Merge pull request #4079 from kaspar030/add_minstd_prng

sys: random: modularize PRNG module, add LCG alternatives

Makefile.pseudomodules

@@ -23,3 +23,6 @@ PSEUDOMODULES += netif
 # include variants of the AT86RF2xx drivers as pseudo modules
 PSEUDOMODULES += at86rf23%
 PSEUDOMODULES += at86rf21%
+
+# add all pseudo random number generator variants as pseudomodules
+PSEUDOMODULES += prng_%

sys/include/div.h

@@ -77,6 +77,28 @@ static inline uint32_t div_u32_by_15625div512(uint32_t val)
     return ((uint64_t)(val) * 0x431bde83ul) >> (12 + 32 - 9);
 }
 
+/**
+ * @brief Integer divide val by 44488
+ *
+ * @param[in]   val     dividend
+ * @return      (val / 44488)
+ */
+static inline uint32_t div_u32_by_44488(uint32_t val)
+{
+    return ((uint64_t)val * 0xBC8F1391UL) >> (15 + 32);
+}
+
+/**
+ * @brief Modulo 44488
+ *
+ * @param[in]   val     dividend
+ * @return      (val % 44488)
+ */
+static inline uint32_t div_u32_mod_44488(uint32_t val)
+{
+    return val - (div_u32_by_44488(val)*44488);
+}
+
 #ifdef __cplusplus
 }
 #endif

sys/random/Makefile

+ifeq (,$(filter prng_%,$(USEMODULE)))
+    USEMODULE += prng_mersenne
+endif
+ifneq (,$(filter prng_mersenne,$(USEMODULE)))
+    SRC += mersenne.c
+endif
+ifneq (,$(filter prng_minstd,$(USEMODULE)))
+    SRC += minstd.c
+endif
+ifneq (,$(filter prng_musl_lcg,$(USEMODULE)))
+    SRC += musl_lcg.c
+endif
+
 include $(RIOTBASE)/Makefile.base

sys/random/minstd.c

+/**
+ * Copyright (C) 2015 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 C FAQ (http://c-faq.com/lib/rand.html).
+ */
+
+ /**
+ * @ingroup sys_random
+ * @{
+ * @file
+ *
+ * @brief Simple Park & Miller "minimal standard" PRNG
+ *
+ * This file contains a simple Park-Miller pseudo random number generator.
+ *
+ * While not very random when considering crypto requirements, this is probably
+ * random enough anywhere where pseudo-randomness is sufficient, e.g., when
+ * provided with a sensible seed source, for MAC algorithms.
+ *
+ * The implementation is taken from the C FAQ, but modified to use magic number
+ * division and adapted to RIOT's coding conventions..
+ *
+ * @author Kaspar Schleiser <kaspar@schleiser.de>
+ * @}
+ */
+
+#include <stdint.h>
+
+#include "div.h"
+
+#define a 48271
+#define m 2147483647
+#define q (m / a) /* 44488 */
+#define r (m % a) /* 3399 */
+
+static uint32_t _seed = 1;
+
+int rand_minstd(void)
+{
+    uint32_t hi = div_u32_by_44488(_seed);
+    uint32_t lo = div_u32_mod_44488(_seed);
+    uint32_t test = (a * lo) - (r * hi);
+
+    if(test > 0) {
+        _seed = test;
+    }
+    else {
+        _seed = test + m;
+    }
+
+    return _seed;
+}
+
+uint32_t genrand_uint32(void)
+{
+    /* minstd as implemented returns only values from 1 to 2147483647,
+     * so run it two times to get 32bits */
+    uint16_t A = (rand_minstd() >> 15);
+    uint16_t B = (rand_minstd() >> 15);
+    return  (((uint32_t)A) << 16) | B;
+}
+
+void genrand_init(uint32_t val)
+{
+    if (!val) {
+        val = 1;
+    }
+    _seed = val;
+}

sys/random/musl_lcg.c

+/**
+ * Copyright (C) 2015 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 Musl C library. Original copyright notice:
+ *
+ * Copyright © 2005-2014 Rich Felker, et al.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <stdint.h>
+
+static uint64_t _seed;
+
+void genrand_init(uint32_t s)
+{
+    _seed = s-1;
+}
+
+uint32_t genrand_uint32(void)
+{
+    _seed = 6364136223846793005ULL*_seed + 1;
+    return _seed>>32;
+}

sys/shell/commands/Makefile

@@ -21,7 +21,7 @@ ifneq (,$(filter lpc2387,$(USEMODULE)))
   SRC += sc_heap.c
 endif
 ifneq (,$(filter random,$(USEMODULE)))
-  SRC += sc_mersenne.c
+  SRC += sc_random.c
 endif
 ifeq ($(CPU),x86)
   SRC += sc_x86_lspci.c

sys/shell/commands/sc_mersenne.c → sys/shell/commands/sc_random.c

@@ -12,7 +12,7 @@
  * @{
  *
  * @file
- * @brief       Shell commands for mersenne twister
+ * @brief       Shell commands for random generators
  *
  * @author      Christian Mehlis <mehlis@inf.fu-berlin.de>
  * @author      Kaspar Schleiser <kaspar@schleiser.de>
@@ -30,7 +30,7 @@
 
 #include "random.h"
 
-int _mersenne_init(int argc, char **argv)
+int _random_init(int argc, char **argv)
 {
     int initval;
 
@@ -53,7 +53,7 @@ int _mersenne_init(int argc, char **argv)
     return 0;
 }
 
-int _mersenne_get(int argc, char **argv)
+int _random_get(int argc, char **argv)
 {
     (void) argc;
     (void) argv;

sys/shell/commands/shell_commands.c

@@ -96,8 +96,8 @@ extern int _icmpv6_ping(int argc, char **argv);
 #endif
 
 #ifdef MODULE_RANDOM
-extern int _mersenne_init(int argc, char **argv);
-extern int _mersenne_get(int argc, char **argv);
+extern int _random_init(int argc, char **argv);
+extern int _random_get(int argc, char **argv);
 #endif
 
 #ifdef MODULE_GNRC_NETIF
@@ -187,8 +187,8 @@ const shell_command_t _shell_command_list[] = {
 #endif
 #endif
 #ifdef MODULE_RANDOM
-    { "mersenne_init", "initializes the PRNG", _mersenne_init },
-    { "mersenne_get", "returns 32 bit of pseudo randomness", _mersenne_get },
+    { "random_init", "initializes the PRNG", _random_init },
+    { "random_get", "returns 32 bit of pseudo randomness", _random_get },
 #endif
 #if FEATURE_PERIPH_RTC
     {"rtc", "control RTC peripheral interface",  _rtc_handler},