en.wikipedia.org/wiki/Xorshift)
|
|
*/
|
|
|
|
/**
|
|
* @ingroup sys_random
|
|
* @{
|
|
* @file
|
|
*
|
|
* @brief Xorshift random number generator implementation
|
|
*
|
|
* @author Kaspar Schleiser <kaspar@schleiser.de>
|
|
* @}
|
|
*/
|
|
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
|
|
#include "random.h"
|
|
|
|
/* The state word must be initialized to non-zero */
|
|
uint32_t xorshift32(uint32_t *state)
|
|
{
|
|
uint32_t x = *state;
|
|
|
|
x ^= x << 13;
|
|
x ^= x >> 17;
|
|
x ^= x << 5;
|
|
*state = x;
|
|
|
|
return x;
|
|
}
|
|
|
|
/* The state array must be initialized to not be all zero */
|
|
uint32_t xorshift128(uint32_t *state)
|
|
{
|
|
uint32_t t = state[3];
|
|
|
|
t ^= t << 11;
|
|
t ^= t >> 8;
|
|
state[3] = state[2];
|
|
state[2] = state[1];
|
|
state[1] = state[0];
|
|
t ^= state[0];
|
|
t ^= state[0] >> 19;
|
|
state[0] = t;
|
|
|
|
return t;
|
|
}
|
|
|
|
static uint32_t _state32;
|
|
|
|
uint32_t random_uint32(void)
|
|
{
|
|
return xorshift32(&_state32);
|
|
}
|
|
|
|
void random_init(uint32_t val)
|
|
{
|
|
printf("random init %u\n", (unsigned)val);
|
|
if (!val) {
|
|
val = 1;
|
|
}
|
|
_state32 = val;
|
|
}
|