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.

2 files changed, 228 insertions, 0 deletions

diff --git a/shared-bindings/random/__init__.c b/shared-bindings/random/__init__.c
new file mode 100644
index 000000000..fe52c1fc0
--- /dev/null
+++ b/shared-bindings/random/__init__.c
@@ -0,0 +1,188 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 Paul Sokolovsky
+ * Copyright (c) 2016 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/obj.h"
+#include "py/runtime.h"
+#include "shared-bindings/random/__init__.h"
+
+//| :mod:`random` --- psuedo-random numbers and choices
+//| ========================================================
+//|
+//| .. module:: random
+//|   :synopsis: psuedo-random numbers and choices
+//|   :platform: SAMD21, ESP8266
+//|
+//| The `random` module is a strict subset of the CPython `cpython:random`
+//| module. So, code written in CircuitPython will work in CPython but not
+//| necessarily the other way around.
+//|
+//| Like its CPython cousin, CircuitPython's random seeds itself on first use
+//| with a true random from os.urandom() when available or the uptime otherwise.
+//| Once seeded, it will be deterministic, which is why its bad for cryptography.
+//|
+//| .. warning:: Numbers from this module are not cryptographically strong! Use
+//|   bytes from `os.urandom` directly for true randomness.
+//|
+
+//| .. function:: seed(seed)
+//|
+//|   Sets the starting seed of the random  number generation. Further calls to
+//|   `random` will return deterministic results afterwards.
+//|
+STATIC mp_obj_t random_seed(mp_obj_t seed_in) {
+    mp_uint_t seed = mp_obj_get_int_truncated(seed_in);
+    shared_modules_random_seed(seed);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(random_seed_obj, random_seed);
+
+//| .. function:: getrandbits(k)
+//|
+//|   Returns an integer with *k* random bits.
+//|
+STATIC mp_obj_t random_getrandbits(mp_obj_t num_in) {
+    int n = mp_obj_get_int(num_in);
+    if (n > 32 || n == 0) {
+        mp_raise_ValueError(NULL);
+    }
+    return mp_obj_new_int_from_uint(shared_modules_random_getrandbits((uint8_t) n));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(random_getrandbits_obj, random_getrandbits);
+
+//| .. function:: randrange(stop)
+//|               randrange(start, stop, step=1)
+//|
+//|   Returns a randomly selected integer from `range(start, stop, step)`.
+//|
+STATIC mp_obj_t random_randrange(size_t n_args, const mp_obj_t *args) {
+    mp_int_t start = 0;
+    mp_int_t stop = mp_obj_get_int(args[0]);
+    mp_int_t step = 1;
+    if (n_args == 1) {
+        // range(stop)
+        if (stop <= 0) {
+            mp_raise_ValueError("stop not reachable from start");
+        }
+    } else {
+        start = stop;
+        stop = mp_obj_get_int(args[1]);
+        if (n_args == 2) {
+            // range(start, stop)
+            if (start >= stop) {
+                mp_raise_ValueError("stop not reachable from start");
+            }
+        } else {
+            // range(start, stop, step)
+            step = mp_obj_get_int(args[2]);
+            mp_int_t n;
+            if (step > 0) {
+                n = (stop - start + step - 1) / step;
+            } else if (step < 0) {
+                n = (stop - start + step + 1) / step;
+            } else {
+                mp_raise_ValueError("step must be non-zero");
+            }
+            if (n <= 0) {
+                mp_raise_ValueError("invalid step");
+            }
+        }
+    }
+
+    return mp_obj_new_int(shared_modules_random_randrange(start, stop, step));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(random_randrange_obj, 1, 3, random_randrange);
+
+//| .. function:: randint(a, b)
+//|
+//|   Returns a randomly selected integer between a and b inclusive. Equivalent
+//|   to `randrange(a, b + 1, 1)`
+//|
+STATIC mp_obj_t random_randint(mp_obj_t a_in, mp_obj_t b_in) {
+    mp_int_t a = mp_obj_get_int(a_in);
+    mp_int_t b = mp_obj_get_int(b_in);
+    if (a > b) {
+        mp_raise_ValueError(NULL);
+    }
+    return mp_obj_new_int(shared_modules_random_randrange(a, b + 1, 1));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(random_randint_obj, random_randint);
+
+//| .. function:: choice(seq)
+//|
+//|   Returns a randomly selected element from the given sequence. Raises
+//|   IndexError when the sequence is empty.
