1 /*
2 * prng.h -- Pseudo Random Numbers
3 *
4 * Copyright (C) 2010-2011 Olaf Bergmann <bergmann@tzi.org>
5 *
6 * This file is part of the CoAP library libcoap. Please see README for terms
7 * of use.
8 */
9
10 /**
11 * @file prng.h
12 * @brief Pseudo Random Numbers
13 */
14
15 #ifndef _COAP_PRNG_H_
16 #define _COAP_PRNG_H_
17
18 /**
19 * @defgroup prng Pseudo Random Numbers
20 * @{
21 */
22
23 #if defined(WITH_POSIX) || (defined(WITH_LWIP) && !defined(LWIP_RAND))
24 #include <stdlib.h>
25
26 /**
27 * Fills \p buf with \p len random bytes. This is the default implementation for
28 * prng(). You might want to change prng() to use a better PRNG on your specific
29 * platform.
30 */
31 static inline int
coap_prng_impl(unsigned char * buf,size_t len)32 coap_prng_impl(unsigned char *buf, size_t len) {
33 while (len--)
34 *buf++ = rand() & 0xFF;
35 return 1;
36 }
37 #endif /* WITH_POSIX */
38
39 #ifdef WITH_CONTIKI
40 #include <string.h>
41
42 /**
43 * Fills \p buf with \p len random bytes. This is the default implementation for
44 * prng(). You might want to change prng() to use a better PRNG on your specific
45 * platform.
46 */
47 static inline int
contiki_prng_impl(unsigned char * buf,size_t len)48 contiki_prng_impl(unsigned char *buf, size_t len) {
49 unsigned short v = random_rand();
50 while (len > sizeof(v)) {
51 memcpy(buf, &v, sizeof(v));
52 len -= sizeof(v);
53 buf += sizeof(v);
54 v = random_rand();
55 }
56
57 memcpy(buf, &v, len);
58 return 1;
59 }
60
61 #define prng(Buf,Length) contiki_prng_impl((Buf), (Length))
62 #define prng_init(Value) random_init((unsigned short)(Value))
63 #endif /* WITH_CONTIKI */
64
65 #if defined(WITH_LWIP) && defined(LWIP_RAND)
66 static inline int
lwip_prng_impl(unsigned char * buf,size_t len)67 lwip_prng_impl(unsigned char *buf, size_t len) {
68 u32_t v = LWIP_RAND();
69 while (len > sizeof(v)) {
70 memcpy(buf, &v, sizeof(v));
71 len -= sizeof(v);
72 buf += sizeof(v);
73 v = LWIP_RAND();
74 }
75
76 memcpy(buf, &v, len);
77 return 1;
78 }
79
80 #define prng(Buf,Length) lwip_prng_impl((Buf), (Length))
81 #define prng_init(Value)
82
83 #endif /* WITH_LWIP */
84
85 #ifndef prng
86 /**
87 * Fills \p Buf with \p Length bytes of random data.
88 *
89 * @hideinitializer
90 */
91 #define prng(Buf,Length) coap_prng_impl((Buf), (Length))
92 #endif
93
94 #ifndef prng_init
95 /**
96 * Called to set the PRNG seed. You may want to re-define this to allow for a
97 * better PRNG.
98 *
99 * @hideinitializer
100 */
101 #define prng_init(Value) srand((unsigned long)(Value))
102 #endif
103
104 /** @} */
105
106 #endif /* _COAP_PRNG_H_ */
107
