extmod/modurandom: Add "urandom" module.

Seedable and reproducible pseudo-random number generator. Implemented
functions are getrandbits(n) (n <= 32) and seed().

The algorithm used is Yasmarang by Ilya Levin:
http://www.literatecode.com/yasmarang

1 files changed, 92 insertions, 0 deletions

diff --git a/extmod/modurandom.c b/extmod/modurandom.c
new file mode 100644
index 0000000000..fb85eddcb3
--- /dev/null
+++ b/extmod/modurandom.c
@@ -0,0 +1,92 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Paul Sokolovsky
+ *
+ * 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 <assert.h>
+#include <string.h>
+
+//#include "py/nlr.h"
+#include "py/runtime.h"
+
+#if MICROPY_PY_URANDOM
+
+// Yasmarang random number generator
+// by Ilya Levin
+// http://www.literatecode.com/yasmarang
+// Public Domain
+
+STATIC uint32_t yasmarang_pad = 0xeda4baba, yasmarang_n = 69, yasmarang_d = 233;
+STATIC uint8_t yasmarang_dat = 0;
+
+uint32_t yasmarang(void)
+{
+   yasmarang_pad += yasmarang_dat + yasmarang_d * yasmarang_n;
+   yasmarang_pad = (yasmarang_pad<<3) + (yasmarang_pad>>29);
+   yasmarang_n = yasmarang_pad | 2;
+   yasmarang_d ^= (yasmarang_pad<<31) + (yasmarang_pad>>1);
+   yasmarang_dat ^= (char) yasmarang_pad ^ (yasmarang_d>>8) ^ 1;
+
+   return (yasmarang_pad^(yasmarang_d<<5)^(yasmarang_pad>>18)^(yasmarang_dat<<1));
+}  /* yasmarang */
+
+// End of Yasmarang
+
+STATIC mp_obj_t mod_urandom_getrandbits(mp_obj_t num_in) {
+    int n = mp_obj_get_int(num_in);
+    if (n > 32 || n == 0) {
+        nlr_raise(mp_obj_new_exception(&mp_type_ValueError));
+    }
+    uint32_t mask = ~0;
+    // Beware of C undefined behavior when shifting by >= than bit size
+    mask >>= (32 - n);
+    return mp_obj_new_int_from_uint(yasmarang() & mask);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_urandom_getrandbits_obj, mod_urandom_getrandbits);
+
+STATIC mp_obj_t mod_urandom_seed(mp_obj_t seed_in) {
+    mp_uint_t seed = mp_obj_get_int_truncated(seed_in);
+    yasmarang_pad = seed;
+    yasmarang_n = 69;
+    yasmarang_d = 233;
+    yasmarang_dat = 0;
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_urandom_seed_obj, mod_urandom_seed);
+
+STATIC const mp_rom_map_elem_t mp_module_urandom_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_urandom) },
+    { MP_ROM_QSTR(MP_QSTR_getrandbits), MP_ROM_PTR(&mod_urandom_getrandbits_obj) },
+    { MP_ROM_QSTR(MP_QSTR_seed), MP_ROM_PTR(&mod_urandom_seed_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(mp_module_urandom_globals, mp_module_urandom_globals_table);
+
+const mp_obj_module_t mp_module_urandom = {
+    .base = { &mp_type_module },
+    .name = MP_QSTR_urandom,
+    .globals = (mp_obj_dict_t*)&mp_module_urandom_globals,
+};
+
+#endif //MICROPY_PY_URANDOM