+//|
+STATIC mp_obj_t random_choice(mp_obj_t seq) {
+    mp_int_t len = mp_obj_get_int(mp_obj_len(seq));
+    if (len == 0) {
+        mp_raise_IndexError("empty sequence");
+    }
+    return mp_obj_subscr(seq, mp_obj_new_int(shared_modules_random_randrange(0, len, 1)), MP_OBJ_SENTINEL);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(random_choice_obj, random_choice);
+
+//| .. function:: random()
+//|
+//|   Returns a random float between 0 and 1.0.
+//|
+STATIC mp_obj_t random_random(void) {
+    return mp_obj_new_float(shared_modules_random_random());
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(random_random_obj, random_random);
+
+//| .. function:: uniform(a, b)
+//|
+//|   Returns a random float between a and b. It may or may not be inclusive
+//|   depending on float rounding.
+//|
+STATIC mp_obj_t random_uniform(mp_obj_t a_in, mp_obj_t b_in) {
+    mp_float_t a = mp_obj_get_float(a_in);
+    mp_float_t b = mp_obj_get_float(b_in);
+    return mp_obj_new_float(shared_modules_random_uniform(a, b));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(random_uniform_obj, random_uniform);
+
+STATIC const mp_rom_map_elem_t mp_module_random_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_random) },
+    { MP_ROM_QSTR(MP_QSTR_seed), MP_ROM_PTR(&random_seed_obj) },
+    { MP_ROM_QSTR(MP_QSTR_getrandbits), MP_ROM_PTR(&random_getrandbits_obj) },
+    { MP_ROM_QSTR(MP_QSTR_randrange), MP_ROM_PTR(&random_randrange_obj) },
+    { MP_ROM_QSTR(MP_QSTR_randint), MP_ROM_PTR(&random_randint_obj) },
+    { MP_ROM_QSTR(MP_QSTR_choice), MP_ROM_PTR(&random_choice_obj) },
+    { MP_ROM_QSTR(MP_QSTR_random), MP_ROM_PTR(&random_random_obj) },
+    { MP_ROM_QSTR(MP_QSTR_uniform), MP_ROM_PTR(&random_uniform_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(mp_module_random_globals, mp_module_random_globals_table);
+
+const mp_obj_module_t random_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&mp_module_random_globals,
+};
diff --git a/shared-bindings/random/__init__.h b/shared-bindings/random/__init__.h
new file mode 100644
index 000000000..558b5f194
--- /dev/null
+++ b/shared-bindings/random/__init__.h
@@ -0,0 +1,40 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * 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.
+ */
+
+#ifndef __MICROPY_INCLUDED_SHARED_BINDINGS_RANDOM___INIT___H__
+#define __MICROPY_INCLUDED_SHARED_BINDINGS_RANDOM___INIT___H__
+
+// This depends on shared_module because nearly all functionality is port
+// agnostic. The random module only depends on the common_hal_os_urandom or
+// common_hal_time_monotonic to seed it initially.
+
+void shared_modules_random_seed(mp_uint_t seed);
+mp_uint_t shared_modules_random_getrandbits(uint8_t n);
+mp_int_t shared_modules_random_randrange(mp_int_t start, mp_int_t stop, mp_int_t step);
+mp_float_t shared_modules_random_random(void);
+mp_float_t shared_modules_random_uniform(mp_float_t a, mp_float_t b);
+
+#endif  // __MICROPY_INCLUDED_SHARED_BINDINGS_RANDOM___INIT___H__