prng.h

00001 /* prng.h -- Pseudo Random Numbers
00002  *
00003  * Copyright (C) 2010--2012 Olaf Bergmann <bergmann@tzi.org>
00004  *
00005  * This file is part of the library tinydtls. Please see
00006  * README for terms of use. 
00007  */
00008 
00009 /** 
00010  * @file prng.h
00011  * @brief Pseudo Random Numbers
00012  */
00013 
00014 #ifndef _DTLS_PRNG_H_
00015 #define _DTLS_PRNG_H_
00016 
00017 #include "config.h"
00018 
00019 /** 
00020  * @defgroup prng Pseudo Random Numbers
00021  * @{
00022  */
00023 
00024 #ifndef WITH_CONTIKI
00025 #include <stdlib.h>
00026 
00027 /**
00028  * Fills \p buf with \p len random bytes. This is the default
00029  * implementation for prng().  You might want to change prng() to use
00030  * a better PRNG on your specific platform.
00031  */
00032 static inline int
00033 dtls_prng_impl(unsigned char *buf, size_t len) {
00034   while (len--)
00035     *buf++ = rand() & 0xFF;
00036   return 1;
00037 }
00038 #else /* WITH_CONTIKI */
00039 #include <string.h>
00040 
00041 #ifdef HAVE_PRNG
00042 extern int contiki_prng_impl(unsigned char *buf, size_t len);
00043 #else
00044 /**
00045  * Fills \p buf with \p len random bytes. This is the default
00046  * implementation for prng().  You might want to change prng() to use
00047  * a better PRNG on your specific platform.
00048  */
00049 static inline int
00050 contiki_prng_impl(unsigned char *buf, size_t len) {
00051   unsigned short v = random_rand();
00052   while (len > sizeof(v)) {
00053     memcpy(buf, &v, sizeof(v));
00054     len -= sizeof(v);
00055     buf += sizeof(v);
00056     v = random_rand();
00057   }
00058 
00059   memcpy(buf, &v, len);
00060   return 1;
00061 }
00062 #endif /* HAVE_PRNG */
00063 
00064 #define prng(Buf,Length) contiki_prng_impl((Buf), (Length))
00065 #define prng_init(Value) random_init((unsigned short)(Value))
00066 #endif /* WITH_CONTIKI */
00067 
00068 #ifndef prng
00069 /** 
00070  * Fills \p Buf with \p Length bytes of random data. 
00071  * 
00072  * @hideinitializer
00073  */
00074 #define prng(Buf,Length) dtls_prng_impl((Buf), (Length))
00075 #endif
00076 
00077 #ifndef prng_init
00078 /** 
00079  * Called to set the PRNG seed. You may want to re-define this to
00080  * allow for a better PRNG.
00081  *
00082  * @hideinitializer
00083  */
00084 #define prng_init(Value) srand((unsigned long)(Value))
00085 #endif
00086 
00087 /** @} */
00088 
00089 #endif /* _DTLS_PRNG_H_ */