Introduce a random module that is a subset of CPython's random. It

also initializes in the same way where it takes from a true random
source when available through os.urandom(). After initializing, it
produces deterministic results until the seed is set.

This replaces urandom!

Fixes #139.

1 files changed, 130 insertions, 0 deletions

diff --git a/shared-module/random/__init__.c b/shared-module/random/__init__.c
new file mode 100644
index 000000000..5cc20e5b5
--- /dev/null
+++ b/shared-module/random/__init__.c
@@ -0,0 +1,130 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Paul Sokolovsky
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * 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/runtime.h"
+#include "shared-bindings/os/__init__.h"
+#include "shared-bindings/time/__init__.h"
+
+// 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;
+
+STATIC uint32_t yasmarang(void)
+{
+    if (yasmarang_pad == 0xeda4baba) {
+        if (!common_hal_os_urandom((uint8_t *)&yasmarang_pad, sizeof(uint32_t))) {
+            yasmarang_pad = common_hal_time_monotonic() & 0xffffffff;
+        }
+    }
+   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
+
+// returns an unsigned integer below the given argument
+// n must not be zero
+STATIC uint32_t yasmarang_randbelow(uint32_t n) {
+    uint32_t mask = 1;
+    while ((n & mask) < n) {
+        mask = (mask << 1) | 1;
+    }
+    uint32_t r;
+    do {
+        r = yasmarang() & mask;
+    } while (r >= n);
+    return r;
+}
+
+void shared_modules_random_seed(mp_uint_t seed) {
+    yasmarang_pad = seed;
+    yasmarang_n = 69;
+    yasmarang_d = 233;
+    yasmarang_dat = 0;
+}
+
+mp_uint_t shared_modules_random_getrandbits(uint8_t n) {
+    uint32_t mask = ~0;
+    // Beware of C undefined behavior when shifting by >= than bit size
+    mask >>= (32 - n);
+    return yasmarang() & mask;
+}
+
+mp_int_t shared_modules_random_randrange(mp_int_t start, mp_int_t stop, mp_int_t step) {
+    mp_int_t n;
+    if (step > 0) {
+        n = (stop - start + step - 1) / step;
+    } else {
+        n = (stop - start + step + 1) / step;
+    }
+    return start + step * yasmarang_randbelow(n);
+}
+
+// returns a number in the range [0..1) using Yasmarang to fill in the fraction bits
+STATIC mp_float_t yasmarang_float(void) {
+    #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+    typedef uint64_t mp_float_int_t;
+    #elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
+    typedef uint32_t mp_float_int_t;
+    #endif
+    union {
+        mp_float_t f;
+        #if MP_ENDIANNESS_LITTLE
+        struct { mp_float_int_t frc:MP_FLOAT_FRAC_BITS, exp:MP_FLOAT_EXP_BITS, sgn:1; } p;
+        #else
+        struct { mp_float_int_t sgn:1, exp:MP_FLOAT_EXP_BITS, frc:MP_FLOAT_FRAC_BITS; } p;
+        #endif
+    } u;
+    u.p.sgn = 0;
+    u.p.exp = (1 << (MP_FLOAT_EXP_BITS - 1)) - 1;
+    if (MP_FLOAT_FRAC_BITS <= 32) {
+        u.p.frc = yasmarang();
+    } else {
+        u.p.frc = ((uint64_t)yasmarang() << 32) | (uint64_t)yasmarang();
+    }
+    return u.f - 1;
+}
+
+mp_float_t shared_modules_random_random(void) {
+    return yasmarang_float();
+}
+
+mp_float_t shared_modules_random_uniform(mp_float_t a, mp_float_t b) {
+    return a + (b - a) * yasmarang_float();
+}