Contiki-NG
random.c
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1 /*
2  * Copyright (c) 2018, Texas Instruments Incorporated - http://www.ti.com/
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  * notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  * notice, this list of conditions and the following disclaimer in the
12  * documentation and/or other materials provided with the distribution.
13  * 3. Neither the name of the copyright holder nor the names of its
14  * contributors may be used to endorse or promote products derived
15  * from this software without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
19  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
20  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
21  * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
26  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
28  * OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30  /**
31  * \addtogroup cc13xx-cc26xx-cpu
32  * @{
33  *
34  * \defgroup cc13xx-cc26xx-prng Pseudo Random Number Generator (PRNG) for CC13xx/CC26xx.
35  * @{
36  *
37  * Implementation based on Bob Jenkins' small noncryptographic PRNG.
38  * - http://burtleburtle.net/bob/rand/smallprng.html
39  *
40  * This file overrides os/lib/random.c. Note that the file name must
41  * match the original file for the override to work.
42  *
43  * \file
44  * Implementation of Pseudo Random Number Generator for CC13xx/CC26xx.
45  * \author
46  * Edvard Pettersen <e.pettersen@ti.com>
47  */
48 /*---------------------------------------------------------------------------*/
49 #include <contiki.h>
50 /*---------------------------------------------------------------------------*/
51 #include <stdint.h>
52 /*---------------------------------------------------------------------------*/
53 typedef struct {
54  uint32_t a;
55  uint32_t b;
56  uint32_t c;
57  uint32_t d;
58 } ranctx_t;
59 
60 static ranctx_t ranctx;
61 /*---------------------------------------------------------------------------*/
62 #define rot32(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
63 /*---------------------------------------------------------------------------*/
64 /**
65  * \brief Generates a new random number using the PRNG.
66  * \return The random number.
67  */
68 unsigned short
70 {
71  uint32_t e;
72 
73  e = ranctx.a - rot32(ranctx.b, 27);
74  ranctx.a = ranctx.b ^ rot32(ranctx.c, 17);
75  ranctx.b = ranctx.c + ranctx.d;
76  ranctx.c = ranctx.d + e;
77  ranctx.d = e + ranctx.a;
78 
79  return (unsigned short)ranctx.d;
80 }
81 /*---------------------------------------------------------------------------*/
82 /**
83  * \brief Initialize the PRNG.
84  * \param seed Seed for the PRNG.
85  */
86 void
87 random_init(unsigned short seed)
88 {
89  uint32_t i;
90 
91  ranctx.a = 0xf1ea5eed;
92  ranctx.b = ranctx.c = ranctx.d = (uint32_t)seed;
93  for(i = 0; i < 20; ++i) {
94  (void)random_rand();
95  }
96 }
97 /*---------------------------------------------------------------------------*/
98 /**
99  * @}
100  * @}
101  */
void random_init(unsigned short seed)
Seed the cc2538 random number generator.
Definition: random.c:84
unsigned short random_rand(void)
Generates a new random number using the cc2538 RNG.
Definition: random.c:58